Stream-aquifer Interaction Research Articles

Comprehensive, Multi‐Scale Evaluation of Field Methods for Assessing Stream–Aquifer Interactions Along Channelised Lowland Streams

ABSTRACTStream–aquifer interactions (SAIs) play a critical role in effective groundwater management, yet their complex dynamics remain poorly understood in channelized lowland perennial streams. This study presents a multi‐scale, multi‐technique investigation of SAIs along two long‐stream reaches in Tennessee, United States. The goal is to define a suitable methodology for characterising SAIs in this specific hydrological setting, serving as a starting point for developing a more standardised and replicable approach. The methodology includes an initial evaluation of various field techniques, followed by extensive surveys using potentiomanometers, electromagnetic induction (EMI), vertical temperature profilers (VTPs) and complementary methods such as seepage meters, bank tests and well‐data analyses. Results reveal distinct hydrogeomorphic behaviours across and along the streams, challenging the SAI‐homogeneity notions typically assumed in groundwater models. Nonconnah Creek exhibited streambed colmation and negligible hydraulic gradients, resulting in disconnection from the aquifer during low flows, except for a 300‐m losing reach with high downward gradients. In contrast, the Loosahatchie River displayed relatively homogeneous streambed properties and small, upward hydraulic gradients, suggesting uniform SAIs along the surveyed reaches. EMI proved highly effective for mapping streambed sediments quickly, while potentiomanometers accurately measured small head differences critical for understanding SAI dynamics. VTPs were less practical due to the extended data‐collection times required and their vulnerability to flooding. This study emphasises the importance of multi‐scale investigations using diverse techniques to accurately characterise SAIs in lowland streams, highlighting the confounding influences of geological formations, anthropogenic alterations and depositional processes on groundwater–surface water interactions. The findings contribute to refining local water balances, informing groundwater management strategies and underscoring the need for incorporating local‐scale field data into regional groundwater models. The proposed methodology serves as a foundation for developing a standardised approach for characterising SAIs in lowland channelized perennial streams, adaptable for similar stream systems worldwide.

Estimating exploitable groundwater for agricultural use under environmental flow constraints using an integrated SWAT-MODFLOW model

Traditionally, the impact of groundwater abstraction on streamflow and aquifers has been assessed primarily in terms of water availability and depletion, often neglecting critical environmental flow (Eflow) requirements. To address this gap, our study employed an Eflow perspective to evaluate exploitable groundwater for agricultural use at a watershed scale using an integrated modeling approach. We used the SWAT-MODFLOW model, integrating the Soil and Water Assessment Tool (SWAT) and the Modular Finite-Difference Flow Model (MODFLOW), to analyze water balance segments and stream-aquifer interactions in the study region. Eflow for different management classes was determined using the flow duration curve (FDC) approach. The FDC method classifies Environmental Flow Management Classes (EMC) from “A” (natural or minor alteration) to “F” (critically modified). The relationship between the selected EMC and simulated streamflow, under the pressure of agricultural groundwater pumping, served as a constraint in evaluating exploitable groundwater alongside groundwater level fluctuations. As the traditional approach depends on average recharge for determining exploitable groundwater, this study also assessed the spatiotemporal distribution of groundwater recharge. Simulation periods were aligned with agricultural pumping schedules. Results indicated that groundwater pumping significantly impacts streamflow at the start of the irrigation period. Under moderately affected EMC and with an average groundwater level fluctuation of one meter, the exploitable groundwater during the irrigation period can reach up to 2.96 Mm3/day. With this amount of pumping, the average groundwater discharge to streams declined by around 13 %. While groundwater level fluctuations near the watershed outlet were minimal, in the upstream area, levels could decrease by as much as 2.5 m. The groundwater level fluctuation underscores the necessity of accounting for both spatial and temporal factors, particularly in highly affected regions.

