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Classification of flow regimes for environmental flow assessment in regulated rivers: The Huai River Basin, China
Abstract
Flow regime characteristics (magnitude, frequency, duration, seasonal timing and rates of change) play a primary role in regulating the biodiversity and ecological processes in rivers. River classification provides the foundation for comparing the hydrologic regimes of rivers and development of hydro-ecological relationships to inform environmental flow management and river restoration. This paper presents a classification of natural flow regimes and hydrologic changes due to dams and floodgates in the Huai River Basin, China, in preparation for an environmental flow assessment. The monthly natural flow regime of 45 stations in the upper and middle Huai River Basin were simulated for the period 1963–2000, based on the hydrological model SWAT (Soil and Water Assessment Tool). Six classes of flow patterns (low or high discharge, stable or variable, perennial or intermittent, predictable or unpredictable) were identified based on 80 hydrologic metrics, analysed by hierarchical clustering algorithms. The ecologically relevant climatic and geographic characteristics of these flow classes were tested for concordance with, and to strengthen, the hydro-ecological classification. The regulation of natural flow patterns by dams and floodgates changed flows at some locations within each flow class and caused some gauges to shift into another class. The research reported here is expected to provide a foundation for development of hydro-ecological relationships and environmental flow methods for wider use in China, as well as setting a new scientific direction for integrated river basin management in the Huai River Basin. Copyright © 2011 John Wiley & Sons, Ltd.
... Therefore, nine metrics are used to capture the behavior of flood events. There are the magnitude (total flood volume: R, maximum flood peak: Qpk), variability (coefficient of variation: CV), timing (timings of flood event and maximum flood peak: Tbgn and Tpk), duration (flood event duration: Tdrn), rate of changes (mean rates of positive and negative changes: RQr and RQd) and flood peak number (Npk) (Arthington et al., 2006;Kennard et al., 2010;Poff et al., 2007;Zhang et al., 2012). Table 1 summarizes the definitions of all the selected flood components. ...
... High dimensionality and multicollinearity exist among flood behavior metrics and affect the flood event classification when a 135 large number of metrics are considered (Olden et al., 2012;Zhang et al., 2012). Dimensionality reduction is to transform the high dimensional metrics into a few independent composite metrics without losing the metric information, and to reveal the major similarity characteristics among the metrics. ...
... Flood events in the same class are widely accepted to have similar 415 hydrological behaviors caused by similar meteorological or underlying surface conditions (Sikorska et al., 2015). Therefore, it is more efficient to investigate flood event changes and their cause mechanisms in a comprehensive manner than individual event analyses (Zhang et al., 2012). It is expected to provide more useful flood behavior characteristics for flood disaster management purposes (e.g., early warning and quick design of flood control plans) and provide deep insights to investigate riverine ecological and environmental response mechanisms. ...
Classification is beneficial for understanding flood variabilities and their formation mechanisms from massive flood event samples for both flood scientific research and management purposes. Our study investigates spatial and temporal variabilities of 1446 unregulated flood events in 68 headstream catchments in China at class scale using hierarchical and partitional clustering methods. Control mechanisms of meteorological and physio-geographical factors (e.g., meteorology, land cover and catchment attributes) are explored for individual flood event classes using constrained rank analysis and Monte Carlo permutation test. Results show that we identify five robust flood event classes, i.e., moderately, highly, and slightly fast floods, as well as moderately and highly slow floods, which accounts for 24.0 %, 21.2 %, 25.9 %, 13.5 % and 15.4 % of total events, respectively. All the classes are evenly distributed in the whole period, but the spatial distributions are quite distinct. The fast flood classes are mainly in the southern China, and the slow flood classes are mainly in the northern China and the transition region between southern and northern China. The meteorological category plays a dominant role in flood event variabilities, followed by catchment attributes and land covers. Precipitation factors, such as volume and intensity, and aridity index are the significant control factors. Our study provides insights into flood event variabilities and aids in flood prediction and control.
... Numerous time and frequency analysis methods are usually adopted to investigate the variations of flood event metrics at station scale, including temporal trend analysis methods (e.g., Mann-Kendall test, segmented regression model) (Shao and Campbell., 2002;Chen and Li, 2011a;Zhang et al., 2011b;Wang et al., 2015), change point tests (e.g., Pettit test, Mann-Kendall test, moving t-test) (Zheng et al., 2007;Li et al., 2008;She et al., 2017), periodicity analysis (e.g., wavelet analysis) (Anctil, 2010;Yang et al., 2018) and frequency analysis (e.g., copula analysis, entropy theory) (Zhang et al., 2011a;Singh, 2015). Most of existing studies mainly focus on flood magnitude metrics (e.g., flood volume, peak flood) and their frequencies at station scale (Milly et al., 2002a;Rogger et al., 2012;Xia et al., 2012;Ma et al., 2014;Requena et al., 2017;Merz et al., 2018;Sun et al., 2018). However, all of these findings are still difficult to reveal comprehensive variation characteristics at basin scale. ...
... Many methods have been adopted for river or catchment classification (Burn and Boorman, 1992;Rosgen, 1994;McDonnell and Woods, 2004;Ali et al., 2012), flow regime classification (Kennard et al., 2010;Zhang et al., 2012), and dam regulation assessment (Mcmanamay et al., 2016;Zhang et al., , 2017. The representative methods include multivariate and principal component analysis (Snelder et al., 2005;Zhang et al., 2012, artificial neural network (Kumar et al., 2013), and fuzzy decision tree method (Han et al., 2002;Sikorska et al., 2015). ...
... Many methods have been adopted for river or catchment classification (Burn and Boorman, 1992;Rosgen, 1994;McDonnell and Woods, 2004;Ali et al., 2012), flow regime classification (Kennard et al., 2010;Zhang et al., 2012), and dam regulation assessment (Mcmanamay et al., 2016;Zhang et al., , 2017. The representative methods include multivariate and principal component analysis (Snelder et al., 2005;Zhang et al., 2012, artificial neural network (Kumar et al., 2013), and fuzzy decision tree method (Han et al., 2002;Sikorska et al., 2015). The multivariate and principal component analyses are widely used due to their simple, fast and effective classification (Zhang et al., 2012. ...
Flood is one of the severest natural disasters in the world and has caused enormous causalities and property losses. Previous studies usually focus on flood magnitude and occurrence time at event scale, which are insufficient to contain entire behavior characteristics of flood events. In our study, nine behavior metrics in five categories (e.g., magnitude, duration, timing, rates of changes and variability) are adopted to fully describe a flood event. Regional and interannual variations of representative flood classes are investigated based on behavior similarity classification of numerous events. Contributions of geography, land use, hydrometeorology and human regulation on these variations are explored by rank analysis method. Results show that: five representative classes are identified, namely, conventional events (Class 1, 61.7% of the total), low discharge events with multiple peaks (Class 2, 5.3%), low discharge events with low rates of changes (Class 3, 18.1%), low discharge events with high rates of changes (Class 4, 10.8%) and high discharge events with long durations (Class 5, 4.1%). Classes 1 and 3 are the major flood events and distributed across the whole region. Class 4 is mainly distributed in river sources, while Classes 2 and 5 are in the middle and down streams. Moreover, the flood class is most diverse in normal precipitation years (2006, 2008–2010 and 2015), followed by wet years (2007, 2013–2014), and dry years (2011 and 2012). All the impact factor categories explain 34.0%–84.1% of individual flood class variations. The hydrometeorological category (7.2%–56.9%) is the most important, followed by geographical (1.0%–6.3%), regulation (1.7%–5.1%) and land use (0.9%–2.2%) categories. This study could provide new insights into flood event variations in a comprehensive manner, and provide decision-making basis for flood control and resource utilization at basin scale.
... The Ecological Limits of Hydrologic Alteration framework (ELOHA; established a methodological framework that allowed water managers and scientists to build ecohydrological models at broad scales and use ecological responses to flow alterations for modeling e-flows. There are many applications of ELOHA worldwide, including in the USA (Buchanan et al., 2013;Sanderson et al., 2012), China (Zhang et al., 2012), and Australia . ...
... River flows will decrease in many regions of the world (Blöschl et al., 2019;Stefanidis et al., 2018;Zhang et al., 2012). Even the most optimistic climate change scenarios predict that by the next few decades water availability in the Mediterranean will exhibit a significant decline with severe implications for freshwater-related services (Jorda-Capdevila et al., 2019). ...
... Along with successful applications in assessing environmental flow (Poff et al., 2010), hydrological classifications (Peñas et al., 2014), and patterns of hydrological alteration (Penas & Barquín, 2019;Zhang, Zhai, et al., 2015;Zhang, Xia, et al., 2018), flow regime metrics are widely accepted to interpret eco-hydrological interaction and explore hydrological-ecological response mechanisms (Poff et al., 2010;Richter et al., 2003). River classification is a very valuable tool to partition of homogeneous classes at regional scale from large number of stations (Penas and Barquín, 2019;Poff et al., 2010;Zhang et al., 2012;Zhang, Fu, et al., 2015;Zhang, Zhai, et al., 2015). Zhang, Zhai, et al. (2015) applied river classification to identify the four main classes of flow regime alterations in the regulated Huai River Basin in China. ...
... Flow regime metrics have been widely used in eco-hydrology and provide a comprehensive summary of streamflow characteristics, including magnitude, frequency, duration, timing and variability (Bunn & Arthington, 2002;Zhang et al., 2012. In our study, 18 flow regime metrics are selected, including eight metrics describing flow magnitude (average flow condition: four metrics; low flow condition: two metrics; high flow condition: two metrics); two metrics describing runoff frequency (low flow condition: one metric; high flow condition: one metric); two metrics describing runoff duration (low flow condition: one metric; high flow condition: one metric); two metrics describing the timing of runoff (low flow condition: one metric; high flow condition: one metric); and four metrics describing the variability of streamflow. ...
Traditional impact assessments of future changes on flow regimes mainly focus on streamflow magnitude and static land use, which are insufficient to capture entire characteristics of flow regime variations and future land use change. In this study, 18 flow regime metrics are adopted to fully characterize the streamflow hydrograph. The future changes are considered, including land use scenario in 2025 predicted by the Cellular Automata‐Markov (CA‐Markov), and climate change scenarios under three representative concentration pathways (RCPs) (i.e., RCP2.6, RCP4.5, and RCP8.5) obtained from five general circulation models (GCMs) for the period 2021–2030. Regional impacts of future land use and climate changes on flow regimes in the Yellow River Source Region are simulated and identified using distributed hydrological modeling and spatial classification. Results show that the increases in unused land (14.16%), and decreases in grassland (2.54%), glacier and snow cover (62.85%) are remarkable for the period 1980–2025. The flow regimes will be highly impacted in the source region for the RCP2.6 and RCP8.5 scenarios, but in the middle stream and downstream regions for the RCP4.5 scenario. Both the future land use and climate changes will increase flow magnitude for most regions, but their impacts on other flow regime metrics are not homogeneous. The climate change will play the dominant role in the flow regime variations, while the land use change will highly affect mean pre‐flood runoff, frequency and duration of high flow events, and mean rates of positive and negative changes.
... These hydraulic structures have substantially altered the natural variability of flow regimes and the native transport mechanisms of materials in river-lake systems (Lu, Lei, Yang, Tang, & Miao, 2018), which has resulted in discontinuous flow in some watercourses and the consequent deterioration of the freshwater environment (Y. Zhang et al., 2012). The flow regulation's involvement in river-lake systems influences the effects of seasonal floods as well as seasonal fluctuations of water levels, and contributes to habitat degradation, which threatens the diversity of fauna and flora (Gao, Xie, & Zou, 2020;Mallik & Richardson, 2009;Wu et al., 2019). ...
The hydrodynamic processes in large river–lake systems and their responses to flow regulation represent regionally unique and highly significant issues. This study presents the implementation, validation and application of a two-dimensional hydrodynamic model to a system comprising a section of the Huai River and Hongze Lake, China. The validated model enabled the identification of hydrodynamic characteristics by analysing the flow patterns under the influence of the local flow regulation. Effective flow regulation measures during flood period reduced the retention time of floodwater in the lake and contributed to a low-velocity current field in the northern part of the river–lake system. Throughout the non-flood period, a distinctive flow pattern emerged due to persistent easterly winds, resulting in a dual circulation pattern in the interconnected region between the northern and central segments of the system. The investigation of flow patterns revealed the creation of stagnant water zones in the northern sector of Hongze Lake. Distributing a substantial portion of outflow discharge to the Erhezha gate could lead to an expansion of the flood passing area by scenario analysis. Simultaneously, implementing intermittent control over the Erhezha gate drainage effectively heightened the current velocities in the stagnant water zone. The deliberate allocation of outflow discharge has a substantial impact on the flow dynamics within a vast river–lake system during the flood season, which carries significant research potential in enhancing the local water self-purification capacity and water quality.
... (3) prediction and model parameterization in ungauged catchments [10][11][12][13][14][15][16][17][18]; (4) predictions under changed flow conditions [6,11,[19][20][21][22]; (5) assessment of environmental flows [23][24][25][26][27]; and (6) eco-hydrologic classification [28,29]. ...
Catchment classification plays an important role in many applications associated with water resources and environment. In recent years, several studies have applied the concepts of nonlinear dynamics and chaos for catchment classification, mainly using dimensionality measures. The present study explores prediction as a measure for catchment classification, through application of a nonlinear local approximation prediction method. The method uses the concept of phase-space reconstruction of a time series to represent the underlying system dynamics and identifies nearest neighbors in the phase space for system evolution and prediction. The prediction accuracy measures, as well as the optimum values of the parameters involved in the method (e.g., phase space or embedding dimension, number of neighbors), are used for classification. For implementation, the method is applied to daily streamflow data from 218 catchments in Australia, and predictions are made for different embedding dimensions and number of neighbors. The prediction results suggest that phase-space reconstruction using streamflow alone can provide good predictions. The results also indicate that better predictions are achieved for lower embedding dimensions and smaller numbers of neighbors, suggesting possible low dimensionality of the streamflow dynamics. The classification results based on prediction accuracy are found to be useful for identification of regions/stations with higher predictability, which has important implications for interpolation or extrapolation of streamflow data.
... The SWAT model is one such model that is extensively cited in the literature and has been adapted by many researchers to study the impacts of LULC changes and climate variability on large and small watersheds around the world [23,24]. In recent studies, the SWAT model was employed to assess the effects of LULC on hydrology [7,22,25,26]. It was applied to the Zanjanrood basin in Iran [13], the Upper Shire River basin in Malawi [27], the San Pedro watershed in Mexico [28], the Upper Du watershed in China [29] and the Hiranyakeshi watershed [19]. ...
Land use/land cover, along with climate variability, play vital roles in hydrological functionality of catchments and are leading threats to inter-related hydrological processes. In the current study, a physically distributed Soil and Water Assessment Tool model is used to investigate the impact of historical changes on the hydrologic response of the Damodar catchment (Jharkhand, India) in terms of inflow to the Panchet reservoir. The model was validated for the monthly runoff and inflow at the outlets of four watersheds and three reservoirs in the Damodar catchment before the assessment of changes in inflow at the Panchet reservoir was performed. The analysis of land cover thematic maps prepared using satellite images of Landsat 4, 5 and 7 showed that from 1972 to 2001, the land cover in the Damodar catchment changed considerably. The interpretation of land cover results indicates that significant increases in settlements (140%), waterbodies (98.42%) and agricultural land (26.71%), along with decreases in wasteland (32.63%) and forest (15.28%), occurred due to development. The Mann–Kendall test was used for measuring the rainfall and temperature for the Damodar catchment, which showed that this region became drier during 1970–2005, with decreases in the annual rainfall and increases in the mean temperature. A simulated hydrological impact under land cover dynamics and climate variability in the historical time frame of 1970–2000 using the model revealed a gradual increase of 26.16% in the Panchet reservoir inflow. The study revealed that the increased inflow is relatively greater under the influence of climate variability due to changes in rainfall and temperature, rather than land cover, that were observed over the region.
... SM is highly sensitive to rainfall; therefore, the study period selected for this research was ideal because it ensured that CLDAS SM products could capture this phenomenon. In addition to rainfall, droughts and floods in the Huaihe River Basin are significantly impacted by climate variations, intense anthropogenic activities, and changes in land topography [58], [59], [60]. Precipitation variability can increase the risk of soil loss [31]. ...
