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Contour plots of the real part (A), the modulus (B), and the global power spectrum (C) of Morlet wavelet transform coefficients.
Source publication
River flooding affects more people worldwide than other natural hazards. Thus, analysis of the changes in flood regime caused by global warming and increasing anthropogenic activities will help us make adaptive plans for future flood management. The nonstationary flood behavior in the upper Yangtze River was examined comprehensively in terms of tre...
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Mitigating global warming and climate change has become a crucial mission for sustainable development all over the world. This research focus on the feasibility of development near-zero water consumption buildings. The water saving motivation is necessary to be raised by a clear measurement basis for the rational water use of buildings and encourag...
Citations
... The area's climate shows a pattern of wet summers and relatively dry winters with an annual mean of 1525 mm in precipitation. This area of China is located in the subtropical monsoon belt and is, as the monsoon can stagnate over the middle reaches of the Yangtze River, one of the most flood-prone regions of China (Fang et al., 2019;Zhang et al., 2021). Therefore, the tributary watershed is suitable for conducting the modeling analysis of the interactions and effects between major parameters of the hydrological model. ...
The coupled development of soil and vegetation leads to a close interaction between their attributes and impacts the sustainability of eco-hydrology at different scales. In this study, a distributed hydrological model of a watershed was created with the Soil and Water Assessment Tool (SWAT) in a representative tributary watershed for investigating such effects. The results quantify the intensity and interval of the relationship and the impacts on hydrological composition between major model parameters. Among the examined interactions, SCS runoff curve number (CN2) and soil bulk density (BD) show the strongest interaction and effects on surface runoff, lateral flow, percolation, groundwater flow, and soil water content. The interaction between CN2 and BD highlights the importance of the soil surface and topsoil for runoff generation processes. In addition, the soil-vegetation interactions show clear seasonal effects due to impacts from the changes in land use and precipitation patterns, which influence the river discharge and flow variability more significantly at the sub-basin scale than at the watershed scale. The insight into the interactions and hydrological effects of soil and vegetation may help improve the spatial planning for ecological sustainability and hydrological extrema mitigation with a more reliable reflection of the spatial heterogeneity.
... Observations indicate that the annual streamflow and flood volume in the UYR is decreasing (Y. Zhang, Fang, et al., 2021). However, the short length of observation records makes it difficult to assess the temporal patterns of these hydrological extremes and identify the associated mechanisms involving natural variability and anthropogenic warming (Chen & Wu, 2014;Wei et al., 2013;Y. ...
... nual streamflow and flood volume in the UYR is decreasing (Y. Zhang, Fang, et al., 2021). However, the short length of observation records makes it difficult to assess the temporal patterns of these hydrological extremes and identify the associated mechanisms involving natural variability and anthropogenic warming (Chen & Wu, 2014;Wei et al., 2013;Y. Zhang, Fang, et al., 2021), especially over decadal and centennial timescales (Fang et al., 2018;Gu et al., 2018;Wu et al., 2021). Therefore, a long-term and high-resolution streamflow record is crucial for improving our understanding of the background and mechanisms associated with extreme hydrological events across the UYR. ...
... The UYR is located in southwest China and lies within the region spanning between 21°8ʹ-34°20ʹN and 97°22ʹ-110°11ʹE (Figure 1a). It has a drainage area of 1.054 million km 2 , which accounts for 59% of the total drainage area of the Yangtze River (Y. Zhang, Fang, et al., 2021). In contrast to the middle and lower reaches of the Yangtze River, the effects of current human activity on the whole of the UYR are minor, and the annual changes in streamflow are influenced mainly by natural factors, rather than hydraulic structures (J. ...
... Besides, both permanent arid climate areas, such as areas in northwest China, and seasonal drought areas are presented in China. Studies have exhibited that the summer monsoon rainfall indicates a declining trend over North China (105 • E− 125 • E, 35 • N− 45 • N) whereas in south China over the Yangtze River valley (105 • E− 125 • E, 25 • N− 35 • N), the monsoon rainfall has shown an increasing trend during recent decades (Gong and Ho, 2002;Preethi et al., 2017;Zhang et al., 2021b). The Huaihe River is located in the north-south climate transition belt in China (Lu and Zhu;Wang et al., 2021a), whose basin borders the shifted temperature distribution were also noted (Almazroui et al., 2021a). ...
Study region
The Huaihe River Basin is located in China’s north-south climate transition belt, where massive droughts occurred in history.
Study focus
To comprehensively capture how climate extremes have behaved in the past, this paper analyzed the trend, change point, and periodicity of drought at multiple spatial-temporal scales based on the Standardized Precipitation Indexes (SPI). And the historical simulation experiments of 9 CMIP6 models were evaluated against observations for further exploring the behavior of climate extremes in future periods.
