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Following the May 2000 Cerro Grande fire at Los Alamos, NM, surface water control structures were constructed near Los Alamos to mitigate the transport of contaminant-bearing sediment toward the Rio Grande river due to increased runoff caused by the removal of vegetation by the fire. A low-head weir was constructed in Los Alamos Canyon, 5 km to the...
Contexts in source publication
Context 1
... surface casings were and keep them isolated (Stone and Newell 2002). Figure 3 illustrates the screen and port locations in LAWS-01, as well set for the three boreholes using hollow-stem augering. Augers were advanced through the canyon alluvium to the top of the as the conceptual model of subsurface hydrogeology based on data from the three LAWS boreholes and upstream Wells basalt (≈3 m [10 ft] bgs) using 30-cm (12-in) augers, and 27-cm (10.75-in)-o.d. ...
Context 2
... asl, parallel to Port 2 mately 40 m (131 ft), coinciding with the clay-rich hori- zon and massive basalt unit, and the expected position behavior, in general. At Port 4, groundwater has been present through the entire study period at a relatively of perched water derived from the conceptual model. The final (revised) conceptual model presented in Fig. 3 constant elevation of 1880 to 1881 m (6168-6172 ft) asl. The relationship between groundwater elevations, depicts geology based on this ...
Citations
... It prevented flooding during the wet season and increased river flows during the dry season [10,11]. The associated river environment changes also affected groundwater flow and quality, owing to stream-aquifer interactions, which in turn affected groundwater use near the river [12,13]. ...
During the cold dry season, a large amount of groundwater is pumped for water-curtain cultivation in agricultural fields mostly located near the four major rivers of South Korea. Several weirs, installed previously to secure sufficient water resources from these rivers, were opened in 2017 for restoring the riverine environment. Weir-controlled river level fluctuations have altered stream–aquifer interactions, leading to groundwater drawdown. In this study, changes in stream–aquifer interaction caused by seasonal pumping and weir opening were investigated, using Visual MODFLOW. Two indexes that considered the pump type and aquifer characteristics—the pumping available thickness (PAT) and aquifer productivity index (API)—were used to analyze the effects of weir opening on seasonal groundwater use. Our simulations indicated that weir opening had a large impact on seasonal groundwater use due to groundwater drawdown, especially with respect to centrifugal pumps located in low transmissivity areas where the API decreased after the weir was opened. The resulting decrease in groundwater pumping rates would lower the thermal effect of the water-curtain greenhouse process. This indicates that water supply alternatives are needed so that the weirs can be operated efficiently and field requirements can be met, while the deleterious effects on groundwater are avoided.
... The variations in the river water level change the groundwater flow in riparian areas, leading to changes in the water balance [14]. This could also affect stream-aquifer interactions [15]. ...
The Juksan weir, installed in the Yeongsan river in South Korea from 2010 to 2012, has secured sustainable water resources and helped control flooding. However, low river flow velocities due to the weir have deteriorated the quality of the river water. For natural river restoration, the water gate was opened in 2017. In this study, the three-dimensional finite difference model Visual MODFLOW was used to analyze the effects of gate opening on stream–aquifer interactions. A conceptual model was developed to simulate the stream–aquifer dynamics caused by the operation of the water gate at the Juksan weir. Groundwater data were also analyzed to determine the impacts of weir operations on groundwater quality. Our results indicate that a lower river level due to the weir opening changed the groundwater flow, which then affected the water balance. The change in groundwater flow increased the variability of the groundwater quality which had homogenized because of induced recharge after the construction of the weir. This could affect groundwater use in agricultural areas near the weir. Therefore, further groundwater monitoring and hydrodynamic analyses are required to anticipate and address any potential issues.
... The hydraulic gradient and riverbed permeability are important factors that determine stream-aquifer interaction [23]. A change in hydrological conditions due to variations in the river level can cause rapid transport of contaminants between an aquifer and a river [24,25], affecting the groundwater quality and aquatic ecosystems [26,27]. ...