Soil moisture (SM) is an important parameter in all environments because it affects the relationship between the land surface and atmospheric processes. Therefore, finding products that can accurately measure SM is critical to improving drought management. The objective of this study was to investigate the accuracy of satellite data from SM produced by the China Meteorological Administration Land Data Assimilation System (CLDAS), focusing on the Huaihe and Heihe River basins in China, as both are prone to drought. To verify the accuracy of the daily surface data SM, measurements were obtained from 34 meteorological stations between January and December 2016. In addition, CLDAS measurement data were collected at a depth of 10 cm and 40 cm and compared with observed soil moisture measurements (OBS SM). The results show that the agreement of CLDAS SM with OBS was R > 0.66 at 10 cm and R > 0.47 at 40 cm in the Huaihe River Basin. R > 0.63 at 10 cm and R > 0.44 at 40 cm was observed in Heihe River Basin.
... Human activities have changed the flow regimes. Numerous studies have reported that anthropogenic activities have significantly impacted the ecosystem, with extensive changes occurring in river systems and biodiversity [20][21][22][23][24][25]. Recent pressure on the freshwater ecosystem has caused the extinction of about 20% of freshwater species worldwide. ...
Hydrological regimes influence an aquatic ecosystem’s biotic composition, structure, and functioning. But construction of dams or anthropogenic activities substantially alter the hydrologic regimes. In this study, we used a method named as the “Indicators of Hydrologic Alteration” to examine the degree of hydrologic alteration at seven flow gauge stations in the Mangla watershed. The assessment of alteration is carried out according to the Range of Variability (RVA). This method relies on analyzing hydrologic data obtained from existing measurement points (e.g., stream gauges) within an ecosystem or model-generated data. We used 33 parameters categorized into 5 groups based on magnitude, duration, frequency, timing, and rate of change to characterize hydrologic variation within a year statistically. We then examine the hydrologic perturbations by comparing the measure of central tendency and dispersion for each parameter between the “pre-impact (1967–1994)” and “post-impact (1995–2014)” periods. The results show that within the Mangla watershed, the high alteration was noted in the magnitude of monthly flows and extreme flows at Azad Pattan, Gari Habibullah, Palote and at Muzafarabad stations. The flow at Domel and Kohala stations are found in low hydrological alteration among all groups of indicators. The study indicates that Neelum Basin at Muzaffarabad has significantly high alteration with maximum negative values. On the other hand, a high frequency of alteration observed in the monthly flows and extreme water conditions. Overall, a moderate alteration is observed in the whole watershed, which may produce adverse effects on the aquatic ecosystem of the Mangla watershed.
... As an emerging tool for assessing the relationship between hydrologic and ecological development changes, the ELOHA framework has been widely used in practice, and several studies have shown that dams and floodgates significantly disturb ecologically relevant hydrologic indicators, especially in the downstream areas of regulated rivers where dam disturbances have varying levels of impact on riparian and aquatic vegetation, as well as species density and community composition of aquatic organisms such as fish and macroinvertebrates Ben et al., 2014;Bower et al., 2022;Zhang et al., 2012). A negative correlation between riparian coverage in regulated rivers and the flow recovery process is as expected (Mcmanamay et al., 2013), and rates of loss of channel width, depth, and river velocity are steepest at low flows, largely explaining the strong nonlinear correlation (Rosenfeld, 2017). ...
With the accelerated development of urbanization, rivers in urban areas have become the most closely synergized water ecosystem between human activities and natural processes. To achieve the restoration goal of using hydrological regime change-ecological response relationship to advance the sustainable development of regulated river ecosystems, this study collected ecohydrological data at four tributaries of the Wei River system (Ba River, Chan River, Feng River, and Hei River) at a total of 24 stations in October 2020 and June 2021. Taking ecological flow as hydrological parameter and zooplankton as indicator organism, combined with habitat data scored on-site, the indicator system of zooplankton index of biological integrity and comprehensive habitat quality index was established to explore the hydrological-ecological response relationship in a multi-dimensional way. The results showed that during the ebb stage, the ecological health of the Feng River was better overall, with an average ecological flow value of 267.09 ± 348.62. The ecological health of the Hei River was the worst, with an average ecological flow value of 37.80 ± 38.80. During the abundant water period, the ecological health of the Chan River was optimal with an average ecological flow value of 189.25 ± 190.10, while the ecological health of the Hei River remained unimproved, but the average ecological flow value increased by 283.12 ± 197.76. There was a clear negative correlation relationship between the comprehensive habitat quality index and ecological flow. The correlation between zooplankton index of biological integrity and ecological flows is extremely strong and threshold values exist, but there is strong heterogeneity in the interaction of disturbance factors across water systems, which may not provide a predictable response to flow changes. This study aims to provide a case reference for flow management in watersheds that also lack long-time series hydrological data and to contribute new thinking to the wide application of the hydrological-ecological response relationship.
... A good number of researchers have shown that flow modification is one of the emerging challenges since it changes the downstream flow regime in terms of total flow, size, timing, length, rate of change, and water quality Huang et al. 2019;Amenuvor et al. 2020;Du et al. 2020;Pal and Sarda 2020;. As a result, it can reduce the connection of the main channel with the flood plain, and it not only arrests the water supply to the flood plain but also limits the natural dispersion of fish and macroinvertebrate species toward the flood plain for sustaining the flood plain biodiversity (Rolls et al. 2012;Bunn and Arthington, 2002;Zhang et al. 2012). Li et al. (2017) documented since 1991 to 2009, the average flow of Southeast Asia's Mekong river was decreased by 82%. ...
A good number of researchers investigated the impact of flow modification on hydrological, ecological, and geomorphological conditions in a river. A few works also focused on hydrological modification on wetland with some parameters but as far the knowledge is concerned, linking river flow modification to wetland hydrological and morphological transformation following an integrated modeling approach is often lacking. The current study aimed to explore the degree of hydrological alteration in the river and its effect on downstream riparian wetlands by adopting advanced modeling approaches. After damming, maximally 67 to 95% hydrological alteration was recorded for maximum, minimum, and average discharges. Wavelet transformation analysis figured out a strong power spectrum after 2012 (damming year). Due to attenuation of flow, the active inundation area was reduced by 66.2%. After damming, 524.03 km2 (48.9% of total pre-dam wetland) was completely obliterated. Hydrological strength (HS) modeling also reported areas under high HS declined by 14% after post-dam condition. Wetland hydrological security state (WSS) and HS matrix, a new approach, are used to explore wetland characteristics of inundation connectivity and hydrological security state. WSS was defined based on lateral hydrological connectivity. HS under critical and stress WWS zones deteriorated in the post-dam period. The morphological transformation was also well recognized showing an increase in area under the patch, edge, and a decrease in the area under the large core area. All these findings established a clear linkage between river flow modification and wetland transformation, and they provided a good clue for managing wetlands.
... Topography and climate characteristics affect rivers in the vast territory of China (Zhang et al., 2011). Land use patterns and urbanization impact river water quality and ecology in a dam-dominated basin (Luo et al., 2020). ...
Dominant functions usually vary greatly in different reaches of mountainous rivers and are influenced by different adjacent land uses. Assessing river health based on dominant functions is of great practical value to river management. To reveal the health status of different reaches in Beijing’s northern mountainous rivers, 60 investigated plots (river length 38.1 km) were surveyed in 2016 in the Huaijiu River, which is a typical mountainous river in northern Beijing, and a hierarchy-comprehensive analysis method was employed. Based on the degree of human influences, the Huaijiu River could be classified into six types, including natural reaches, near-natural reaches, artificial bank plant reaches, artificial bank ornamental plant reaches, artificial bank sparse plant dry-stone reaches and artificial bank masonry reaches. The river health assessment index system was established based on flood control, landscape, hydrology and water quality, and ecological functions. The analytic hierarchy process (AHP) was used to determine the weights of the function layer and indicator layer. The assessment results showed that healthy, subhealthy, slightly damaged, damaged and severely damaged plots accounted for 20.0%, 26.7%, 26.7%, 15.0% and 11.6% of the total plots, respectively. In summary, all plots in natural reaches, artificial bank plant reaches and artificial bank ornamental plant reaches were either healthy, subhealthy or slightly damaged. Plots in artificial bank masonry reaches were either subhealthy, slightly damaged, damaged or severely damaged, accounting for 9.1%, 27.3%, 27.3% and 36.4% of the total plots, respectively. The study proposed a method to assess mountainous river health based on dominant functions, which is a multiobjective approach and is not based solely on natural river functions. The assessment method is appropriate for the socioeconomic development and management of river basins.
... The number of classes was verified based on an analysis of the geometry of the dendrogram and the plot of the linkage distance curve. The methods presented above are commonly used in hydro-meteorological research (Berhanu et al., 2015;Graf and Wrzesiński, 2020;Isik and Singh, 2008;Zhang et al., 2012). ...
Main aim of the study was to determine the temporal and spatial patterns of relations between monthly and annual average river flow (RF) and water temperature (WT) for 53 rivers in Poland. The research made use of monthly and annual WT and RF for 88 water gauges for the period 1971-2015. Correlations were established using the Spearman's rank correlation coefficient and the similarity of RF-WT relations was determined using the Ward's hierarchical grouping. It was demonstrated that correlations between average annual RF and WT were negative (for >85% of water gauges) and statistically significant (p<0.05) only for 30% of water gauges. It was confirmed that the studied RF-WT relations underwent seasonal changes. Positive correlations were clearly predominant in the winter months, while from April to September these relations were negative and statistically significant. The RF-WT relations were also characterized by spatial differences and this had been confirmed by separation of seven groups of water gauge profiles distinguished with the help of the Ward's hierarchical grouping method. The strongest RF-WT relations were apparent in the case of mountainous rivers, for which snow melt supply and summer rainfall supply were predominant, and lakeland rivers, which had a considerable share of groundwater supply. These were classified as cold rivers, as opposed to the cool rivers in the lowland belt, for which the RF-WT relations were the weakest. The results obtained may contribute to the elaboration of an appropriate management strategy for river ecosystems, which are assigned important economic and environmental functions.
... A driving force such as population growth, resulting in land use change, potential growth of industries and extraction of water for industrial operations, coupled with climate change will create major stress on the existing ecosystem. Determination of the ecological threshold for flow variability is an intricate and tedious procedure, and many researchers have focused on this research area (Gain et al., 2013;Ghanbarpour et al., 2013;Jiang et al., 2014;Knight et al., 2008;Konrad et al., 2008;Mathews & Richter, 2007;Meijer & Beek, 2011;Richter et al., 2011;Zhang et al., 2011). However, there has been no study carried out in Brunei Darussalam to identify E-flows which would keep its rich biodiversity intact. ...
The concept of environmental flows and its application and enforcement is a main challenge in several developing countries. The services and benefits derived from the ecosystem are indispensable for sustaining the livelihood of people particularly living in coastal areas. Decision-makers often ignore ecosystems when referring to water allocation, as the supporters of ecosystems are less vocal as compared to other stakeholders. This study focuses on establishing guidelines for maintaining the minimum amount of flow known as environmental flow of Brunei River in Brunei Darussalam for the sustainability of its rich ecosystem. In this study, the flow of the river was simulated based on land use, climate change, and potential growth of industries using a Water Evaluation and Planning System as a computing tool. The study finds that the months of March and June (1.48 and 3.92 m ³ /s) are more vulnerable to low flow. It recommends a threshold value of 2.7 m ³ /s for the environmental flow of Brunei River essential to preserve its rich and diversified ecosystem.
... To date, China has made several notable achievements, including vegetation changes and their effects on runoff, sediment, soil moisture variation and dissipation, and hydrological cycles (Wang et al., 2015;Zhou et al., 2015;Feng et al., 2016). Further, in ecohydrology related studies of aquatic systems, remarkable contributions have been made to the impact mechanisms of flow regimes, associated water quality processes on aquatic communities, and ecohydrological process simulations based on the theories of river continuum, flood pulse, and natural flow paradigm (Zhang et al., 2012;Chen et al., 2013;Xu et al., 2013;Zhu et al., 2018). These contributions have been practically applied to control cyanobacterial blooms in the Taihu Lake, simulate fish habitats under flow regime variations, and ecologically regulate the Three Gorges Dam. ...
In recent decades, the ecohydrology discipline was developed to provide theoretical and technical foundations for the protection and restoration of complex ecological systems (e.g., mountains, rivers, forests, farmlands, and lakes), and to further ecological civilization construction and green development in China. In this study, the progress and challenges of the ecohydrology discipline are elaborated, and the future development directions are proposed according to international scientific frontiers and national ecological civilization construction demands. Overall, the main discipline directions are to develop new ecohydrological monitoring methods, to comprehensively understand ecohydrological mechanisms and their basic theories, to promote integration of multi-scale and multi-variable models by considering both terrestrial and aquatic ecosystems, and to encourage multidisciplinary integration, particularly with the social sciences. Furthermore, the future research interests in China include: combining multi-source information, constructing comprehensive monitoring systems, studying spatiotemporal patterns of key ecohydrological variables and their variation characteristics, developing integrated models of ecological, hydrological, and economic processes, estimating their uncertainty; and conducting interdisciplinary studies that include the natural and social sciences. The application prospects in China are further explored for a variety of ecosystems, including forests, grasslands, rivers, lakes, wetlands, farmlands, and cities. This study will provide a reference to support the development of the ecohydrology discipline in China, and will provide a solid theoretical and technical foundation for the implementation of national ecological civilization construction.
... Existing estimates of flood behavior metrics are usually implemented using statistical analysis (e.g., multiple linear regression, multiple logtransformed linear regression, regression tree ensemble) (Qamar et al. 2016;Visessri and McIntyre 2016;, and hydrological modelling (Bai et al. 2009;Pechlivanidis and Arheimer 2015). However, these applications have been mainly in water resources management and ecological flow assessment at coarser time scales (e.g., daily/ monthly/intra-annual/inter-annual) (Li et al. 2010a;Shu et al., 2012;Zhang et al. 2012;Singh et al. 2014). As for flash flood management, it still remains a key issue to reliably reproduce and forecast major flash flood behavior metrics for providing further supplementary information in addition to hydrographs. ...
China frequently suffers from considerable and disastrous flash floods with wide areal coverage and high frequency. Obtaining useful information to support flash flood management and decision-making is challenging for massive flash flood events that vary greatly in spatio-temporal characteristics. In this study, hydrological modelling approach (CNFF) and cluster analysis were integrated to assess simulation reliability of entire flash flood processes including both hydrographs and behavior characteristics in a manner of similarity classification, rather than at event scale. A total of 207 hourly events from 13 mountainous catchments with diverse physiographic and meteorological characteristics across China were selected for study. Representative flash flood types were classified using normalized hydrographs with diverse spatio-temporal patterns by k-means clustering algorithm. For individual flash flood types, simulation reliability of CNFF was assessed in capturing corresponding hydrographs, seven behavior metrics measuring flash flood magnitude, intensity, occurrence time, flood timescale, rates of change and variability, and their uncertainties. Results showed that three (fast, intermediate and slow) flash flood types were identified from all the flash flood events with overall average silhouette index of 0.45. Hourly hydrographs of three flash flood types were well reproduced by CNFF, with absolute average relative error of runoff within 15% and Nash-Sutcliffe Efficiency above 0.55. All the behavior metrics were the most accurately reproduced for slow flash flood type with the least average relative root-mean-square error (0.30), followed by intermediate (0.52) and fast (0.58) types. Moreover, the slow flash flood type had the most reliable but greatest uncertainty interval of both hydrograph and behavior metrics, with average relative interval length being 1.24 and 71.96%, and 93.10% and 100% of observations contained in 95% confidence interval, respectively. This study provided efficient and detailed information for flash flood management, and extended application scope of hydrological models to encompass flash flood types and behavior metrics.
... River water quality is influenced by both natural process and anthropogenic factors in the highly regulated river basin, sometimes even dominated by anthropogenic factors (Todd et al. 2012;Best 2018). The majority of the world's large river systems is affected by dams and sluices (Nilsson et al. 2005;Zhang et al. 2012b;Grill et al. 2015;Best 2018). The construction of dams and sluices unavoidably breaks down the river continuum, alters the river flow regime, changes running water into still water, and induces a long water residence time (Wei et al. 2009;Habets et al. 2018). ...