Optimal pumping policy from well field connected with a stream

Conjunctive use management of water resources is of paramount importance in the backdrop of the growing demand for freshwater resources. With this viewpoint, this study is aimed to present a methodological approach utilizing the combined use of simulation and optimization models for evolving strategies or policies for the management of water resources in a well-field connected to a stream. The proposed methodology incorporates the coupling of the groundwater simulation model with the optimization model for decision-making through the response matrix method. In this study, a numerical groundwater flow model using MODFLOW was used to simulate the response of stream-aquifer interactions. A linear optimization model was formulated to account for the best optimal groundwater withdrawal taking into consideration the allowable drawdown, permissible stream flow depletion, and satisfaction of the water demands. Such management options permit the investigation of alternative strategies for groundwater abstraction in a well-field hydraulically connected to a stream for sustainable development of water resources. The model was applied in a hypothetical well field study area hydraulically connected to a stream and satisfactory results were obtained. The methodology was also very important to understand the tradeoff between groundwater withdrawal and the depletion of flow to the nearby stream. This approach was applied to the Aynalem well field stream-aquifer system which is located in Northern Ethiopia. Results show that groundwater extraction from the Aynalem well field triggers stream flow depletion and it is possible to decrease the stream flow depletion by 3.5–4.5% by adjusting current groundwater withdrawal schedules and configuration of existing wells.

Developing a conceptual model of groundwater – Surface water interactions in a drought sensitive lowland catchment using multi-proxy data

Frequencies and intensities of droughts have increased due to climate change, providing an urgent impetus to improve understanding of ecohydrological fluxes in drought-sensitive areas where water and food security are threatened. We used a multi-proxy approach for assessing the effects of landuse and catchment properties on recharge and groundwater – surface water interactions during a prolonged drought starting in summer 2018 in a 66 km2 lowland, mixed landuse catchment (Demnitzer Mill Creek, Germany). We used water table monitoring, water stable isotopes, tritium isotopes, hydrogeochemical tracers, streamflow observations and geophysical investigations to characterise the spatial and temporal patterns of groundwater recharge in a shallow, unconfined aquifer system. Long-term groundwater levels showed a declining trend since 2011, which accelerated after 2018 resulting in increasingly intermittent streamflow. Geophysical surveys and groundwater monitoring indicated that shallow water tables (typically < 3 m deep) in low to moderate permeability surficial deposits are generally recharged during winter, leading to higher groundwater – surface water connectivity in riparian alluvial aquifers, which is the first order control on streamflow generation. This was supported by similar geochemical characteristics of groundwater and streamflow. Water stable isotopes indicated a high damping in groundwater with a bias towards winter precipitation and direct recharge. Groundwater age estimates using tritium showed high uncertainty but indicated that shallow groundwater was < 10 years old and generally similar to streamflow. Such multi-proxy approaches help understand changes in groundwater recharge and stream-aquifer interactions during droughts and contribute to the development of sustainable land and water management strategies for groundwater systems that are sensitive to climate change.

Modeling of water table profile variations owing to stream-aquifer interaction.

Spatial and temporal variations of the water table could be explained by the one-dimensional Boussinesq equation by incorporating the variables of evapotranspiration and groundwater recharge with appropriate initial and boundary conditions. In this study, the stream-aquifer interaction has been investigated through a numerical example model with the implementations of Galerkin's method-based Finite Element Solution (FES), Hybrid Finite Analytic Solution (HFAS), Fully Implicit Finite Difference Solution (FIFDS) of one-dimensional nonlinear Boussinesq equation, and analytical solutions of the Boussinesq equation linearized by Baumann's transformation (AS I) as well as linearized by Werner's transformation (AS II). Considering HFAS as the benchmark solution, it was observed that in both recharging and discharging aquifers, water table profiles at 1 day and 5 days as obtained from FES followed by FIFDS were observed quite close to HFAS. Based on L2 and Tchebycheff norms, FES and FIFDS were ranked in first and second place, respectively. L2 and Tchebycheff norms could not consistently establish the performance ranking of analytical solutions but their performance ranking was certainly below the numerical solutions. The performance ranking of analytical solutions could not consistently be established using the L2 and Tchebycheff norms, but it was certainly below the numerical solutions.

Understanding the exchange process between ground and surface water using mini drive point piezometer and mathematical models to identify suitable managed aquifer recharge sites.