Hydraulic structures have a significant impact on riverine environment, leading to changes in stream–aquifer interactions. In South Korea, 16 weirs were constructed in four major rivers, in 2012, to secure sufficient water resources, and some weirs operated periodically for natural ecosystem recovery from 2017. The changed groundwater flow system due to weir operation affected the groundwater level and quality, which also affected groundwater use. In this study, we analyzed the changes in the groundwater flow system near the Geum River during the Baekje weir operation using Visual MODFLOW Classic. Groundwater data from 34 observational wells were evaluated to analyze the impact of weir operation on stream–aquifer interactions. Accordingly, the groundwater discharge rates increased from 0.23 to 0.45 cm/day following the decrease in river levels owing to weir opening, while the hydrological condition changed from gaining to losing streams following weir closure. The variation in groundwater flow affected the groundwater quality during weir operation, changing the groundwater temperature and electrical conductivity (EC). Our results suggest that stream–aquifer interactions are significantly affected by weir operation, consequently, these repeated phenomena could influence the groundwater quality and groundwater use.
... Numerous borehole-based approaches have been developed for monitoring a variety of properties and processes over widely ranging depths in soils and consolidated rocks (Dahan et al., 2009;Faybishenko, 2000;Hubbell et al., 2004;Levitt et al., 2005;Rimon et al., 2007;Salve, 2011;Sisson et al., 2002;Tokunaga, p. 3 of 14 1992). However, floodplains in mountainous regions commonly contain cobbles that make borehole instrumentation difficult. ...
Core Ideas
A significant fraction of CO 2 fluxes from a semiarid floodplain originates from below the root zone.
Measured and calculated field CO 2 fluxes are consistent.
Laboratory‐measured respiration rates are consistent with field results.
Although CO 2 fluxes from soils are often assumed to originate within shallow soil horizons (<1‐m depth), relatively little is known about respiration rates at greater depths. We compared measured and calculated CO 2 fluxes at the Rifle floodplain along the Colorado River and measured CO 2 production rates of floodplain sediments to determine the relative importance of deeper vadose zone respiration. Calculations based on measured CO 2 gradients and estimated effective diffusion coefficients yielded fluxes that are generally consistent with measurements obtained at the soil surface (326 g C m ⁻² yr ⁻¹ ). Carbon dioxide production from the 2.0‐ to 3.5‐m depth interval was calculated to contribute 17% of the total floodplain respiration, with rates that were larger than some parts of the shallower vadose zone and underlying aquifer. Microbial respiration rates determined from laboratory incubation tests of the sediments support this conclusion. The deeper unsaturated zone typically maintains intermediate water and air saturations, lacks extreme temperatures and salinities, and is annually resupplied with organic carbon from snowmelt‐driven recharge and by water table decline. This combination of favorable conditions supports deeper unsaturated zone microbial respiration throughout the year.
... Dahan et al. [2007Dahan et al. [ , 2008 and Rimon et al. [2007] used this system to monitor natural and anthropogenic infiltration events and estimate recharge to groundwater. Inclined boreholes have also been used to access otherwise inaccessible regions of the subsurface; for example, below ponds and landfills where vertical drilling is either impractical or undesirable [e.g., Levitt et al., 2005;Mclin et al., 2005]. ...
[1] Angled boreholes have been proposed to improve water content and pressure head monitoring in deep vadose zones by reducing the impact of the borehole on measurements by placing sensors below undisturbed soil. However, the borehole casing distorts the flow field, which may impact measurements made with sensors placed on or in the boreholes. We examined a wide range of soil types, background fluxes, and casing radii and angles of inclination to predict the error in water content and pressure head measurements that arise due to this flow disruption under unit gradient flow. We found that placing pressure head and water content sensors 110° and 120° from the top of the borehole, respectively, minimizes the effects of flow perturbation. Under some conditions, it may be possible to use the perturbation of the flow field caused by the casing to estimate hydraulic parameter values.
... Dahan et al. [2007], Rimon et al. [2007], and Dahan et al. [2008] used this system to monitor natural and anthropogenic infiltration events and estimate recharge to groundwater. Inclined boreholes have also been used to access otherwise inaccessible regions of the subsurface; for example, below ponds and landfills where vertical drilling is either impractical or undesirable [e.g., Levitt et al., 2005 andMclin et al., 2005]. ...