Dams and sluices break down the river continuum, alter the river hydrological regime, and intercept the migration processes of nutrients and pollutants. The regulation of dams and sluices will have great impacts on water quality characteristics in the river basin. In this study, variable fuzzy pattern recognition model (VFPR), principal component analysis/factor analysis (PCA/FA), and the absolute principal component score-multiple linear regression (APCS-MLR) were used to assess the water quality and identify the potential pollution sources in a highly regulated river of Northeast China. A set of water quality variables at three stations were measured from January 2015 to August 2017. The water quality assessment results showed that there were spatial and temporal variations of water quality and the total nitrogen (TN) and fecal coliforms (F. coli) were the major pollution factors of the study river section. Four pollution sources, including industrial effluent source, domestic sewage source, meteorological factor and atmospheric deposition source, and agricultural non-point source, were identified in dry and wet seasons using the PCA/FA method. The APCS-MLR results showed that the industrial effluent source was the main pollution source in dry seasons and had a decrease in wet seasons. While the mean contribution of the domestic sewage source had an increase in wet seasons, influenced by the sewage overflow and the flushing of pollutants during the extreme precipitation, the construction of dams decreased the flow obviously in wet seasons and increased in dry seasons. The increase in pollutants caused by storm runoff and the reduction of dilution water in the river channel could be the main reason for the water quality degradation in wet seasons.
... The number of classes was determined based on the analysis of geometry of the dendrogram and the plot of the linkage distance curve. The aforementioned methods are commonly used in hydro-meteorological studies [41][42][43][44][45]. In the statistical analysis of the results obtained the Statistica (StatSoft) software was applied. ...
The study determined water temperature trends of rivers in Poland in the period 1971–2015, and also their spatial and temporal patterns. The analysis covered daily water temperature of 53 rivers recorded at 94 water gauge stations and air temperature at 43 meteorological stations. Average monthly, annual, seasonal and maximum annual tendencies of temperature change were calculated using the Mann–Kendall (M–K) test. Regional patterns of water temperature change were determined on the basis of Ward’s hierarchical grouping for 16 correlation coefficients of average annual water temperature in successive 30-year sub-periods of the multi-annual period of 1971–2015. Moreover, regularities in monthly temperature trends in the annual cycle were identified using 12 monthly values obtained from the M–K Z test. The majority of average annual air and water temperature series demonstrate statistically significant positive trends. In three seasons: spring, summer and autumn, upward tendencies of temperature were detected at 70%–90% of the investigated water gauges. In 82% of the analysed rivers, similarity to the tendencies of change of monthly air temperature was concluded, with the climatic factor being recognised as of decisive importance for the changes in water thermal characteristics of the majority of rivers in Poland. In the winter months, positive trends of temperature were considerably weaker and in general statistically insignificant. On a regional scale, rivers with a quasi-natural thermal regime experienced temperature increases from April to November. In the other cases, different directions of change in river water temperature (RWT) were attributed to various forms of human impact. It was also found that for the majority of rivers the average annual water temperature in the analysed 30-year sub-periods displayed upward trends, statistically significant or close to the significance threshold. Stronger trends were observed in the periods after 1980, while a different nature of water temperature change was detected only in a couple of mountainous rivers or rivers transformed by human impact. In the beginning of the analysed period (1971–2015), the average annual water temperature of these rivers displayed positive and statistically significant trends, while after 1980 the trends were negative. The detected regularities and spatial patterns of water temperature change in rivers with a quasi-natural regime revealed a strong influence of climate on the modification of their thermal regime features. Rivers characterised by a clearly different nature of temperature change, both in terms of the direction of the tendencies observed and their statistical significance, were distinguished by alterations of water thermal characteristics caused by human activity. The results obtained may be useful in optimising the management of aquatic ecosystems, for which water temperature is a significant indicator of the ongoing environmental changes
... For instance, most economic models are yet to value the services provided by freshwater ecosystems. There are positive examples, e.g., in the USA (Kendy et al., 2012) or China (Zhang et al., 2012), but water management practices are often fragmented, leading to lost synergies, poor trade-offs, and are not readily transferable (Boelee, 2011). Even though central to sustainable intensification of agriculture, these farm water management strategies are currently insufficiently represented among international development policies (Rockström and Falkenmark, 2015;Searchinger et al., 2018). ...
A sustainable and just future, envisioned by the UN's 2030 Agenda for Sustainable Development, puts agricultural systems under a heavy strain. The century-old quandary to provide ever-growing human populations with sufficient food takes on a new dimension with the recognition of environmental limits for agricultural resource use. To highlight challenges and opportunities toward sustainable food security in the twenty first century, this perspective paper provides a historical account of the escalating pressures on agriculture and freshwater resources alike, supported by new quantitative estimates of the ascent of excessive human water use. As the transformation of global farming into sustainable forms is unattainable without a revolution in agricultural water use, water saving and food production potentials are put into perspective with targets outlined by the Sustainable Development Goals (SDGs). The literature body and here-confirmed global estimates of untapped opportunities in farm water management indicate that these measures could sustainably intensify today's farming systems at scale. While rigorous implementation of sustainable water withdrawals (SDG 6.4) might impinge upon 5% of global food production, scaling-up water interventions in rainfed and irrigated systems could over-compensate such losses and further increase global production by 30% compared to the current situation (SDG 2.3). Without relying on future technological fixes, traditional on-farm water and soil management provides key strategies associated with important synergies that needs better integration into agro-ecological landscape approaches. Integrated strategies for sustainable intensification of agriculture within planetary boundaries are a potential way to attain several SDGs, but they are not yet receiving attention from high-level development policies.
... Unnatural flow alternations negatively influence ecosystems [9][10][11]. Since 2006, GoC has issued many relevant guidelines or standards to promote the sustainable development of water resources (Table 1). ...
The rapid economic development of river basins depends on the excessive use of water resources. China experienced a rapid development of hydropower projects in the last two decades and thus faces many ecological and environmental issues, especially in ecologically sensitive areas. Environmental flow is an important management tool that requires attention in the environmental impact assessment of hydropower projects. Environmental flows are of great significance for maintaining river structures and protecting the health of both aquatic ecosystems and human sustainable livelihoods. Although the government authorities have done much work in this area and attempted to consider technical requirements to address the negative externalities of hydropower projects, there are still defects in the basic procedures, calculation methods, and ultimately implementation process from policy to operationalization in terms of environmental flows. The official standards for environmental flows assessment mainly appear in two documents: 1. specification for calculation of environmental flow in rivers and lakes; and 2. code for calculation ecological flow of hydropower projects. This paper reviewed the overarching framework of the two documents and then summarized their fitness in terms of environmental flows implementation in hydropower projects. The research status of environmental flows and future directions for China were also proposed in this paper.
... The so-called Colwell's indices (Colwell, 1974) are a commonly used tool for the analysis of seasonal changes in the hydrological regimes of rivers, which provide a simple measure of the repeatability of hydrometeorological phenomena against time. They are used to study the repeatability of such phenomena as flow (Gan et al., 1991), flow velocity (Riddell and Leggett, 1981), rainfall seasonality (Miller, 1984) and the classification of river catchments according to their flow regime (Kennard et al., 2010;Webb et al., 2012;Zhang et al., 2012). Therefore, it can be assumed that Colwell's indices will depend on the physiographic characteristics of the catchment and the course of meteorological phenomena. ...
The classification of river catchments according to their hydrological regime is crucial elements of regionalisation. In absence of hydrological data, the regionalisation of catchment method may be used to asses many flows characteristics like regime or design flow and thus provide help in the analysis of hydrological and ecological processes and also in the management of water resources. Correct clarification of catchments requires knowledge about the main factors that influence on river regime, like meteorologic conditions, land cover/land use, geology, soil properties terrain features, human activities. The aim of the study was to analyse the relationship between selected catchment attributes along with precipitation climatology and seasonality of mean flows (MQ) in the mountainous rivers in the Upper Vistula basin (the biggest and the most important river in Poland) and regionalisation catchments based on seasonality index. To achieve the objective of the study, we concentrated on the mountain stream and river catchments that are regionalised to the Upper Vistula basin (all of which are Vistula tributaries) and we employed the Colwell's seasonality index in an attempt to clear up the said ecohydrological measures. The study confirmed that in mountainous catchments, where response time to rainfall is shorter due to larger slopes, higher seasonality of mean monthly discharges, as expressed by the seasonality index M, is observed. In this case, variability of seasonal rainfall affected seasonality of MQ. In case of smaller slopes and large forest cover and catchment areas, seasonality of flows was lower. The innovative aspect of the presented study is the attempt to correlate the Colwell's seasonality index with the physiographic and meteorological characteristics of the catchment. Until now, the characteristics of the catchments have been used as factors differentiating the hydrological regime of the catchments, thus allowing for agglomeration of similar catchments. Our results foster better understanding of the natural processes in the river basin, which definitely would help in better management of the environment and its relationship with huge number of people living there and depend on it. These results show that the regression tree methods based on CART algorithm can be used as effective tool for classification of catchments.
... Water Resources Research particular hydrological nature through flow regime classification (Arthington et al., 2018). Arthington et al. (2018) provide a review of how this along with associated derivative frameworks have been implemented in the USA (Buchanan et al., 2013;Kendy et al., 2012;Reidy Liermann et al., 2012;Sanderson et al., 2012), Spain (Belmar et al., 2011), China (Zhang et al., 2012), Australia James et al., 2016;Mackay et al., 2014) and Africa (O'Brien et al., 2017). ...
Natural hydrological regimes encompass varying seasonal flow characteristics that provide fish with cues and opportunities for upstream spawning migrations, but these flows are often modified/absent in regulated rivers. Compensatory artificial flows (freshets) can be released from reservoirs to replicate these characteristics, but studies testing their effectiveness are limited. To address this, river‐resident brown trout, a species known to undertake spawning migrations, were manually tracked using radio telemetry in a regulated upland river in northern England in response to 11 freshet releases of differing timing, magnitude and duration. Spawning migrations were not observed because extent of movement during freshets was generally small and the pattern of movement (i.e. directionality and relocation indices) was comparable between impact/control reaches. Movements during freshets were comparable with those observed the days immediately before/after and were small relative to the entire tracking period. In conclusion, freshets characteristic of those recommended to produce “naturalized” autumn/winter flow elevations did not stimulate/facilitate spawning migrations of river‐resident brown trout under the given seasonal conditions. Outside freshets, longer unidirectional movements occurred during low flow periods and elevated river level due to rainfall, including during periods of reservoir overtopping. Notwithstanding, fish in experimental reaches were significantly more active (total distance moved) and occupied a larger extent of river (range during freshet) than those in control reaches during short‐duration freshets. Therefore, during dry years/when (autumn/winter) reservoir overtopping events are unlikely, small‐magnitude freshets providing flows that allow fish short opportunities to search for/find superior local habitat whilst minimising total water released are recommended.
... The Shaying River (a typical dam-controlled river) is the largest tributary of the Huaihe River in China (Zhang et al. 2012, Zuo et al. 2016b). It has several features relevant to this study, including numerous dams, frequent water pollution accidents and prominent contradiction between flood control and pollution prevention (Wang 2014). ...
To solve the contradiction between regulation and protection of the water ecological environment in a dam-controlled river, it is necessary to identify the main influencing factors of that environment and the interactions between the water quantity, quality and ecology. In this paper, the redundancy analysis (RDA) technique is used to identify the key influencing factors of water eco-environment in the Shaying River, China. The multivariate nonlinear quantization method is used to quantify the interactive relationship between water quantity, water quality and water ecology, and a quantitative model of the dam-controlled river eco-environment is constructed. The results show the relative importance of the various environmental factors. The Shannon-Wiener diversity index is used to assess phytoplankton, zooplankton and benthos (P-SWI, Z-SWI and B-SWI, respectively). The R² of the quantization models for P-SWI, Z-SWI and B-SWI in the fitting phase were 0.81, 0.72 and 0.66, respectively, and, in the validation phase, they were 0.36, 0.30 and 0.41, respectively. The results of this study can provide reference and support for the environmental regulation of dam-controlled rivers.
... Diverse flow regimes such as (magnitude, duration, timing, and frequency) among the rivers have been observed due to human activities. It was reported from various studies that the anthropogenic activities significantly affect the ecosystem and extensive modifications had occurred in the river systems and biodiversity Abe and Joseph, 2015;Dudgeon, 2010;Arthington et al., 2012;Butchart-Kuhlmann et al., 2018;Uday Kumar and Jayakumar, 2018a). ...
The present study has been taken up to quantify the impacts of the anthropogenic activities on the hydrology of the middle and lower stretches of the Krishna River over the past sixty years. The Flow Health (FH) method which is based on the Range of Variability Approach (RVA) is used to quantify the hydrological alteration (flow changes) of different flow characteristics. The flow characteristics of pre- and post-dam impact periods are compared and evaluated to understand the ecologically sensitive streamflow parameters. The study is primarily focussed on the impact of human activities such as dam constructions. The wet and dry periods are excluded as they are impacted by climate variability. Results of the study confirmed that the impact of the Nagarjuna Sagar on the Krishna River Basin is the highest among the five dams studied, with an average FH score of 0.54 and that of PD Jurala dam is the lowest, with an average FH score of 0.65. This study will be beneficial to help restore regional water resources and eco-environmental system in the middle and lower Krishna River Basin.
... (Figure 7d). The rapid proliferation of such structures has caused the wide spread conversion and fragmentation of wetland habitats and a diminution of ecological flows [42,43]. Fifth, groundwater recession was a serious problem in all three provinces because of the over exploration (Figure 7e-f Effects of natural factors: previous studies have shown that precipitation and temperature determine wetland plant physiology [44], and changes in these parameters, especially temperature Effects of natural factors: previous studies have shown that precipitation and temperature determine wetland plant physiology [44], and changes in these parameters, especially temperature [45], would result in changes in wetland hydrology [46]. ...
Wetlands are the most threatened ecosystem in China, and wetland conservation is a national priority because of their importance for water security, flood mitigation, and biodiversity conservation. A goal has been established for the Beijing-Tianjin-Hebei Region (BTH) to recover 340 km2 of wetlands by 2020. To guide restoration and protection efforts, policymakers need information on the trends of wetland loss, conversion of wetlands, and their associated human drivers. The main drivers of changes in different wetland types in the BTH were identified and quantified from 2000 to 2015. In 2015, there was 6264.07 km2 less wetland area than in 2000, with the remaining wetlands primarily located in Hebei and Tianjin. Reservoirs/ponds were the most abundant wetland type, followed by herbaceous swamps, rivers, canals and channels, and then lakes as the least represented. There were continuous losses of wetlands from 2000 to 2015, with marked decreases for rivers (30.48%), channels/canals (23.30%), and herbaceous swamps (16.12%). However, there was an increase in the area of lakes and reservoirs/ponds, with increases of 54.96% and 3.47%, respectively. The largest changes in natural wetlands were due to agricultural production followed by artificialization and grassland expansion. The driving forces of the observed changes were specific to each local region. According to an aggregated boosted trees (ABT) analysis, gross farm production, total aquatic products, and irrigated area were the top three drivers of the decrease in natural wetlands, which agreed with the main patterns of change in the BTH. The purpose of this study was to provide guidance for policy makers working to meet the 2020 BTH wetland recovery target. Recommendations were provided at the provincial level, including water transfers across provincial boundaries, the control of agricultural expansion, exploration of species-specific irrigation deficits, a reduction in the artificialization of land surfaces, the development of a sustainable intensified aquaculture model, and the promotion of awareness of wetland importance among local people.
... In the paper, the number of classes was determined based on the analysis of geometry of the dendrogram and the plot of the linkage distance curve. The presented methods are commonly used in hydrometeorological research [51][52][53][54][55][56][57][58][59][60]. The mathematical-statistical processing of the analysis results employed statistical procedures included in the Excel (Microsoft) and Statistica 13 (TIBCO Software Inc.) software. ...
The paper identifies relationships between lake water levels and indices of macroscale atmospheric circulations: Arctic Oscillation (AO), North Atlantic Oscillation (NAO), East Atlantic (EA), and Scandinavian pattern (SCAND). Correlation coefficients between synchronous and asynchronous series of monthly water levels and 4 circulation indices were calculated. Based on Ward hierarchical grouping considering 156 correlation coefficients, the groups of lakes were designated due to the strength and term of relation of circulation indices with lake water levels. It was found that these links are not strong but noticeable. The strength of relationships varies in space and time, and the designated groups of lakes refer not only to the climatic diversity of the studied area, but also to some extent to the types of water levels regime. The observed relationships are the most important in the case of AO and NAO (particularly in winter period), and slightly weaker for EA and SCAND. The analysis used mean monthly water levels of 15 lakes in northern Poland from 1976-2015.