In the current study, subsurface characteristics within the complex formation of the Shilabati basin system of West Bengal, India, extending over an area of 3888 km2, have been estimated using a cost-effective piezometer and MIKE FEFLOW package based on a steady-state numerical model. Pore size and fine particle content of streambeds are affected by two opposing flow contraptions. Such opposite flow conditions are likely to affect the hydraulic conductivity of the streambed. However, analogies of the hydraulic conductivity (Kh) of streambeds for losing and gaining streams have not been well documented in the recent past. The Kh value from the piezometer has been highest at the Dakshin Pairachali site (6.765 m/day), with the stream gaining water from the discharge of the local aquifer. Analysis of the stream-aquifer interaction using the FEFLOW model has allowed us to understand the groundwater water head of the basin ranging from 160.33 to 0.32 m.a.s.l (meters above sea level). The present study also constitutes the first attempt for the identification of suitable sites for the implementation of managed aquifer recharge (MAR) technology in West Bengal, India, to manage extreme drought events. The suitable sites have been identified by means of three fuzzy multi-criteria decision analysis based on nine criteria: river discharge, moisture content, porosity, drainage type, rainfall, land use type, geology, aquifer material, and hydraulic conductivity. To design a radial collector well and infiltration gallery for the selected site in an anisotropic, homogeneous, unconfined, and semi-infinite aquifer near a fully penetrating stream, a pumping test has been conducted to optimize a safe yield of 12.096 MLD (megaliters per day).

Investigating river–aquifer interactions using heat as a tracer in the Silala river transboundary basin

AbstractThis article reviews scientific studies in which heat was used as a natural tracer to investigate stream–aquifer interactions in the Silala River in Chile and provide evidence that was used to support a legal dispute between Chile and Bolivia over the status and use of the waters of this watercourse. Streambed temperature time series at various locations downstream of the Chile‐Bolivia international border showed that water flows downwards through the streambed sediments, from the river towards the fluvial aquifer. These findings are consistent with hydraulic head measurements performed at the study site. Additionally, fiber‐optic distributed temperature sensing (FO‐DTS) methods were employed to observe river temperatures with a spatial resolution of the order of 0.5 m in a river reach of ~1.3 km. FO‐DTS technology allowed detection of various warm springs that discharged their waters into the Silala River, as well as the location of an artesian well that supplies the river with ~90 L/s of deep groundwater at ~20 °C. The results provided improved understanding of the Silala River hydrogeology, and were used to calibrate and validate a groundwater model of the system, reported elsewhere. Both methodologies demonstrated that the river is indeed a system of surface waters and groundwaters interacting as a unitary whole, a key aspect of the definition of an international watercourse, and generated valuable scientific evidence to support a major international legal dispute.This article is categorized under: Science of Water &gt; Hydrological Processes Science of Water &gt; Methods

Study of dilution processes of sulfidic aquifer hosted by the Fiume-Vento karstic complex, Frasassi (Central Italy)

Sulfuric acid caves are widespread worldwide. In Central Italy, the Fiume-Vento karstic complex represents the most important active hypogenic cave system hosting several interconnected lakes where groundwater moves towards sulfidic springs emerging along the Sentino Stream. Stratification and dilution phenomena between freshwater and sulfidic water occur in many underground lakes, even if they remain still open if these processes are driven by stream-aquifer interaction or dripping water. The speleological knowledge coupled with geochemical surveys can help study groundwater circulation in the karst system’s inner and outer portions. The geochemical analyses on water samples taken along the Sentino Stream, inside the caves (dripping and lakes water) and in sulfidic springs allow establishing the origin of the dilution water in the dripping water. However, stream-aquifer interactions cannot be excluded during flood events. Using the tracer masse balance method (chloride and sodium ions), the discharge of the sulfidic springs ranges between 65 and 11 L/s. The results presented in this study may help understand groundwater circulation and dilution phenomena in other karst systems characterised by sulfuric acid speleogenesis type.