New hydrological insights for the region
The period of SPI-12 lies around 2–7 years, while the period of SPI-3 is at the time scale of 1–3 years, indicating potential teleconnections with large-scale climate events. Moreover, MIROC6 and CESM2 models exhibited better performance in simulating precipitation than individual models and multi-model ensemble mean. The uncertainties of the model ensemble mean of 3 selected models in depicting droughts have a good consistency with the observations. The projection experiments of CMIP6 derived from the selected historical simulation models can be used to predict drought in the near future and the far future under different scenarios over the Huaihe River Basin.
... Observations indicate that the annual streamflow and flood volume in the UYR is decreasing (Y. Zhang, Fang, et al., 2021). However, the short length of observation records makes it difficult to assess the temporal patterns of these hydrological extremes and identify the associated mechanisms involving natural variability and anthropogenic warming (Chen & Wu, 2014;Wei et al., 2013;Y. ...
... nual streamflow and flood volume in the UYR is decreasing (Y. Zhang, Fang, et al., 2021). However, the short length of observation records makes it difficult to assess the temporal patterns of these hydrological extremes and identify the associated mechanisms involving natural variability and anthropogenic warming (Chen & Wu, 2014;Wei et al., 2013;Y. Zhang, Fang, et al., 2021), especially over decadal and centennial timescales (Fang et al., 2018;Gu et al., 2018;Wu et al., 2021). Therefore, a long-term and high-resolution streamflow record is crucial for improving our understanding of the background and mechanisms associated with extreme hydrological events across the UYR. ...
... The UYR is located in southwest China and lies within the region spanning between 21°8ʹ-34°20ʹN and 97°22ʹ-110°11ʹE (Figure 1a). It has a drainage area of 1.054 million km 2 , which accounts for 59% of the total drainage area of the Yangtze River (Y. Zhang, Fang, et al., 2021). In contrast to the middle and lower reaches of the Yangtze River, the effects of current human activity on the whole of the UYR are minor, and the annual changes in streamflow are influenced mainly by natural factors, rather than hydraulic structures (J. ...
Ongoing global warming has a strong influence on regional hydrological cycles. The upper reaches of the Yangtze River (UYR) are highly vulnerable to extreme hydrological droughts and floods, but a lack of long‐term streamflow observations has limited our understanding on global warming influences. Here, we establish an annually resolved and absolutely dated tree‐ring oxygen (δ¹⁸O) isotope chronology and use it to reconstruct the summer streamflow history of the UYR between 1260 and 2017. The UYR experienced 79 extreme floods and 107 extreme hydrological droughts over this period. We found a trend toward dry conditions in the region with tendencies for an increased drought probability since around 1850s. Especially, the frequency of hydrological droughts in recent decades has been outside the envelope of natural variability of extreme hydrological droughts. The temporal evolution of hydrological extremes is closely linked to variability of the Indian summer monsoon (ISM) at decadal scales. The UYR has experienced more frequent droughts during dry spells and experienced more frequent floods during wet spells of the ISM. The recent increase in the frequency of hydrological droughts is consistent with the observed trend toward a weaker ISM and increasing temperatures. Weaker transport of low‐level moisture and greater evaporation caused by global warming have contributed to the increase in extreme hydrological droughts. Our results thus provide a long‐term context for observed hydrological changes and suggest that the UYR will experience more frequent and severe extreme events as a consequence of increasing greenhouse gas emissions.
... Large dams have transformed large rivers from flowing to static, resulting in variations in water levels and flows far beyond their natural magnitude due to massive evaporation of stored water or its diversion by humans for irrigation or water transfer [142]. On the one hand, dams undermine river connectivity and water stability by reducing seasonal flows, most notably by cutting peak flood flows and storage period flows [143]. For example, the construction of the Xiaolangdi dam mitigated 78% of the potential flooding in the Yellow River basin [144]. ...
Basin ecohydrological processes are essential for informing policymaking and social development in response to growing environmental problems. In this paper, we review watershed ecohydrology, focusing on the interaction between watershed ecological and hydrological processes. Climate change and human activities are the most important factors influencing water quantity and quality, and there is a need to integrate watershed socioeconomic activities into the paradigm of watershed ecohydrological process studies. Then, we propose a new framework for integrated watershed management. It includes (1) data collection: building an integrated observation network; (2) theoretical basis: attribution analysis; (3) integrated modeling: medium- and long-term prediction of ecohydrological processes by human–nature interactions; and (4) policy orientation. The paper was a potential solution to overcome challenges in the context of frequent climate extremes and rapid land-use change.
... Severe floods of Yangtze river. Rainfall distribution is grossly inhomogeneous in both spatial and temporal aspects in the Yangtze River Basin, benefiting from its location in the subtropical monsoon climate zone on the east coast of Eurasia 22,23 . As a result, floods occur frequently in the Yangtze River Basin and are usually characterized by a strong sudden occurrence, significant areal extent, and massive loss of lives and property 24,25 . ...