Predicting flood event classes aids in the comprehensive investigation of flood behavior dynamics and supports flood early warning and emergency plan development. Existing studies have mainly focused on historical flood event classification and the prediction of flood hydrographs or certain metrics (e.g., magnitude and timing) but have not focused on predicting flood event classes. Our study proposes a new approach for predicting flood event classes based on the class membership functions of flood regime metrics and hydrological modeling. The approach is validated using 1446 unimpacted flood events in 68 headstream catchments widely distributed across China. The new approach performs well, with class hit rates of 68.3% ± 0.4% for all events; 65.8% ± 0.6%, 56.8% ± 0.9%, and 69.5% ± 0.9% for the small, moderate and high spike flood event classes, respectively; and 82.5% ± 1.2% and 75.4% ± 1.1% for the moderate and high dumpy flood event classes, respectively. Furthermore, it performs better in the basins of northern China than in those of southern China, particularly for the small spike flood event class in the Songliao and Yellow River Basins, with hit rates of 80.0% ± 3.2% and 78.8% ± 3.2%, respectively. Our results indicate that the new approach will help improve the prediction performance of flood events and their corresponding classes, and provide deep insights into the comprehensive dynamic patterns of flood events for early warning and control management.
After the completion of the Three Gorges Reservoir (TGR), there was a significant and drastic transformation of the original river habitat. These changes led to the loss of the original fish habitat and the emergence of a new habitat. To effectively classify and assess fish-spawning habitats in the TGR, a novel coastal complexity index (CCI) was developed. The CCI was formulated utilizing satellite remote sensing data and considering the river coastal line and river centerline on the river-reach scale. By integrating the CCI with river morphology, five river habitats were identified: the backwater bay, point bar, straight river channel, convex-bank point bar, and concave-bank deep pool. In order to evaluate the suitability of these habitats for sticky-egg-spawning fish, a single-factor habitat suitability curve was constructed using three key habitat factors: the CCI, slope, and vegetation coverage. This process involved the employment of two distinct methods: the habitat utilization method and the habitat preference method. The former only considered the survey data of spawning grounds, while the latter integrated the overall distribution of habitats in the TGR. Subsequently, a habitat suitability index (HSI) was established to assess the overall suitability of the identified habitats for sticky-egg-spawning fish. The results demonstrated a high classification accuracy, with the backwater bay representing the most prevalent habitat type, accounting for 43.31% of the total habitat types. When considering slope and vegetation coverage, the optimal ranges obtained through the two habitat suitability analysis methods were similar. However, for the CCI, there were variations in the optimal ranges obtained using the two methods. The habitat utilization method indicated an optimal interval of 2–4, while the habitat preference method provided an optimal interval of 4–8. Nonetheless, the assessment results for the spawning habitats’ suitability using both methods yielded essentially identical outcomes. Specifically, the backwater bay, convex-bank point bar, and concave-bank deep pool habitats exhibited higher suitability for spawning than point bar and straight river channel habitats. Further analysis revealed that approximately 75% of the 230 identified backwater bays were categorized as high-quality or higher-quality spawning habitats. In the time since this research was conducted, its findings have served as a theoretical foundation for the protection of aquatic biological resources and habitats.
Ecological flow early warning is crucial for the rational management of watershed water resources. However, determining of accurate ecological flow threshold and choosing the appropriate forecasting model are challenging tasks. In this study, we initially developed a baseflow separation and Tennant method-based technique for calculating ecological river flow. Then an ecological flow early warning model was created using the machine learning technique based on distributed gradient enhancement framework (LightGBM). Finally, we utilized the framework of Shapley Additive Planning (SHAP) to explain how various hydrometeorological factors affect the variations in ecological flow conditions. The Jiaojiang River basin in southeast China is selected as the study area, and the hydrological stations in upstream of Baizhiao (BZA) and Shaduan (SD) are chosen for key analysis. The results of these applications show that the monthly baseflow frequency of the river ecological flow conditions of the two stations in the dry season is 20 % (7.49 m3/s) and 30 % (4.79 m3/s), respectively. The ecological flow level early warning forecasting accuracy is close to 90 % in the BZA and SD stations during dry and wet seasons. The variations of ecological flow are most affected by evaporation and base flow index. The results of this study can serve as a strong basis for the effective allocation and utilization of locally available water resources.
Dams have contributed to population growth and technological innovation by reducing the risk of flooding and allowing humans to cultivate productive alluvial soils on river floodplains. However, in countries where many dams have already been constructed, many problems have been observed, such as river environment degradation, aging of the embankments, and inadequate dam performance. As the social and natural environment surrounding dams is becoming more complex and diverse, it is necessary to understand the current overall status of dams and the history of their construction such that we may consider how social capital and dams are related to human society and the natural environment. In this study, the relationship of basic information of dams and the social background in which the dams exist was examined for Japan, where dam construction began in earnest in the late 1800s and became a driving force for economic development. The situations surrounding dams are drastically changing, as maintenance and management costs increase due to the aging of dams and water demand varies due to changes in the industrial structure of a region. Simultaneously, there are instances where dams are expected to reduce damage, such as in the presence of more severe and frequent droughts and floods caused by climate change. It is therefore necessary to remove or restructure dams while considering numerous complex and diverse factors, such as the local social conditions, potential future changes, and environmental impact of rivers.
For mitigating human-induced river alterations and reviving the dying rivers to preserve natural ecosystem services, the assessment of environmental flow (e-flow) is essential. However, e-flow estimation under data-scarce conditions for the rivers being heavily regulated has become a major issue worldwide under changing environmental conditions, particularly in developing countries. To address this challenge, this study was carried out for estimating time-varying e-flows for a heavily regulated river of Eastern India under data-scarce conditions. In the absence of any pre-impact streamflow data and tributary inflow to the main river reach, this study proposes a framework integrating three methods to estimate e-flow for river reaches. A hydrologic model (first method) was employed to estimate tributary inflows to the main river, which was used in the mass-balance based naturalization approach (second method) for reconstructing the daily long-term natural streamflow from the observed post-impact streamflows at two gauging stations on the main river. Thereafter, the naturalized streamflow was used for estimating e-flows by the GA optimization technique (third method) for two pragmatic scenarios (‘Low Hydrologic Alteration’, and ‘Moderate Hydrologic Alteration’) at the two stations. Analysis of the results revealed that the major impounding and diversion infrastructures built on the river have caused profound alteration to the river reach having an overall degree of hydrologic alteration index greater than 70. The mean post-impact streamflows tend to vary less and have decreased by 35-50% with 2-3 times reduction in the peak flow as compared to the pre-impact condition. The estimated monthly e-flows for the river basin range from 1.2 to 185 m³/s (50-60% of the natural flow) and 0.5 to 80 m³/s (22 to 30% of the natural flow) for the ‘Low’ and ‘Moderate’ alteration scenarios, respectively. Results of this study can aid in formulating efficient strategies for sustainable water resources management in the river basin.
The changes in catchments can be analyzed through the generation of DEM, which is important as input data in hydrologic modeling. This study aims to analyze the effect of anthropogenic activities on hydrological studies based on DEM comparison and GIUH hydrographs. The four DEM datasets (SRTM, ALOS, Copernicus, Sentinel-1) were compared to the topographic map of Makkah City and GPS data in order to assess the quality of the DEM elevation. The GIS Arc Hydro toolbox was used to extract morphometric and Horton–Strahler ratio characteristics to generate a GIUH hydrograph of the catchments of Wadi Nouman and Wadi Ibrahim inside Makkah City. Based on the DEM comparison, Copernicus and SRTM have the highest accuracy, with R2 = 0.9788 and 0.9765, and the lowest RMSE, 3.89 m and 4.23 m, respectively. ALOS and Sentinel-1 have the lowest R2, 0.9687 and 0.9028, and the highest RMSE, 4.27 m and 6.31 m, respectively. GIUH Copernicus DEM on Wadi Nouman has a higher qp and lower tp (0.21 1/h and 2.66 h) than SRTM (0.20 1/h and 2.75 h), respectively. On Wadi Ibrahim, the SRTM has a greater qp and lower tp than Copernicus due to the wadi having two shapes. Based on the anthropogenic effect, the stream network in the mountain area is quite similar for SRTM and Copernicus due to the dominant influence of the mountainous relief and relatively inconsequential influence of anthropogenic activities and DEM noise. In the urban area, the variation of the stream network is high due to differing DEM noise and significant anthropogenic activities such as urban redevelopment. The Copernicus DEM has the best performance of the others, with high accuracy, less RMSE, and stream flow direction following the recent condition.
Excess fluoride (F-) in groundwater can be hazardous to human health. A total of 360 ground water samples was collected from northern Anhui, China, to study the levels, distribution, and source of F-. And on this basis, predicting the spatial distribution of F- in a wider scale space. The range of F- was 0.1-5.8 mg/L, with a mean value of 1.2 mg/L, and 26.4 % of the samples exceeded the acceptable level of 1.5 mg/L. Moreover, the water-rock interaction (fluorite dissolution) and cation alternate adsorption were considered to be two main driving factors of high F- in groundwater. To further illustrate the spatial effects, the BME-RF model was established by combining the main environmental factors. The spatial distribution of F- was quantitatively predicted, and the response to environmental variables was analyzed. The R2 of BME-RF model reached 0.93, the prediction results showed that the region with 1.0-1.5 mg/L of F- accounts for 47.2 % of the total area. The predicted F- content of nearly 70 % of groundwater in this area has exceeded 1.0 mg/L, which was dominated by Na+ and HCO3- type. The spatial variability of F- in the study area was mainly affected by hydrogeological conditions, and the vertical distribution characteristics were related to the spatial variation of slope, distance from runoff, and hydrochemical types. The results of the study provide new insights into the F- concentration prediction in underground environment, especially in the borehole gap area.
The regulation and spatial differences of urban runoffs are of great concern in contemporary hydrological research. However, owing to a shortage of basic data sources and restrictions on urban hydrological simulation functions, simulating and investigating the regulation mechanism behind rainfall-runoff processes remain significantly challenging. In this study, the Time Variant Gain Model (TVGM), a hydrological nonlinear system model, was extrapolated to the hydrodynamic model of an urban drainage network system by integrating it with the widely used Stormwater Management Model (SWMM) to adequately simulate urban runoff events while considering various underlying surfaces and runoff routing modes, such as surface, drainage network and river runoff, in urban regions (i.e., TVGM-SWMM). Moreover, runoff events were characterized using the following four runoff regime metrics: runoff coefficient, capture ratio of annual runoff volume, standardized flood timescale, and the ratio of occurrence time differences between flow and rainfall peak to event duration (peak flow delay time). The characteristics and spatial differences of urban runoff regulations were investigated, and the key impact factors and their relative contributions were identified using multivariate statistical analyses. Four communities were selected as our study areas, consisting of communities from Beijing, Shenzhen, Wuhan, and Chongqing. Our results showed that the TVGM-SWMM performed considerably better than SWMM alone. The comprehensive simulation accuracy of 60% of the events (12/20) improved by 486%, with the bias improving the most, followed by the efficiency coefficient. Barring the runoff coefficient, significant spatial differences were identified at the patch scale for the runoff regime metrics, with differences of 0.43, 0.22, and 0.16 (p<0.05). The key impact factors were the pipe length (r=0.51) in the drainage network system and the forest area ratios (r=0.56), sponge measures (r=0.52), grassland (r=0.48), and impervious surface (r=0.46) in the underlying surfaces. The contributions of the drainage network system and the underlying surfaces were 4.27% and 37.83%, respectively. Regulation in the Beijing community, dominated by grassland regulation, delayed and reduced the peak flow and total runoff volume. In the Shenzhen community, sharp and thin runoff events were mainly generated by impervious surfaces and were not adequately regulated. Forest regulation was the dominant regulation type in the Wuhan community, which reduced the total runoff volume and delayed the peak flow. Waterbody regulation was the primary regulation type in the Chongqing community, which reduced the total runoff volume and peak flow. This study aims to introduce a comprehensive theoretical and technical assessment of the hydrological effects of urbanization and the performance of sponge city construction and provide a reference for urban hydrological model improvements in China.
The aquatic ecological health status was focused on the Huai River Basin (HRB) from the aspects of water quantity, water quality, water ecology, river connectivity, and riparian habitat environment. Ten monitoring sections were set up in the middle and upper reaches of HRB, and 5 experiments of each section were conducted in July and December from 2012 to 2014. Thus, relevant data on the species, the density of phytoplankton, zooplankton and benthic animals, the concentration of water physicochemical variables, and riparian habitat quality were obtained. Eleven key impact factors were chosen using frequency statistics, theoretical analysis, and correlation analysis methods, forming the evaluation index system of aquatic ecological health. Then, the indicator weight value was determined by the combined weight method, and the health degree was evaluated by the comprehensive index method. On the whole, the aquatic ecological health degree of the upper sections (D1 ~ D3) of the Shaying River ranges from 0.334 to 0.927, which is generally in a “sub-healthy” state. The aquatic ecological health degree of the main section of the Huai River (D8 ~ D10) ranges from 0.362 to 0.777, which is in the “critical” or “sub-healthy” state. The Huaidian Sluice (D5) and Fuyang Sluice (D6) in the middle and lower reaches of the Shaying River had the worst aquatic ecological health. Its water ecological health range is 0.283–0.523, and most of them are under “sub-pathologic.” The research results have important theoretical and practical significance. They can enrich the evaluation theories and methods of river aquatic ecological health, help to grasp the aquatic ecological health status in HRB, and provide basic support for aquatic ecological protection and water pollution control in sluice-controlled rivers.
The local water regime of the small-scale Geisel catchment in Central Germany is vastly impacted by strong lignite-mining activities. Missing knowledge about hydrological regimes and low-flow discharges in this impacted region prevented integrated environmental flow assessments. As a consequence, targeted environmental flows of the lower Geisel usually cannot be achieved. To close this knowledge gap, we present a novel approach for an integrated environmental flow assessment in non-natural catchments using long-term baseflow rates, seen as an approach to environmental flows, and simple hydrological methods. Since baseflow rates cannot be estimated accurately in non-natural catchments, we combine 14 different hydrograph separation methods, statistical regionalization, and numerical catchment descriptors. The long-term baseflow equals 0.28 m³/s from 1981 to 2017 (75.4% of total discharge), and in the post-mining era since 2011, the mean baseflow equals 0.115m³/s (77.2% of total discharge). The combination of hydrograph separation with hydrological regionalization and numerical catchment descriptors reveals new opportunities for describing discharge components in non-natural catchments. Determined environmental flows are similar as achieved by other hydrological methods and can be linked to different intensities of anthropogenic impacts. The environmental flow assessment reveals required additional water amounts of 0.0608 m³/s during summer and 0.0874m³/s during winter for achieving quasi-natural flow regime conditions. The approaches enable long-term low-flow analyses and environmental flow assessments in mining impacted catchments.
Mountains and mountain rivers provide a multitude of invaluable goods and services to a profound portion of the planet’s population. As “water towers” of the Earth mountains are sources of the mightiest world rivers and play a pivotal role for global biodiversity, freshwater, and sediment supply. Distinct morphological, climatic, hydrological, hydrochemical, and biological features of mountainous river ecosystems, compared to lowland ones, make them particularly fragile and vulnerable to human interference. Despite a number of remote mountain areas and rivers still remaining intact from direct human pressures, the majority of mountain ecosystems, are being increasingly threatened by adverse local and global changes driven by market economy. To efficiently conserve and sustainably use mountain ecosystems and contribute to the survival of the planet, it is critical to change our standards and life attitudes by realizing and appreciating our immediate connection to the global ecosystem, change attitudes and current consumption patterns, and stimulate the ways our global society functions and interacts with the natural environment.