In the present scenario, the conservation of water is the main concern of human beings. The depletion rate of water is rapid for surfacewater as well as for groundwater. In most of the landscapes, surfacewater and sub-surface water are inter-connected to each other, and the interaction between sub-surface water and surfacewater is a complex phenomenon. Remarkable advances in groundwater (sub-surface water) flow modelling have been influenced by the water demand which enables to prediction impacts of human activities on groundwater systems and associated environment. The main objective of this paper is to find out the different methods to predict the exchange of fluxes between groundwater and surfacewater. A case study of Varanasi district, India has been taken. In this, landfill sites were selected, and the impact of leachate parameters on the river water (surfacewater) was observed. Inter-relationship of groundwater with surfacewater was found and how much time it takes in reaching to the river. The steady state of the groundwater model is conceptualized by using groundwater flow modelling program. The conceptualization of the groundwater model needed so much input data, and compilation of this data is another tedious task. Combining with Geographic Information System (GIS) technology Groundwater Modeling System (GMS) provided good visualization interface for the user and played a significant role in groundwater evaluation and management. Various processes affect the groundwater and surface water interaction, such as flood recharge, evapo-transpiration from open/shallow water-bodies, interception of water by wetlands, para-fluvial flow. This study helps in choosing the appropriate modelling tools for groundwater and surface water interaction, done by striking the right balance between groundwater and surfacewater processes. The technique used in selecting the most suitable tool of the groundwater model is based upon the various parameters and processes associated with the groundwater/surfacewater. Depending upon the level of complexity of the model, various software packages are used.
The modeling of thick vadose zones is particularly challenging because of difficulties in collecting a variety of measured sediment properties, which are required for parameterizing the model. Some models rely on synthetic data, whereas others are simplified by running as homogeneous sediment domains and relying on a single set of sediment properties. Few studies have simulated flow processes through a thick vadose zone using real and comprehensive data sets comprising multiple measurements. Here, we develop a flow model for a 7‐m‐thick vadose zone. This model, combining the numerical codes CTRAN/W with SEEP/W, includes the measured sediment hydraulic properties of the investigated vadose zone and incorporates the actual climate and subsurface conditions of the study site (precipitations, water‐table elevations, and stable isotope data). The model is calibrated by fitting the simulated and measured vertical profiles of water content. Our flow model calculates a transit time of one year for the travel of water through the 7‐m vadose zone; this estimate matches stable isotope–based results obtained previously for this site. A homogeneous sediment domain flow model, which considers only a single set of sediment properties, produces a transit time that is approximately half the duration of that of the heterogeneous flow model. This difference highlights the importance of assuming heterogeneous material within models of thick vadose zones and testifies to the advantage gained when using real sediment hydraulic properties to parametrize a flow model.
Wells designated as groundwater under the direct influence of surface water (GUDI) have caused an ongoing boil‐water‐advisory afflicting the island of Tutuila, American Samoa for almost a decade. Regulatory testing at these wells found turbidity and indicator bacteria spikes correlated with heavy rainfall events. However, the mechanism of this contamination has, until now, remained unknown. Surface water may reach wells through improperly sealed well casings, or through the aquifer matrix itself. In this study, three independent surface‐water tracers, turbidity, indicator bacteria, and water isotopes were used to assess recharge timing and determine contamination mechanisms. Results from each method were reasonably consistent, revealing average GUDI well breakthrough times of 37 ± 21 hours for turbidity, 18 to 63 hours for bacteria, and 1 to 5 days for water isotopes. These times match well with estimated subsurface flow rates through highly‐permeable aquifer materials. In contrast, where one well casing was found to be compromised, turbidity breakthrough was observed at 3 to 4 hours. These results support local management decisions, and show repairing or replacing wells will likely result in continued GUDI contamination. Additionally, differences in observed rainfall response for each tracer provide insight into the recharge dynamics and subsurface flow characteristics of this and other highly‐conductive young‐basaltic aquifers.
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MIM 1D transport model was successfully applied to simulate the asymmetric behavior observed in three breakthrough curves of tracer tests performed under natural gradient conditions in a phreatic fractured volcanic aquifer. The transport parameters obtained after adjustment with a computer program, suggest that only 50% of the total porosity effectively contributed to the advective-dispersive transport (mobile fraction) and the other 50% behaved as a temporary reservoir for the tracer (immobile fraction). The estimated values of hydraulic properties and MIM model parameters are within the range of values reported by other researchers. It was possible to establish a conceptual and numerical framework to explain the three-tracer tests curves behavior, despite the limitations in quality and quantity of available field information.