Five severe floods occurred in the Yangtze River Basin, China, between July and August 2020, and the Three Gorges Reservoir (TGR) located in the middle Yangtze River experienced the highest inflow since construction. The world’s largest cascade-reservoir group, which counts for 22 cascade reservoirs in the upper Yangtze River, cooperated in real time to control floods. The cooperation prevented evacuation of 600,000 people and extensive inundations of farmlands and aquacultural areas. In addition, no water spillage occurred during the flood control period, resulting in a world-record annual output of the TGR hydropower station. This work describes decision making challenges in the cooperation of super large reservoir groups based on a case-study, controlling the 4th and 5th floods (from Aug-14 to Aug-22), the efforts of technicians, multi-departments, and the state, and reflects on these. To realize the full potential of reservoir operation for the Yangtze River Basin and other basins with large reservoir groups globally, we suggest: (i) improve flood forecast accuracy with a long leading time; (ii) strengthen and further develop ongoing research on reservoir group cooperation; and (iii) improve and implement institutional mechanisms for coordinated operation of large reservoir groups.
Hydrological time series (HTS) are the key basis of water conservancy project planning and construction. However, under the influence of climate change, human activities and other factors, the consistency of HTS has been destroyed and cannot meet the requirements of mathematical statistics. Series division and wavelet transform are effective methods to reuse and analyse HTS. However, they are limited by the change-point detection and mother wavelet (MWT) selection and are difficult to apply and promote in practice. To address these issues, we constructed a potential change-point set based on a cumulative anomaly method, the Mann–Kendall test and wavelet change-point detection. Then, the degree of change before and after the potential change point was calculated with the Kolmogorov–Smirnov test, and the change-point detection criteria were proposed. Finally, the optimization framework was proposed according to the detection accuracy of MWT, and continuous wavelet transform was used to analyse HTS evolution. We used Pingshan station and Yichang station on the Yangtze River as study cases. The results show that (1) change-point detection criteria can quickly locate potential change points, determine the change trajectory and complete the division of HTS and that (2) MWT optimal framework can select the MWT that conforms to HTS characteristics and ensure the accuracy and uniqueness of the transformation. This study analyses the HTS evolution and provides a better basis for hydrological and hydraulic calculation, which will improve design flood estimation and operation scheme preparation.
The streamflow characteristics within the Yangtze River Basin have experienced substantial fluctuations in recent years because of the combined effects of environmental factors and intensive human activities. In this study, at the Datong station, two coastal acoustic tomography (CAT) systems were used to track the Yangtze River discharge from July 2018 to January 2021. The stage–discharge relationship presented large uncertainties because of the Three Gorges Dam (TGD) operations, whereas the CAT method performed effectively in discharge monitoring even during extreme flood events. The distribution of downstream discharge was concentrated because of the regulation by the TGD. Analysis of the potential drivers in the downstream river hydrology reveals that the effect of rainfall events (leading to a maximum of ~40% changes) was heavily influenced by the regulation by the TGD (at least 50% contribution). Additionally, the river–tide process is also sensitive to the discharge regulated by the TGD. The discharge induced by tidal waves was negligible (a maximum of 1.11% change). This work demonstrates that an acoustic method can effectively monitor the massive flood discharge in unsteady flow conditions in large rivers, thereby facilitating the management of large-scale dam- and tide-influenced river systems.
Hydrological time series (HTS) is the key basis of water conservancy project planning and construction. However, under the influence of climate change, human activities and other factors, the consistency of HTS has been destroyed and cannot meet the requirements in mathematical statistics. It is urgent to find a better way to divide HTS. Wavelet transform is an effective way to catch the evolution of HTS, but its accuracy is highly dependent on the mother wavelet (MWT). To address these issues, we constructed a potential changepoint set based on two traditional detection methods and wavelet changepoint detection (WTCPD). Then, the degree of change before and after the potential changepoint was calculated with the Kolmogorov-Smirnov test, and a changepoint detection framework (CPDF) was proposed. Finally, according to the difference of detection accuracy between MWT in WTCPD, a mother wavelet optimal framework (MWTOF) was proposed, and continuous wavelet transform was carried out to analyse HTS evolution. We used Pingshan Station and Yichang Station in the Yangtze River as study cases. The result shows: (1) CPDF can quickly locate potential changepoints, determine the change trajectory and complete the division of HTS. (2) MWTOF can select the MTW that conforms to HTS characteristics and ensure the accuracy and uniqueness of the transformation. This study analyses the HTS evolution and provides a better basis for hydrological and hydraulic calculation, which will improve the design flood estimation and the operation scheme preparation.