The modification of sediment and flow regimes caused by damming and river regulation has deleterious effects on the ecological and morphological river processes. This alteration of river systems triggered the implementation of safeguarding environmental flows (e-flows) defined as “the quantity, timing, and quality of water flows required to sustain freshwater and estuarine ecosystems and the human livelihoods and wellbeing that depend on these ecosystems”. In the last decades, physical habitat simulation approaches emerged as fundamental stand-alone or supplementary methods for e-flow assessment. These approaches combine three main components: (1) hydraulic simulation, (2) habitat suitability modeling, to determine the quality of the available habitat, and (3) hydrological analyses (under current and climate change scenarios). E-flow regimes are finally defined, by assessing the spatial and temporal habitat variability for the target taxa or community, after combining these three components. During the process of physical habitat simulation some river processes, such as sediment transport and morphological changes, are often neglected while uncertainties arise from every component. We reviewed the elements that should be considered in every component of the physical habitat simulation to reduce uncertainties with emphasis on the actual trends on the topic and how sediment transport and river morphodynamics can be included within this methodological framework.
In all available methodologies for the assessment of the environmental flow requirements, a sufficient knowledge of the natural hydrological regime is essential. In this chapter the hydrological data that are required in environmental flow assessment studies, their main characteristics, and their importance as well as the specific challenges in the case of mountainous areas are analyzed. The various available data sources, the measurement and processing of hydrological data, and the utilization of modeling techniques for the estimation of streamflow data in the case of ungauged or poorly gauged watersheds and for the naturalization of streamflow data are also presented. A short description of hydrological data series analysis for the determination of environmental water requirements is provided as well. Finally, sources for further reading are provided in each section.
Wetland degradation and loss of wetland is one of the emerging challenges against sustaining such worthy environmental capital having plenty of goods and services. In Barind tract of India and Bangladesh, such trend of wetland conversion is highly explicit. Present paper attempted to capture such trend of wetland loss, conversion of wetland and their associated reasons behind. At present total wetlands area of the basin is 220.9 km2 and which is 35.78% lower than pre-dam wetland coverage. Flow modification triggered by Komardanga dam (34.35% for average flow and 52.24% for peak stream flow have declined) is emerged as one the major reasons behind wetlands loss. It also causes reduction of active flood prone area by 39.72% as well as inconsistent water service to wetlands. De-linking of Punarbhaba river system from Tista river system is another historical cause behind lowering of flow and flood magnitude in Punarbhaba. Loss of tie channels is also responsible for irregular water service to the wetlands. In last 30 years, about 100 km2 of wetland is transformed into agricultural land, which points out the responsibility of agricultural extension for wetland deterioration. So, periodic monitoring of wetlands, release of ecological flow and stop agricultural encroachment are necessary for sustaining wetland.
Freshwater ecosystems are poorly represented in global networks of protected areas. This situation underscores an urgent need for the creation, application, and expansion of durable (long-term and enforceable) protection mechanisms for free-flowing rivers that go beyond conventional protected area planning. To address this need, we must first understand where and what types of protections exist that explicitly maintain the free-flowing integrity of rivers, as well as the efficacy of such policy types. Through policy analysis and an in-depth literature review, our study identifies three main policy mechanisms used for such protections: (1) River Conservation Systems; (2) Executive Decrees and Laws; and (3) Rights of Rivers. We found that globally only eight counties have national river conservation systems while seven countries have used executive decrees and similar policies to halt dam construction, and Rights of Rivers movements are quickly growing in importance, relative to other protection types. Despite the current extent of protection policies being insufficient to tackle the freshwater and biodiversity crises facing the world’s rivers, they do provide useful frameworks to guide the creation and expansion of protections. Ultimately, as countries act on global calls for protections, policy mechanisms must be tailored to their individual social and ecological geographies.
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Water footprint (WF) measures human appropriation of water resources for consumptive use of surface and ground water (blue WF) and soil water (green WF) and for assimilating polluted water (grey WF). Questions have been often asked about the exact meaning behind the numbers from WF accounting. However, to date environmental sustainability of WF has never been assessed at the sub-national level over time. This study evaluated the environmental sustainability of blue, green and grey WF for China's 31 mainland provinces in 2002, 2007 and 2012, and identified the unsustainable hotspots. Overall, the total WF increased by 30% between 2002 and 2012. The growth can be attributed to the increase of grey WF because the green and blue WF showed only a slight rise. Among all provinces investigated in 2012, eleven showed unsustainable blue WF (sustainability index SI<0), which were mainly located in the North China Plain. There were 12 provinces that displayed unsustainable green WF, and they were distributed in China's southern and southeastern areas. The grey WF was not sustainable in approximately two third of provinces (19), which were mainly located in China's middle and northern regions and Guangdong province. More than half of China's provinces showed trends of improved SI of green and blue WF from 2002 to 2012. However, the SI of grey WF decreased in almost two third of provinces. Poor levels of WF sustainability were due to water scarcity and pollution, which intensify the degradation of local rivers and ecosystems and make restoration more difficult. The results shed light on the policy making needed to improve sustainable water management, and ecological restoration of hotspot regions.
The water requirements of rivers are the main focus of this article, which traces the history of environmental flow assessment methods, the emergence of holistic ecosystem level environmental flow frameworks, the details of three of these (DRIFT, ELOHA, FERGRA), and the diversification and expanding scales and scope of their applications. The chapter continues with a discussion of emerging issues for the future of environmental flows under shifting climatic and other environmental regimes, when historical hydrological and ecological baselines will change and new perspectives on environmental water will be needed. The article ends with an outline of efforts to increase the visibility and social-ecological relevance of environmental flows. It presents the Brisbane Declaration and Global Action Agenda on Environmental Flows (2018) and examples of its uptake in global spheres of influence, such as inclusion of environmental flows in the SDG Water Stress Indicator, and the potential for environmental flows to contribute to the Post-2020 Global Biodiversity Framework.
Water footprint (WF) measures human appropriation of global water resources in volumes of consumptive use of surface and ground water (blue WF) and soil water (green WF), and of water required for assimilating the polluted water (grey WF). Questions have been often asked regarding the exact meaning behind the numbers from WF accounting. However, so far environmental sustainability of WF has never been assessed at the sub-national level over time. This study evaluated the environmental sustainability of blue, green and grey WF for 31 provinces in mainland China in 2002, 2007, and 2012, and identified the hotspots of unsustainable regions. Overall, the total WF increased by 30% from 2002 to 2012. The growth was mainly attributed to the increase of grey WF, while green and blue WF only showed a slight rise. Among all provinces investigated in 2012, 11 of them showed unsustainable blue WF (sustainability index SI<0), which were mainly located in the North China Plain. There were 12 provinces that displayed unsustainable green WF, which were distributed in the southern and southeastern parts of China. Besides, the grey WF was not sustainable in about two third of provinces (19), which were mainly located in the middle and northern regions of China, and Guangdong province. More than half provinces showed good trends of improved SI of green and blue WF from 2002 to 2012. However, SI of grey WF decreased in almost two third of provinces. The unsustainability of WF was a key driver for various environmental issues e.g. the water scarcity and water pollution, which could intensify the degradation of local rivers and ecosystems, and make the restoration much more challenging. The results could shed lights on the policy making regarding sustainable water resources management, and the effective ecological restoration in hotspot regions.
Over the last few decades as hydrologists have slowly raised their line of sight above the watershed boundary, it has become increasingly recognised that what happens in the atmosphere, as a major source of moisture for the terrestrial branch of the hydrological cycle, can strongly influence river dynamics at a range of spatial and temporal scales. Notwithstanding this, there is still a tendency for some in the river research community to restrict their gaze to the river channel or floodplain. However, Geoff Petts, the person to which this special issue is dedicated, understood well and widely encouraged a holistic view of river catchment processes. This included an acknowledgment of the role of climate, in its broadest sense, in shaping what happens within and without the river channel. The purpose of this paper therefore is to offer a broad overview of the role of some aspects of climate science in advancing knowledge in river research. Topics to be addressed include the role of climate in influencing river flow regimes, a consideration of the large‐scale climate mechanisms that drive hydrological variability within river basins at interannual to decadal timescales and atmospheric rivers and their link to surface hydrology. In reviewing these topics, a number of key knowledge gaps have emerged including attributing the causes of river flow regime changes to any one particular cause, the nonstationary and asymmetric forcing of river regimes by modes of climate variability and establishing links between atmospheric rivers, and terrestrial river channel processes, fluvial habitats, and ecological change.
Accounting for natural differences in flow variability among rivers, and understanding the importance of this for the protection of freshwater biodiversity and maintenance of goods and services that rivers provide, is a great challenge for water managers and scientists. Nevertheless, despite considerable progress in understanding how flow variability sustains river ecosystems, there is a growing temptation to ignore natural system complexity in favor of simplistic, static, environmental flow ''rules'' to resolve pressing river management issues. We argue that such approaches are misguided and will ultimately contribute to further degradation of river ecosystems. In the absence of detailed empirical information of environmental flow requirements for rivers, we propose a generic approach that incorporates essential aspects of natural flow variability shared across particular classes of rivers that can be validated with empirical biological data and other information in a calibration process. We argue that this approach can bridge the gap between simple hydrological ''rules of thumb'' and more comprehensive environmental flow assessments and experimental flow restoration projects.
Classification and regression trees are ideally suited for the analysis of complex ecological data. For such data, we require flexible and robust analytical methods, which can deal with nonlinear relationships, high-order interactions, and missing values. Despite such difficulties, the methods should be simple to understand and give easily interpretable results. Trees explain variation of a single response variable by repeatedly splitting the data into more homogeneous groups, using combinations of explanatory variables that may be categorical and/or numeric. Each group is characterized by a typical value of the response variable, the number of observations in the group, and the values of the explanatory variables that define it. The tree is represented graphically, and this aids exploration and understanding. Trees can be used for interactive exploration and for description and prediction of patterns and processes. Advantages of trees include: (1) the flexibility to handle a broad range of response types, including numeric, categorical, ratings, and survival data; (2) invariance to monotonic transformations of the explanatory variables; (3) ease and robustness of construction; (4) case of interpretation; and (5) the ability to handle missing values in both response and explanatory variables. Thus, trees complement or represent an alternative to many traditional statistical techniques, including multiple regression, analysis of variance, logistic regression, log-linear models, linear discriminant analysis, and survival models. We use classification and regression trees to analyze survey data from the Australian central Great Barrier Reef, comprising abundances of soft coral taxa (Cnidaria: Octocorallia) and physical and spatial environmental information. Regression tree analyses showed that dense aggregations, typically formed by three taxa, were restricted to distinct habitat types, each of which was defined by combinations of 3-4 environmental variables. The habitat definitions were consistent with known experimental findings on the nutrition of these taxa. When used separately, physical and spatial variables were similarly strong predictors of abundances and lost little in comparison with their joint use. The spatial variables are thus effective surrogates for the physical variables in this extensive reef complex, where information on the physical environment is often not available. Finally, we compare the use of regression trees and linear models for the analysis of these data and show how linear models fail to find patterns uncovered by the trees.
umans have long been fasci- nated by the dynamism of free-flowing waters. Yet we have expended great effort to tame i rivers for transportation, water sup- ply, flood control, agriculture, and ; f
Ecological processes in large rivers are controlled by their flow variability.
However, it is difficult to find measures of hydrological variability that
characterize groups of rivers and can also be used to generate hypotheses
about their ecology. Multivariate analyses of the hydrographs of 52 rivers
worldwide revealed distinctive patterns of flow variability that were often
correlated with climate. For example, there were groups of rivers that
corresponded broadly with ‘tropical’ and ‘dryland’
climates. However, some rivers from continental climates occupy both extremes
of this range, illustrating the limitations of simple classification.
Individual rivers and groups of rivers may also have different hydrographic
‘signatures’, and attempts to combine measures of hydrological
variability into indices mask biologically significant information. This paper
identifies 11 relatively independent measures of hydrological variability that
help categorize river types and are each associated with aspects of fish
biology. Ways are suggested by which the Flood Pulse Concept can be expanded
to encompass hydrological variability and accommodate differences among groups
of rivers from different climatic regions. Such recognition of the complex
role of hydrological variability enhances the value of the concept for river
conservation, management and restoration.
This paper presents a first attempt to estimate the volume of water required for the maintenance of freshwater-dependent ecosystems at the global scale. This total environmental water requirement consists of ecologically relevant low-flow and high-flow components and depends upon the objective of environmental water management. Both components are related to river flow variability and estimated by conceptual rules from discharge time series simulated by the global hydrology model. A water stress indicator is further defined, which shows what proportion of the utilizable water in world river basins is currently withdrawn for direct human use and where this use is in conflict with environmental water requirements. The paper presents an estimate of environmental water requirements for 128 major river basins and drainage regions of the world. It is shown that approximately 20 to 50 percent of the mean annual river flow in different basins needs to be allocated to freshwater-dependent ecosystems to maintain them in fair conditions. This is unlikely to be possible in many developing countries in Asia and North Africa, in parts of Australia, North America, and Europe, where current total direct water withdrawals (primarily for irrigation) already tap into the estimated environmental water requirements. Over 1.4 billion people currently live in river basins with high environmental water stress. This number will increase as water withdrawals grow and if environmental water allocations remain beyond the common practice in river basin management. This paper suggests that estimates of environmental water requirements should be the integral part of global water assessments and projections of global food production.
1. Relatively undisturbed streams in continental U.S.A. were classified according to variation in ten ecologically relevant hydrological characteristics. Measures of flow variability and predictability for average conditions, as well as for low- and high-flow extremes, were extracted from long-term (15–58-year) daily streamflow data for 806 streams.
2. Two groups of sites were analysed: all 806 sites and a subset of 420 ‘best’ sites. For each group, cluster analysis identified ten distinctive stream types, seven permanent and three intermittent. The geographical clustering exhibited by the stream types indicated regional differences in climatic and geological features. A bootstrapping technique applied to the permanent stream classes showed the majority of them were statistically robust.
3. The derived classification of U.S. streams based on ecologically relevant hydrological characteristics provides a comprehensive catalogue of small to mid-size streams that, according to ecological theory, may differ in major aspects of their ecological organization. The classification provides a basis for hypothesis generation and affords an objective framework for matching streams for purposes of comparative ecological investigations.
4. A subset of 118 streams from the ten classification groups was selected to determine whether certain hydrological variables often used by ecologists to make cross-system comparisons are sensitive to the temporal coarseness of the hydrological time series used to derive the variables. The three hydrological variables considered were streamflow predictability, streamflow variability and flood timing.
5. Streamflow predictability (using Colwell’s Index) was calculated at daily, weekly, monthly and seasonal time scales. Estimates of predictability showed either no change across time scales, a gradual and consistent increase across time scales, or a maximum value at the monthly time scale. Coefficient of variation of streamflow was calculated at daily, weekly, monthly, seasonal, and annual time steps. Daily values were always greatest for all streams. Some groups showed minimum variability at the monthly scale, others at the seasonal. Timing of daily peak flows could be detected with 50–90% accuracy across stream groups using coarser grain monthly and annual hydrographic data.
6. Inferences about hydrological similarity among streams across broad geographical scales can be sensitive to choice of time scale used in the hydrological characterization.
Long-term discharge records (17-81 yr) of 78 streams from across the continental USA were analyzed. Based on overall flow variability, flood regime patterns and extent of intermittency, 11 summary statistics were derived from the entire record for each stream. Using a nonhierarchical clustering technique, 9 stream types were identified: harsh intermittent, intermittent flashy, intermittent runoff, perennial flashy, perennial runoff, snowmelt, snow + rain, winter rain, and mesic groundwater. Stream groups separated primarily on combined measures of intermittency, flood frequency, flood predictability, and overall flow predictability, and they showed reasonable geographic affiliation. The positions of the streams in a continuous three-dimensional flow space illustrate the wide range of ecologically important hydrologic variability that can constrain ecological and evolutionary processes in streams. -from Authors
Univariate and discriminant analyses were used to identify the catchment characteristics which contributed to flow variability. Climate, as determined by topography, geographic location, and the composition of the regolith (especially water storage capacity and transmissivity characteristics), accounted for a broad regional distribution of groups. Flow variability decreased with catchment size and area of lake and, to a lesser degree, with catchment slope. Relationships were found between flow variability, and morphological and hydraulic characteristics. The longitudinal variability of water depth and velocity increased with flow variability, indicating a more pronounced pool/riffle structure in rivers with high flow variability. Mean water velocity at mean annual low, median, and mean flow was higher in rivers of low flow variability than in rivers of high flow variability. There were strong associations with periphyton communities and trout distribution and abundance and a weak association with benthic invertebrate communities. Water velocity was the most important hydraulic variable. -from Authors
Stream fish assemblage data for 34 sites in Wisconsin and Minnesota were obtained from archived sources and were used in conjunction with long-term hydrological data to test the hypothesis that functional organization of Ash communities is related to hydrological variability. For each of the 106 species present in the data set, six categories of species traits were derived to describe habitat, trophic, morphological, and tolerance characteristics. A hierarchical clustering routine was used to identify two functionally similar groups of assemblages defined in terms of species presence/absence, Hydrological factors describing streamflow variability and predictability, as well as frequency and predictability of high flow and low flow extremes, were derived for each of the 34 sites and employed to explain differences among the functionally defined groups. Canonical discriminant analysis revealed that the hydrological data could clearly separate the two ecologically defined groups of assemblages, which were associated with either hydrologically variable streams (high coefficient of variation of daily flows, moderate frequency of spates) or hydrologically stable streams (high predictability of daily flows, stable baseflow conditions). Discriminant functions based on hydrological information classified the 34 fish assemblages into the correct ecological group with 85% accuracy. Assemblages from hydrologically variable sites had generalized feeding strategies, were associated with silt and general substrata, were characterized by slow-velocity species with headwater affinities, and were tolerant to silt. Proportions of species traits present at the 34 sites were regressed against an index of hydrological stability derived from a principal components analysis to test the hypothesis that functional organization of assemblages varied across a gradient of hydrological stability. Results were complementary with the discriminant analysis. Findings were in general agreement with theoretical predictions that variable habitats should support resource generalists while stable habitats should be characterized by a higher proportion of specialist species. Several species of fish were identified as indicative of the variable-stable hydrological gradient among stream sites, A taxonomic analysis showed strong geographic patterns in species composition of the 34 assemblages. However, zoogeographic constraints did not explain the observed relationship between stream hydrology and functional organization of fish assemblages, The strong hydrological-assemblage relations found in the 34 midwestern sites suggest that hydrological factors are significant environmental variables influencing fish assemblage structure, and that hydrological alterations induced by climate change (or other anthropogenic disturbances) could modify stream fish assemblage structure in this region.
Temporal patterns in fluctuating physical and biological phenomena are of great interest in several fields of biology, primarily because of their importance as evolutionary constraints. To clarify and simplify the wide variety of terms used to describe aspects of temporal pattern, simple measures of predictability, constancy, and contingency are proposed. These are sufficient to describe the general characteristics of periodic phenomena. The measures are based on the mathematics of information theory. Methods for testing the statistical sig- nificance of these measures are given. Predictability, constancy, and contingency can be determined for either qualitative (categorical) or quantitative (discrete or continuous) variables measured over a period of time. Alternative patterns of seasonal flowering and fruiting of tropical trees are given as an example of a qualitative variable; precipitation data are analyzed as an example of a quantitative variable.
The flow regime is recognized as a key factor determining biological and physical processes and characteristics in rivers. Because of this, there is interest in classification and regionalization of rivers in order to delineate patterns in flow regime character at landscape scales. The River Environment Classification (REC) is an a priori mapped classification of rivers. The REC is based on a hierarchical model of ‘controlling factors’, which are assumed to be the dominant causes of variation in physical and biological characteristics of rivers at a variety of spatial scales. The first and second levels of the REC are based on climate and topography and are expected to discriminate rivers according to differences in their flow regimes. Classes are assigned to individual ‘sections’ of the river network based on categorical description of the climate and topography of each section's unique watershed. This paper describes a test of the REC's ability to explain variation in hydrological character of rivers. Flows that were measured continuously at 335 sites distributed throughout New Zealand were summarized by 13 flow variables and were classified using the REC. Principal components analysis was used to show that the REC classes have distinctive flow regime characteristics. We quantified the classification strength (i.e. the extent to which the mean between-class inter-site dissimilarity exceeds the mean within-class inter-site hydrological dissimilarity) of the REC based on the 13 flow variables. The classification strength of the REC was greater than for two existing regionalizations and a classification that is based on climate, but which does not account for the river network. We attribute the increased classification strength of the REC to its explicit consideration of the causes of spatial variation in flow regimes among rivers and its representation of the network spatial structure of rivers. Copyright © 2005 John Wiley & Sons, Ltd.
River flow regimes, controlled by climatic and catchment factors, vary over a wide range of temporal and spatial scales. This hydrological dynamism is important in determining the structure and functioning of riverine ecosystems; however, such hydroecological associations remain poorly quantified. This paper explores and models relationships between a suite of flow regime predictors and macroinvertebrate community metrics from 83 rivers in England and Wales. A two-stage analytical approach was employed: (1) classification of 83 river basins based upon the magnitude and shape (form) of their long-term (1980–1999) average annual regime to group basins with similar flow responses; and (2) examination of relationships between a total of 201 flow regime descriptors identified by previous researchers and macroinvertebrate community metrics for the whole data set and long-term flow regime classes over an 11-year period (1990–2000). The classification method highlighted large-scale patterns in river flow regimes, identifying five magnitude classes and three shape classes. A west-east trend of flow regime magnitude (high-low) and timing (early-late peak) was displayed across the study area, reflecting climatic gradients and basin controls (e.g. lithology). From the suite of hydrological variables, those associated with the magnitude of the flow regime consistently produced the strongest relationships with macroinvertebrate community metrics for all sites and for the long-term regime composite classes. The results indicate that the classification (subdivision) of rivers into flow regime regions potentially offers a means of increasing predictive capacity and, in turn, better management of fluvial hydrosystems. © Crown copyright 2006. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.
Many environmental flow approaches calculate hydrological indicators on an annual or daily basis and do not consider the multiple scales of a rivers' hydrological character. However, hydrologic processes operate within a temporal and spatial dimension, in accordance with multidimensional and hierarchical views of river systems. This study investigates spatial and temporal patterns of the hydrological character of a large river system, and examines the impact of water-resource development on these patterns. Over 300 regime, history and pulse-scale flow variables have been calculated from simulated discharge data representing ‘reference’ and ‘current’ water-resource development scenarios. Multivariate statistical analyses are used to identify measurement nodes with similar hydrological character and to determine the association between different temporal scale flow variables and groups of nodes. Six spatial hydrological zones are identified in the Condamine–Balonne River, Australia. These hydrological zones are found to have become homogenized with water-resource development. Different temporal scales of flow variables are related to the different hydrological zones, and to water-resource development scenarios. Thus, the temporal dimension of hydrological character is embedded within a spatial dimension of river zonation. Both dimensions should be considered in a hierarchical context, and environmental flow restoration targets may need to be set for each dimension of a river system. Copyright © 2003 John Wiley & Sons, Ltd.
River Environment Classification (REC) is a new system for classifying river environments that is based on climate, topography, geology, and land cover factors that control spatial patterns in river ecosystems. REC builds on existing principles for environmental regionalization and introduces three specific additions to the “ecoregion” approach. First, the REC assumes that ecological patterns are dependent on a range of factors and associated landscape scale processes, some of which may show significant variation within an ecoregion. REC arranges the controlling factors in a hierarchy with each level defining the cause of ecological variation at a given characteristic scale. Second, REC assumes that ecological characteristics of rivers are responses to fluvial (i.e., hydrological and hydraulic) processes. Thus, REC uses a network of channels and associated watersheds to classify specific sections of river. When mapped, REC has the form of a linear mosaic in which classes change in the downstream direction as the integrated characteristics of the watershed change, producing longitudinal spatial patterns that are typical of river ecosystems. Third, REC assigns individual river sections to a class independently and objectively according to criteria that result in a geographically independent framework in which classes may show wide geographic dispersion rather than the geographically dependent schemes that result from the ecoregion approach. REC has been developed to provide a multiscale spatial framework for river management and has been used to map the rivers of New Zealand at a 1:50,000 mapping scale.
1. Environmental flows is now a widely accepted term that covers the quantity, timing, duration, frequency and quality of water flows required to sustain freshwater, estuarine and near‐shore ecosystems and the human livelihoods and well‐being that depend on them.
2. The Water Framework Directive (WFD) of the European Union does not use the term environmental flows explicitly, but requires member states to achieve good ecological status (GES) in all waterbodies, which is assessed by reference to aquatic biology. Nevertheless, it is accepted that ecologically appropriate hydrological regimes are necessary to meet this status. Implementing environmental flows will be a key measure for restoring and managing river ecosystems.
3. The WFD explicitly requires stakeholder involvement, but this has been interpreted as largely a dissemination exercise by national government agencies. Stakeholders are no longer involved in negotiation over ecological objectives as these are pre‐set in the WFD. However, stakeholders may be more involved in reviewing standards and agreeing to measures to restore river ecosystems to the status required by the WFD.
4. The U.K. has undertaken two major projects to set environmental standards for water resources (i) to define water abstraction limits that maintain a healthy river ecosystem and (ii) to define ecologically appropriate flow releases from reservoirs.
5. Implementation of environmental flows remains a major issue, but new ideas such as time‐limited licences and licence trading are being tried.
Hydrologic metrics have been used extensively in ecology and hydrology to summarize the characteristics of riverine flow regimes at various temporal scales but there has been limited evaluation of the sources and magnitude of uncertainty involved in their computation. Variation in bias, precision and overall accuracy of these metrics influences the ability to correctly describe flow regimes, detect meaningful differences in hydrologic characteristics through time and space, and define flow-ecological response relationships. Here, we examine the effects of two primary factors—discharge record length and time period of record—on uncertainty in the estimation of 120 separate hydrologic metrics commonly used by researchers to describe ecologically relevant components of the hydrologic regime. Metric bias rapidly decreased and precision and overall accuracy markedly increased with increasing record length, but tended to stabilize >15 years and did not change substantially >30 years. We found a strong positive relationship between the degree of overlap of discharge record and similarity in hydrologic metrics when based on 15- and 30-year discharge periods calculated within a 36-year temporal window (1965–2000), although hydrologic metrics calculated for a given stream gauge tended to vary only within a restricted range through time. Our study provides critical guidance for selecting an appropriate record length and temporal period of record given a degree of metric bias and precision deemed acceptable by a researcher. We conclude that: (1) estimation of hydrologic metrics based on at least 15 years of discharge record is suitable for use in hydrologic analyses that aim to detect important spatial variation in hydrologic characteristics; (2) metric estimation should be based on overlapping discharge records contained within a discrete temporal window (ideally >50% overlap among records); and (3) metric uncertainty varies greatly and should be accounted for in future analyses. Copyright © 2009 John Wiley & Sons, Ltd.
This paper establishes a framework within which a rapid and pragmatic assessment of river ecosystems can be undertaken at a broad, subcontinental scale, highlighting some implications for achieving conservation of river biodiversity in water-limited countries. The status of river ecosystems associated with main rivers in South Africa was assessed based on the extent to which each ecosystem had been altered from its natural condition. This requires consistent data on river integrity for the entire country, which was only available for main rivers; tributaries were thus excluded from the analyses. The state of main river ecosystems in South Africa is dire: 84% of the ecosystems are threatened, with a disturbing 54% critically endangered, 18% endangered, and 12% vulnerable. Protection levels were measured as the proportion of conservation target achieved within protected areas, where the conservation target was set as 20% of the total length of each river ecosystem. Sixteen of the 112 main river ecosystems are moderately to well represented within protected areas; the majority of the ecosystems have very low levels of representation, or are not represented at all within protected areas. Only 50% of rivers within protected areas are intact, but this is a higher proportion compared to rivers outside (28%), providing some of the first quantitative data on the positive role protected areas can play in conserving river ecosystems. This is also the first assessment of river ecosystems in South Africa to apply a similar approach to parallel assessments of terrestrial, marine, and estuarine ecosystems, and it revealed that main river ecosystems are in a critical state, far worse than terrestrial ecosystems. Ecosystem status is likely to differ with the inclusion of tributaries, since options may well exist for conserving critically endangered ecosystems in intact tributaries, which are generally less regulated than main rivers. This study highlights the importance of healthy tributaries for achieving river conservation targets, and the need for managing main rivers as conduits across the landscape to support ecological processes that depend on connectivity. We also highlight the need for a paradigm shift in the way protected areas are designated, as well as the need for integrated river basin management plans to include explicit conservation visions, targets, and strategies to ensure the conservation of freshwater ecosystems and the services they provide.
1. In an effort to develop quantitative relationships between various kinds of flow alteration and ecological responses, we reviewed 165 papers published over the last four decades, with a focus on more recent papers. Our aim was to determine if general relationships could be drawn from disparate case studies in the literature that might inform environmental flows science and management.
2. For all 165 papers we characterised flow alteration in terms of magnitude, frequency, duration, timing and rate of change as reported by the individual studies. Ecological responses were characterised according to taxonomic identity (macroinvertebrates, fish, riparian vegetation) and type of response (abundance, diversity, demographic parameters). A ‘qualitative’ or narrative summary of the reported results strongly corroborated previous, less comprehensive, reviews by documenting strong and variable ecological responses to all types of flow alteration. Of the 165 papers, 152 (92%) reported decreased values for recorded ecological metrics in response to a variety of types of flow alteration, whereas 21 papers (13%) reported increased values.
3. Fifty-five papers had information suitable for quantitative analysis of ecological response to flow alteration. Seventy per cent of these papers reported on alteration in flow magnitude, yielding a total of 65 data points suitable for analysis. The quantitative analysis provided some insight into the relative sensitivities of different ecological groups to alteration in flow magnitudes, but robust statistical relationships were not supported. Macroinvertebrates showed mixed responses to changes in flow magnitude, with abundance and diversity both increasing and decreasing in response to elevated flows and to reduced flows. Fish abundance, diversity and demographic rates consistently declined in response to both elevated and reduced flow magnitude. Riparian vegetation metrics both increased and decreased in response to reduced peak flows, with increases reflecting mostly enhanced non-woody vegetative cover or encroachment into the stream channel.
4. Our analyses do not support the use of the existing global literature to develop general, transferable quantitative relationships between flow alteration and ecological response; however, they do support the inference that flow alteration is associated with ecological change and that the risk of ecological change increases with increasing magnitude of flow alteration.
5. New sampling programs and analyses that target sites across well-defined gradients of flow alteration are needed to quantify ecological response and develop robust and general flow alteration–ecological response relationships. Similarly, the collection of pre- and post-alteration data for new water development programs would significantly add to our basic understanding of ecological responses to flow alteration.
1. The flow regime is a primary determinant of the structure and function of aquatic and riparian ecosystems for streams and rivers. Hydrologic alteration has impaired riverine ecosystems on a global scale, and the pace and intensity of human development greatly exceeds the ability of scientists to assess the effects on a river‐by‐river basis. Current scientific understanding of hydrologic controls on riverine ecosystems and experience gained from individual river studies support development of environmental flow standards at the regional scale.
2. This paper presents a consensus view from a group of international scientists on a new framework for assessing environmental flow needs for many streams and rivers simultaneously to foster development and implementation of environmental flow standards at the regional scale. This framework, the ecological limits of hydrologic alteration (ELOHA), is a synthesis of a number of existing hydrologic techniques and environmental flow methods that are currently being used to various degrees and that can support comprehensive regional flow management. The flexible approach allows scientists, water‐resource managers and stakeholders to analyse and synthesise available scientific information into ecologically based and socially acceptable goals and standards for management of environmental flows.
3. The ELOHA framework includes the synthesis of existing hydrologic and ecological databases from many rivers within a user‐defined region to develop scientifically defensible and empirically testable relationships between flow alteration and ecological responses. These relationships serve as the basis for the societally driven process of developing regional flow standards. This is to be achieved by first using hydrologic modelling to build a ‘hydrologic foundation’ of baseline and current hydrographs for stream and river segments throughout the region. Second, using a set of ecologically relevant flow variables, river segments within the region are classified into a few distinctive flow regime types that are expected to have different ecological characteristics. These river types can be further subclassified according to important geomorphic features that define hydraulic habitat features. Third, the deviation of current‐condition flows from baseline‐condition flow is determined. Fourth, flow alteration–ecological response relationships are developed for each river type, based on a combination of existing hydroecological literature, expert knowledge and field studies across gradients of hydrologic alteration.
4. Scientific uncertainty will exist in the flow alteration–ecological response relationships, in part because of the confounding of hydrologic alteration with other important environmental determinants of river ecosystem condition (e.g. temperature). Application of the ELOHA framework should therefore occur in a consensus context where stakeholders and decision‐makers explicitly evaluate acceptable risk as a balance between the perceived value of the ecological goals, the economic costs involved and the scientific uncertainties in functional relationships between ecological responses and flow alteration.
5. The ELOHA framework also should proceed in an adaptive management context, where collection of monitoring data or targeted field sampling data allows for testing of the proposed flow alteration–ecological response relationships. This empirical validation process allows for a fine‐tuning of environmental flow management targets. The ELOHA framework can be used both to guide basic research in hydroecology and to further implementation of more comprehensive environmental flow management of freshwater sustainability on a global scale.
Over the past 30 years, ecologists have demonstrated the importance of flow and temperature as primary variables in driving running water, riparian and floodplain ecosystems. As it is important to assess the size and timing of discharge variations in relation to those in temperature, a method is proposed that uses multivariate techniques to separately classify annual discharge and temperature regimes according to their ‘shape’ and ‘magnitude’, and which then combines the classifications. This paper: (i) describes a generally applicable method; (ii) tests the method by applying it to riparian systems on four British rivers using a 20-year record (1977–97) of flow and air temperature; (iii) proposes a hydroecological interpretation of the classification; (iv) considers the degree to which the methodology might provide information to support the design of ecologically acceptable flow regimes.
‘Regimes’ are defined for discharge and air temperature using monthly mean data. The results of applying the classification procedure to four British rivers indicates that the ‘typical’ regimes for each of the four catchments are composite features produced by a small number of clearly defined annual types that reflect interannual variability in hydroclimatological conditions. Annual discharge patterns are dominated by three ‘shape’ classes (accounting for 94% of the station years: class A, early (November) peak; class B, intermediate (December–January) peak; and class C, late (March) peak) and one ‘magnitude’ class (70% of the station years fall into class 3, intermediate), with two subordinate ‘magnitude’ classes: low-flow years (18%) and high flow years (12%). For air temperature, annual patterns are classified evenly into three ‘shape’ and four ‘magnitude’ classes. It is argued that this variety of flow–temperature patterns is important for sustaining ecosystem integrity and for establishing benchmark flow regimes and associated frequencies to aid river management. Copyright © 2000 John Wiley & Sons, Ltd.
This book explains the history and politics of dam building worldwide. It describes the many technical, safety and economic problems that afflict the technology, and explores the role played by international banks and aid agencies in promoting it. The author also examines the rapid growth of the international anti-dam movements, and stresses how replacing large dams with less destructive alternatives will depend upon opening up the dam industry's practices to public scrutiny.
Classification helps us create order out of chaos and be usually used as a means of ordering observation and descriptions. The river classification phase occurs during the newly early stages of development of hydroecology. The purposes and approaches of river classification are simply introduced and the mainly four types of classification schemes, i.e. morphological, hydrological, ecological and value-based schemes, are reviewed and commented. The integration and systematization are the trends of the development in the classification schemes, and the special progresses are made by linking the single factors to the multiplex ones, the qualitative analysis to quatitative ones, the structural features to processes ones, the linear rivers to the large-scale hierachical systems and the natural systems to social ones, etc. With the development of the empirically based laws and finally to the theoretical understanding, and the improvement of the multidiscipline cooperation and data availability, the descriptive classification schemes will give way to the predictive ones. The preexistent experiences from other large countries with a great diversity of aquatic ecosystem are beneficial to the nationwide forthcoming watershed restoration and management in China.
River Environment Classification (REC) is a new system for classifying river environments that is based on climate, topography, geology, and land cover factors that control spatial patterns in river ecosystems. REC builds on existing principles for environmental regionalization and introduces three specific additions to the "ecoregion" approach. First, the REC assumes that ecological patterns are dependent on a range of factors and associated landscape scale processes, some of which may show significant variation within an ecoregion. REC arranges the controlling factors in a hierarchy with each level defining the cause of ecological variation at a given characteristic scale. Second, REC assumes that ecological characteristics of rivers are responses to fluvial (i.e., hydrological and hydraulic) processes. Thus, REC uses a network of channels and associated watersheds to classify specific sections of river. When mapped, REC has the form of a linear mosaic in which classes change in the downstream direction as the integrated characteristics of the watershed change, producing longitudinal spatial patterns that are typical of river ecosystems. Third, REC assigns individual river sections to a class independently and objectively according to criteria that result in a geographically independent framework in which classes may show wide geographic dispersion rather than the geographically dependent schemes that result from the ecoregion approach. REC has been developed to provide a multiscale spatial framework for river management and has been used to map the rivers of New Zealand at a 1:50,000 mapping scale.
Over the past 30 years, ecologists have demonstrated the importance of
flow and temperature as primary variables in driving running water,
riparian and floodplain ecosystems. As it is important to assess the
size and timing of discharge variations in relation to those in
temperature, a method is proposed that uses multivariate techniques to
separately classify annual discharge and temperature regimes according
to their shape and magnitude, and which then combines the
classifications. This paper: (i) describes a generally applicable
method; (ii) tests the method by applying it to riparian systems on four
British rivers using a 20-year record (1977-97) of flow and air
temperature; (iii) proposes a hydroecological interpretation of the
classification; (iv) considers the degree to which the methodology might
provide information to support the design of ecologically acceptable
flow regimes.Regimes are defined for discharge and air temperature using
monthly mean data. The results of applying the classification procedure
to four British rivers indicates that the typical regimes for each of
the four catchments are composite features produced by a small number of
clearly defined annual types that reflect interannual variability in
hydroclimatological conditions. Annual discharge patterns are dominated
by three shape classes (accounting for 94% of the station years: class
A, early (November) peak; class B, intermediate (December-January) peak;
and class C, late (March) peak) and one magnitude class (70% of the
station years fall into class 3, intermediate), with two subordinate
magnitude classes: low-flow years (18%) and high flow years (12%). For
air temperature, annual patterns are classified evenly into three shape
and four magnitude classes. It is argued that this variety of
flow-temperature patterns is important for sustaining ecosystem
integrity and for establishing benchmark flow regimes and associated
frequencies to aid river management.
Many studies have used hydrological variables derived from long-term discharge records to describe the flow regime of streams. However, many streams in the wet-dry tropics of Australia have little or no flow data available for such analysis. In this study, an analysis was undertaken to link significant hydrological variables to a selection of basic catchment characteristics. Long-term discharge records from streams within three relatively well-gauged catchments – Daly (Northern Territory), Fitzroy (Western Australia) and Flinders (Queensland) rivers – were analysed to classify streams into flow regime groupings. Hydrological variables based on flow variability, flood regime pattern and intermittency, were derived for the complete record of each stream. Cluster analysis indicated that streams could be classified broadly into (1) perennial, (2) seasonal, (3) dry seasonal, and (4) seasonal-intermittent. The coefficient of variation of total annual flow and mean annual number of zero flow days were the two most significant variables for classifying streams into flow regime groupings. A selection of broad-scale catchment characteristics based on digital elevation, topographical and geological data were derived for each long-term station within the three catchments. Significant relationships were fitted linking the two most influential hydrological variables, coefficient of variation of total annual flow and mean annual number of zero flow days, to these catchment characteristics. Long-term discharge data from test stations within five other catchments of the wet-dry tropics were used to validate the fitted relationships. Using hydrological variables based on catchment characteristics, most of the test stations were classified within the same flow regime group as that based on hydrological variables derived from flow data. This result indicates that the predicted hydrology variables can be used to broadly classify the flow regime of ungauged or data-limited streams within Australia’s wet-dry tropics.
Huai River basin is a unique area in China with highest density of both water projects (dams and floodgates) and population. The construction of dams & floodgates substantially changed the basin's natural hydrological cycle. In this study, the dams & floodgates discharge simulation module of the Soil and Water Assessment Tool (SWAT) was extended to incorporate the dams & floodgates' dispatch rules. This upgraded version of SWAT model was applied to simulate the monthly flow at twenty-three dams & floodgates and four hydrologic stations for 1991 - 2000. Observed flow data from a total of 27 monitoring cross-sections were used to calibrate and validate the distributed hydrologic parameters. The evaluation coefficients (i.e. relative volume error, correlation coefficient, and efficiency coefficient) are used to elevate the modeling performance in the SWAT of Haihe River Basin. In the calibration period, the volume error coefficients at 18 monitoring stations are within
We illustrate the fundamental importance of fluctuations in natural water flows to the long-term sustainability and productivity of riverine ecosystems and their riparian areas. Natural flows are characterized by temporal and spatial heterogeneity in the magnitude, frequency, duration, timing, rate of change, and predictability of discharge. These characteristics, for a specific river or a collection of rivers within a defined region, shape species life histories over evolutionary (millennial) time scales as well as structure the ecological processes and productivity of aquatic and riparian communities. Extreme events – uncommon floods or droughts – are especially important in that they either reset or alter physical and chemical conditions underpinning the long-term development of biotic communities. We present the theoretical rationale for maintaining flow variability to sustain ecological communities and processes, and illustrate the importance of flow variability in two case studies – one from a semi-arid savanna river in South Africa and the other from a temperate rainforest river in North America. We then discuss the scientific challenges of determining the discharge patterns needed for environmental sustainability in a world where rivers, increasingly harnessed for human uses, are experiencing substantially altered flow characteristics relative to their natural states.
ABSTRACT / The flow regime is regarded by many aquatic ecologists to be the key driver of river and floodplain wetland ecosystems. We have focused this literature review around four key principles to highlight the important mechanisms that link hydrology and aquatic biodiversity and to illustrate the consequent impacts of altered flow regimes: Firstly, flow is a major determinant of physical habitat in streams, which in turn is a major determinant of biotic composition; Secondly, aquatic species have evolved life history strategies primarily in direct response to the natural flow regimes; Thirdly, maintenance of natural patterns of longitudinal and lateral connectivity is essential to the viability of populations of many riverine species; Finally, the invasion and success of exotic and introduced species in rivers is facilitated by the alteration of flow regimes. The impacts of flow change are manifest across broad taxonomic groups including riverine plants, invertebrates, and fish. Despite
growing recognition of these relationships, ecologists still struggle to predict and quantify biotic responses to altered flow regimes. One obvious difficulty is the ability to distinguish
the direct effects of modified flow regimes from impacts associated with land-use change that often accompanies water resource development. Currently, evidence about how rivers function in relation to flow regime and the flows that aquatic organisms need exists largely as a series of untested hypotheses. To overcome these problems, aquatic science needs to move quickly into a manipulative or experimental phase, preferably with the aims of restoration and measuring ecosystem response.
Annual, monthly, low and peak flow data were used to classify and ordinate 138 stream gauges in Victoria. Sixteen hydrological variables were used and low-flow and entire-flow regionalizations were derived. The low-flow regionalization was spatially indistinct and therefore unusable, but the entire-flow regionalization produced five distinctive and spatially significant regions. Least-squares relationships were calculated between mean annual runoff, catchment area and coefficient of variation of annual flows, and the 16 variables. Rivers in the dry western districts of Victoria exhibit high variability of annual, monthly and peak flows, and low specific low flows. The converse is true for rivers in the western highlands of Victoria. Stream regionalizations are a useful tool for stream ecologists, and may be used for generating hypotheses, for detecting representative rivers and for producing baseline stream surveys.
Hydrologic regimes play a major role in determining the biotic composition, structure, and function of aquatic, wetland, and riparian ecosystems. However, human land and water uses are substantially altering hydrologic regimes around the world. Improved quantitative evaluations of human-inducedhydrologic changes,are needed,to advance research on the biotic implications of hydrologic alteration, and to support ecosystem,management,and restoration plans. To facilitate such improved,hydrologic evaluations, we propose a method for assessing the degree of hydrologic alteration attributable to human impacts within an ecosystem. This method, referred to as the Indicators of Hydrologic Alteration(IHA), is based upon an analysis of hydrologic data available either from existing measurement,points within an ecosystem (such as at streamgauges or wells) or model-generated data. We use 32 different parameters, organized into five groups, to statisticallycharacterize hydrologic variation within each year. These 32 parameters provide information on some of the most ecologically significant features of surface and ground water regimes influencing aquatic, wetland, and riparian ecosystems. The hydrologic perturbations associated with activities such as dam operations, flow diversion, ground water pumping, or intensive land use conversion are then assessed,by comparing measures,of central tendency and dispersion for each parameter, between user-defined "pre-impact" and "post-impact" time frames, generating 64 different "Indicators of Hydrologic Alteration." The IHA method,is intended to be used conjunctively with other ecosystem,metrics in inventories 2 of ecosystem integrity, in planning ecosystem management activities, and in setting and
Humanity now uses 26 percent of total terrestrial evapotranspiration and 54 percent of runoff that is geographically and temporally
accessible. Increased use of evapotranspiration will confer minimal benefits globally because most land suitable for rain-fed
agriculture is already in production. New dam construction could increase accessible runoff by about 10 percent over the next
30 years, whereas population is projected to increase by more than 45 percent during that period.
1. Human use of land and water resources modifies many streamflow characteristics, which can have significant ecological consequences. Streamflow and invertebrate data collected at 111 sites in the western U.S.A. were analysed to identify streamflow characteristics (magnitude, frequency, duration, timing and variation) that are probably to limit characteristics of benthic invertebrate assemblages (abundance, richness, diversity and evenness, functional feeding groups and individual taxa) and, thus, would be important for freshwater conservation and restoration. Our analysis investigated multiple metrics for each biological and hydrological characteristic, but focuses on 14 invertebrate metrics and 13 streamflow metrics representing the key associations between streamflow and invertebrates.
2. Streamflow is only one of many environmental and biotic factors that influence the characteristics of invertebrate assemblages. Although the central tendency of invertebrate assemblage characteristics may not respond to any one factor across a large region like the western U.S.A., we postulate that streamflow may limit some invertebrates. To assess streamflow characteristics as limiting factors on invertebrate assemblages, we developed a nonparametric screening procedure to identify upper (ceilings) or lower (floors) limits on invertebrate metrics associated with streamflow metrics. Ceilings and floors for selected metrics were then quantified using quantile regression.
3. Invertebrate assemblages had limits associated with all streamflow characteristics that we analysed. Metrics of streamflow variation at daily to inter‐annual scales were among the most common characteristics associated with limits on invertebrate assemblages. Baseflow recession, daily variation and monthly variation, in streamflow were associated with the largest number of invertebrate metrics. Since changes in streamflow variation are often a consequence of hydrologic alteration, they may serve as useful indicators of ecologically significant changes in streamflow and as benchmarks for managing streamflow for ecological objectives.
4. Relative abundance of Plecoptera, richness of non‐insect taxa and relative abundance of intolerant taxa were associated with multiple streamflow metrics. Metrics of sensitive taxa (Ephemeroptera, Plecoptera and Trichoptera), and intolerant taxa generally had ceilings associated with flow metrics while metrics of tolerant taxa, non‐insects, dominance and chironomids generally had floors. Broader characteristics of invertebrate assemblages such as abundance and richness had fewer limits, but these limits were nonetheless associated with a broad range of streamflow characteristics.
This is the first of three related papers that summarizes streamflow character-istics of a set of 1221 global rivers. The rivers are well distributed world-wide, are un-impacted by upstream reservoirs or diversions for the period of data collection and have at least 10 years of continuous monthly and annual streamflow data. The following key features of annual flows are examined: mean, variability and skewness, distribution type (Gamma or Lognormal), flow percentiles and dependence. High and low frequency persis-tence is examined through the Empirical Mode Decomposition technique. Low flow run length, magnitude and severity are also explored, where severity is based on Extended Deficit Analysis. It has been observed elsewhere that there are large differences in hydro-logic characteristics between Australia and southern Africa in contrast to the rest of the world. This issue is tested further in this paper. The range of analyses and results pre-sented herein also form a suite of empirical evidence that future unified theories of hydrology at the catchment scale must be able to adequately describe. ª 2007 Elsevier B.V. All rights reserved.
Recognition of the escalating hydrological alteration of rivers on a global scale and resultant environmental degradation, has led to the establishment of the science of environmental flow assessment whereby the quantity and quality of water required for ecosystem conservation and resource protection are determined.
A global review of the present status of environmental flow methodologies revealed the existence of some 207 individual methodologies, recorded for 44 countries within six world regions. These could be differentiated into hydrological, hydraulic rating, habitat simulation and holistic methodologies, with a further two categories representing combination‐type and other approaches.
Although historically, the United States has been at the forefront of the development and application of methodologies for prescribing environmental flows, using 37% of the global pool of techniques, parallel initiatives in other parts of the world have increasingly provided the impetus for significant advances in the field.
Application of methodologies is typically at two or more levels. (1) Reconnaissance‐level initiatives relying on hydrological methodologies are the largest group (30% of the global total), applied in all world regions. Commonly, a modified Tennant method or arbitrary low flow indices is adopted, but efforts to enhance the ecological relevance and transferability of techniques across different regions and river types are underway. (2) At more comprehensive scales of assessment, two avenues of application of methodologies exist. In developed countries of the northern hemisphere, particularly, the instream flow incremental methodology (IFIM) or other similarly structured approaches are used. As a group, these methodologies are the second most widely applied worldwide, with emphasis on complex, hydrodynamic habitat modelling. The establishment of holistic methodologies as 8% of the global total within a decade, marks an alternative route by which environmental flow assessment has advanced. Such methodologies, several of which are scenario‐based, address the flow requirements of the entire riverine ecosystem, based on explicit links between changes in flow regime and the consequences for the biophysical environment. Recent advancements include the consideration of ecosystem‐dependent livelihoods and a benchmarking process suitable for evaluating alternative water resource developments at basin scale, in relatively poorly known systems. Although centred in Australia and South Africa, holistic methodologies have stimulated considerable interest elsewhere. They may be especially appropriate in developing world regions, where environmental flow research is in its infancy and water allocations for ecosystems must, for the time being at least, be based on scant data, best professional judgement and risk assessment. Copyright © 2003 John Wiley & Sons, Ltd.
is a Pew Fellow in Conservation and the Environment and directs the Global Water Policy Project in Amherst, MA 01002-3440. Her research focuses on international water and sustainability issues. This year marks the 200th anniversary of the publication of Thomas Malthus's famous essay postulating that human population growth would outstrip the earth's food-producing capabilities. His writing sparked a debate that has waxed and waned over the last two centuries but has never disappeared completely. Stated simply, Malthus's proposition was that because population grows exponentially while food supplies expand linearly, the former would eventually outpace the latter. He predicted that hunger, disease, and famine would result, leading to higher death rates. One of the missing pieces in Malthus's analysis was the power of science and technology to boost land productivity and thereby push back the limits imposed by a finite amount of cropland. It was only in the twenti-eth century that scientific research led to marked increases in agricultural productivity. Major advances, such as the large-scale production of nitrogen fertilizers and the breeding of high-yielding wheat and rice varieties, have boosted crop yields and enabled food production to rise along with the world population (Dyson 1996). Between 1950 and 1995, human numbers increased by 122% (US Bureau of the Census 1996), while the area planted in grain expanded by only 17% (USDA 1996, 1997c). It was a 141% increase in grainland productivity, supple-mented with greater fish harvests and larger livestock herds, that allowed food supplies to keep pace with popu-lation and diets for a significant portion of humanity to improve. Despite this remarkable success, concern about future food prospects has risen in recent years because of a marked slowdown in the growth of world grain yields, combined with an anticipated doubling of global food demand between 1995 and 2025 (McCalla 1994, FAO 1996). Whereas annual grain yields (expressed as three-year averages) rose 2–2.5 % per year during every decade since 1950, they registered growth of only 0.7% per year during the first half of the 1990s (Brown 1997, USDA 1997a, 1997b). Excluding the former Soviet Union, where the political breakup and economic reforms led to large drops in productivity, global grain yields in-creased an average of 1.1% per year from 1990 to 1995, approximately one-half the rate of the previous four decades (Brown 1997). Today, the principal difference between those analysts projecting adequate food supplies in 2025 and those anticipating significant shortfalls is the assumed level of productivity growth—specifically, whether annual productivity over the next three decades is likely to grow at closer to the 1% rate of the 1990s or the 2–2.5% rate of the previous four decades. Water—along with climate, soil fertility, the choice of crops grown, and the genetic potential of those crops— is a key determinant of land productivity. Adequate moisture in the root zone of crops is essential to achieving both maximum yield and production stability from season to season. A growing body of evidence suggests that lack of water is already constraining agricultural output in many parts of the world (Postel 1996, UNCSD 1997). Yet to date, I am aware of no global food assessment that systematically addresses how much water will be required to produce the food supplies of 2025 and whether that water will be available where and when it is needed. As a result, the nature and severity of water constraints remain ill defined, which, in turn, is hampering the development of appropriate water and agricultural strategies. In this article, I estimate the volume of water currently consumed in producing the world's food, how much additional water it will take to satisfy new food demands in 2025, and how much of this water will likely need to come from irrigation. I then place this expected irrigation demand in the context of global and regional water availability and trends. Finally, I discuss the policy and investment implications that emerge from the analysis.
Many river restoration projects are focusing on restoring environmental flow regimes to improve ecosystem health in rivers that have been developed for water supply, hydropower generation, flood control, navigation, and other purposes. In efforts to pre-vent future ecological damage, water supply planners in some parts of the world are beginning to address the water needs of river ecosystems proactively by reserving some portion of river flows for ecosystem support. These restorative and protective actions require development of scientifically credible estimates of environmental flow needs. This paper describes an adaptive, inter-disciplinary, science-based process for developing environmental flow recommendations. It has been designed for use in a variety of water management activities, including flow restoration projects, and can be tailored according to available time and resources for determining environmental flow needs. The five-step process includes: (1) an orientation meeting; (2) a literature review and summary of existing knowledge about flow-dependent biota and ecological processes of concern; (3) a workshop to develop ecological objectives and initial flow recommendations, and identify key information gaps; (4) implementation of the flow recommendations on a trial basis to test hypotheses and reduce uncertainties; and (5) monitoring system response and conducting further research as warranted. A range of recommended flows are developed for the low flows in each month, high flow pulses throughout the year, and floods with targeted inter-annual frequencies. We describe an application of this process to the Savannah River, in which the resultant flow recommendations were incorporated into a comprehensive river basin planning process conducted by the Corps of Engineers, and used to initiate the adaptive management of Thurmond Dam.
Freshwater biodiversity is highly endangered and faces increasing threats worldwide. To be complete, regional plans that identify critical areas for conservation must capture representative components of freshwater biodiversity as well as rare and endangered species. We present a spatially hierarchical approach to classify freshwater systems to create a coarse filter to capture representative freshwater biodiversity in regional conservation plans. The classification framework has four levels that we described using abiotic factors within a zoogeographic context and mapped in a geographic information system. Methods to classify and map units are flexible and can be automated where high-quality spatial data exist, or can be manually developed where such data are not available. Products include a spatially comprehensive inventory of mapped and classified units that can be used remotely to characterize regional patterns of aquatic ecosystems. We provide examples of classification procedures in data-rich and data-poor regions from the Columbia River Basin in the Pacific Northwest of North America and the upper Paraguay River in central South America. The approach, which has been applied in North, Central, and South America, provides a relatively rapid and pragmatic way to account for representative freshwater biodiversity at scales appropriate to regional assessments.
Hydrological simulation and assessment in a dam-sluice regulated river basin are a complex and challenging issue. In this article, an improved SWAT2000 modelling system was developed that incorporated the Shuffled complex evolution (SCEUA) optimization algorithm and the multi-site and multi-objective calibration strategy. The implication of multi-objective is different for different types of outlets, i.e. streamflow for an ordinary outlet, inflow for a sluice, and water storage for a reservoir. Model parameters were redefined to improve model simulations. The surface runoff lag time (SURLAG) was extended as a spatially distributed parameter, and a correction coefficient was introduced to modify the saturated hydraulic conductivity. The modelling system was then applied to the Huai River basin of China under various climatic conditions, including a very dry year (1999), a dry year (1981), an average year (1971), and wet year (1991). In all, 26 dams and 35 sluices were considered, among which about 20 dams/sluices were used for model calibration. The impact assessment primarily focused on the very dry year (1999). The results indicated that the released water from large reservoirs was blocked in the river channels by sluices located downstream. In the very dry year, the dam-sluice operations could result in an increase of the runoff volume during the non-flood season and a decrease in runoff during the flood season, but the changing magnitude during the non-flood season was much greater. An important conclusion of this case study is that the sluices in the Sha-Yin branch located in the north region and the dams in the southern mountainous region above the Wangjiaba Hydrological Station have played the most significant role in regulating the streamflow of the entire river basin. The methods addressed in this article can simulate hydrological regime in the river basins regulated by dams and sluices under different climatic conditions at the whole-watershed scale.
River scientists are increasingly asked to provide recommendations about the amount and timing of water flows needed to support ecosystem health. The need for scientifically credible environmental flow assessments and the limited availability of resources to conduct in-depth studies place a premium on methods that can be readily applied at low cost. The Indicators of Hydrologic Alteration (IHA) software program was originally developed by The Nature Conservancy in the 1990s to quickly process daily hydrologic records to enable characterization of natural water conditions and facilitate evaluations of human-induced changes to flow regimes. The evolution of the IHA software is discussed, including recent revisions and additions to the IHA that have improved its utility in environmental flow-setting processes. Drawing from holistic methodologies developed around the world, the ability to calculate characteristics of five components of flow important to river ecosystem health – extreme low flows, low flows, high-flow pulses, small floods and large floods – has been added to the IHA. A practical advantage of these environmental flow components is that an environmental flow prescription based upon them can be readily implemented in most water management settings. Frequently used as a one-time generator of flow statistics, the value of the IHA increases when used interactively with ecological models. A process for linking IHA output to an ecological model to explore flow-ecology relationships within an adaptive management context is presented and demonstrated through its application on the Green River, Washington. The IHA used in conjunction with ecological models facilitates the creation and testing of flow-ecology hypotheses, formulation of water and land protection or restoration goals, and development of a focused research and monitoring program, all important components of environmental flow-setting processes.
Abstract – We developed classification/multiple discriminant analysis models to predict fish assemblage structure and tested whether the predictive power of these models varied with discharge variability. Models developed for assemblages characterized by the density of component species for two rivers with low discharge variability had better predictive power than did models developed for two rivers of higher variability. Similar distinction between rivers of differing flow variability was not evident for models based on assemblages characterized by the presence or absence of component species. Factors such as the within-river level of beta diversity, location of study sites relative to the river mouth and the degree of covariation in species' occurrence appeared important determinants of predictive power in these models. Randomization tests (Mantel tests) were used to determine the degree of association between site by site association matrices generated for fish assemblage structure (both density and presence/absence) and habitat structure (catchment, physical, microhabitat or a combination). This approach revealed that in most cases, catchment-related variables explained almost as much of the variation in assemblage structure as variables related to in-stream habitat structure and that greater association was detected for comparisons based on presence/absence rather than density data. The addition of in-stream habitat variables to catchment-related variables usually resulted in explaining the greatest amount of variation. These data suggest that most of the structure observed in the fish assemblages of the study rivers was a result of the effect of regional or catchment factors in determining which species were present at an individual site and that local factors were then important in determining the abundance of the component species. It is at this level that the effects of regional differences in discharge variability were expressed. Although significantly different from random for all comparisons, Mantel's tests revealed that a substantial amount of variation in the fish assemblage data sets could not be explained by the abiotic (habitat) data sets. It is suggested that the assemblages in question did not represent unit discrete assemblages but were composed of species varying along individual environmental gradients. Predictive models may be better achieved by modelling the distribution and abundance of individual species rather than assemblages.†
To investigate the impacts of urbanization and climatic fluctuations on stream flow magnitude and variability in a Mediterranean climate, the HEC-HMS rainfall/runoff model is used to simulate stream flow for a 14-year period (October 1, 1988, to September 30, 2002) in the Atascadero Creek watershed located along the southern coast of California for 1929, 1998, and 2050 (estimated) land use conditions (8, 38 and 52 percent urban, respectively). The 14-year period experienced a range of climatic conditions caused mainly by El Nino-Southern Oscillation variations. A geographic information system is used to delineate the watershed and parameterize the model, which is calibrated using data from two stream flow and eight rainfall gauges. Urbanization is shown to increase peak discharges and runoff volume while decreasing stream flow variability. In all cases, the annual and 14-year distributions of stream flow are shown to be highly skewed, with the annual maximum 24 hours of discharge accounting for 22 to 52 percent of the annual runoff and the maximum ten days of discharge from an average El Nino year producing 10 to 15 percent of the total 14-year discharge. For the entire period of urbanization (1929 to 2050), the average increase in annual maximum discharges and runoff was 45 m3/s (300 percent) and 15 cm (350 percent), respectively. Additionally, the projected increase in urbanization from 1998 to 2050 is half the increase from 1929 to 1998; however, increases in runoff (22 m3/s and 7 cm) are similar for both scenarios because of the region's spatial development pattern.
Increased understanding of the ecological importance of temporal environmental variation has led to a concern that many regulated rivers lack the natural variations in flow required to maintain pre-regulation communities. Many of the existing environmental flow methods fail to adequately address this concern. This paper presents a new approach to characterizing flow variations for environmental flow studies using knowledge of the influence of flow events on biological and geomorphic processes. This approach has the advantage that ecological benefits of the environmental flow are clearly articulated, available knowledge is included in the development of flow recommendations and the method accounts for the natural dynamism in flow-related ecosystem processes by using the natural flow regime as a template for the environmental flow regime. The Flow Events Method is demonstrated in an application to the Snowy River in southeast Australia. Copyright © 2003 John Wiley & Sons, Ltd.
Hydrologic landscapes are multiples or variations of fundamental hydrologic landscape units. A fundamental hydrologic landscape unit is defined on the basis of land-surface form, geology, and climate. The basic land-surface form of a fundamental hydrologic landscape unit is an upland separated from a lowland by an intervening steeper slope. Fundamental hydrologic landscape units have a complete hydrologic system consisting of surface runoff, ground-water flow, and interaction with atmospheric water. By describing actual landscapes in terms of land-surface slope, hydraulic properties of soils and geologic framework, and the difference between precipitation and evapotranspiration, the hydrologic system of actual landscapes can be conceptualized in a uniform way. This conceptual framework can then be the foundation for design of studies and data networks, syntheses of information on local to national scales, and comparison of process research across small study units in a variety of settings. The Crow Wing River watershed in central Minnesota is used as an example of evaluating stream discharge in the context of hydrologic landscapes. Lake-research watersheds in Wisconsin, Minnesota, North Dakota, and Nebraska are used as an example of using the hydrologic-land-scapes concept to evaluate the effect of ground water on the degree of mineralization and major-ion chemistry of lakes that lie within ground-water flow systems.
A conceptual, continuous time model called SWAT (Soil and Water Assessment Tool) was developed to assist water resource managers in assessing the impact of management on water supplies and nonpoint source pollution in watersheds and large river basins. The model is currently being utilized in several large area projects by EPA, NOAA, NRCS and others to estimate the off-site impacts of climate and management on water use, non-point source loadings, and pesticide contamination. Model development, operation, limitations, and assumptions are discussed and components of the model are described. In Part II, a GIS input/output interface is presented along with model validation on three basins within the Upper Trinity basin in Texas.
Clustering of multivariate data is a commonly used technique in ecology, and many approaches to clustering are available. The results from a clustering algorithm are uncertain, but few clustering approaches explicitly acknowledge this uncertainty. One exception is Bayesian mixture modelling, which treats all results probabilistically, and allows comparison of multiple plausible classifications of the same data set. We used this method, implemented in the AutoClass program, to classify catchments (watersheds) in the Murray Darling Basin (MDB), Australia, based on their physiographic characteristics (e.g. slope, rainfall, lithology). The most likely classification found nine classes of catchments. Members of each class were aggregated geographically within the MDB. Rainfall and slope were the two most important variables that defined classes. The second-most likely classification was very similar to the first, but had one fewer class. Increasing the nominal uncertainty of continuous data resulted in a most likely classification with five classes, which were again aggregated geographically. Membership probabilities suggested that a small number of cases could be members of either of two classes. Such cases were located on the edges of groups of catchments that belonged to one class, with a group belonging to the second-most likely class adjacent. A comparison of the Bayesian approach to a distance-based deterministic method showed that the Bayesian mixture model produced solutions that were more spatially cohesive and intuitively appealing. The probabilistic presentation of results from the Bayesian classification allows richer interpretation, including decisions on how to treat cases that are intermediate between two or more classes, and whether to consider more than one classification. The explicit consideration and presentation of uncertainty makes this approach useful for ecological investigations, where both data and expectations are often highly uncertain.