Alternative stable states and hydrological regime shifts in a large intermittent river

Non-perennial rivers and streams make up over half the global river network and are becoming more widespread. Transitions from perennial to non-perennial flow are a threshold-type change that can lead to alternative stable states in aquatic ecosystems, but it is unknown whether streamflow itself is stable in either wet (flowing) or dry (no-flow) conditions. Here, we investigated drivers and feedbacks associated with regime shifts between wet and dry conditions in an intermittent reach of the Arkansas River (USA) over the past 23 years. Multiple lines of evidence suggested that these regimes represent alternative stable states, including (a) significant jumps in discharge time series that were not accompanied by jumps in flow drivers such as precipitation and groundwater pumping; (b) a multi-modal state distribution with 92% of months experiencing no-flow conditions for <10% or >90% of days, despite unimodal distributions of precipitation and pumping; and (c) a hysteretic relationship between climate and flow state. Groundwater levels appear to be the primary control over the hydrological regime, as groundwater levels in the alluvial aquifer were higher than the stream stage during wet regimes and lower than the streambed during dry regimes. Groundwater level variation, in turn, was driven by processes occurring at both the regional scale (surface water inflows from upstream, groundwater pumping) and the reach scale (stream–aquifer exchange, diffuse recharge through the soil column). Historical regime shifts were associated with diverse pressures including network disconnection caused by upstream water use, increased flow stability potentially associated with reservoir operations, and anomalous wet and dry climate conditions. In sum, stabilizing feedbacks among upstream inflows, stream–aquifer interactions, climate, vegetation, and pumping appear to create alternative wet and dry stable states at this site. These stabilizing feedbacks suggest that widespread observed shifts from perennial to non-perennial flow will be difficult to reverse.

Steady vs dynamic stream-aquifer interactions: Lower Flint River Basin, Southwest Georgia, USA

Study regionThe Lower Flint River Basin (LFRB): a karst catchment in southwestern Georgia, USA. Study focusA year-long field campaign from July 2018 to July 2019 measured steady and dynamic stream-aquifer exchanges on Ichawaynochaway Creek (INC), a fifth-order tributary to the karstic Flint River in Georgia. The net change in discharge along a 24-km Creek segment was determined between two US Geological Survey gaging stations with no surface-water inflows. Stream-aquifer interactions were measured along a 120-m piezometer transect perpendicular to the bank. Hydraulic parameters to aid future modeling efforts were estimated using the method of moments applied to changes in bank flow direction from Hurricane Michael. New hydrological insights for the regionResults display the effects of local water use on streamflow as most channel storage gains occurred in the fall and winter. Negligible net channel gains and some losses occurred during the spring and summer months. Approximately 150 million m3 of net channel gains were observed during the study period. Initial stormflow contributed to aquifer recharge as indicated by reversals in the hydraulic gradient. Diffusivity and transmissivity increased along the transect (9–420 m2/d) and (3–150 m2/d), respectively, and hydraulic conductivity equaled 2.85 m/d. Stream-reach orientation with respect to regional groundwater gradients explains increased stream-aquifer interactions. Surface-groundwater interactions in karst systems are better understood after characterizing variation of hydraulic processes.

Effects of Weir Operation on Seasonal Groundwater Use: A Case Study of the Han River, South Korea

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.

Nutrient dynamics in stream water and groundwater in riparian zones of a mesoscale agricultural catchment with intense seasonal pumping

Water and soil in agricultural areas are usually enriched with nutrients from excessive fertilizations. Riparian zones, the interfaces between terrestrial and aquatic systems, play crucial roles in delivery of the nutrients to groundwater and surface water. We evaluated spatiotemporal variations of water flow and nutrients in a mesoscale agricultural catchment along the riparian zones of the main stream for dry and rainy season by hydrologic monitoring and measurements of hydrochemical parameters and water stable isotopes. Gaining stream conditions were dominant in the mountainous upper reaches with steep topographic gradient while groundwater level in the lower basin considerably varied seasonally due to intense groundwater pumping to aid in heating greenhouses in winter season, which resulted in losing stream conditions during the dry season. Compared to shallow groundwater, deep groundwater had higher nitrate concentration derived from dry farmland in hilly terrains and induced recharge due to the groundwater pumping. Nitrate concentration was significantly higher in groundwater than that in stream water, indicating that groundwater is a major source of nitrate in stream water considering mainly gaining stream conditions. Compared to stream water, dissolved phosphorus concentration was higher in shallow groundwater recharged from paddy fields and floodplain areas with reducing conditions, evaporation signature of water stable isotopes, and lower nitrate concentration. Nutrient flux estimates for the catchment revealed that nitrate in stream water is considerably contributed by groundwater discharge and shallow groundwater in reducing conditions is a significant source of dissolved phosphorus in stream water, which was more pronounced in the rainy season. This study demonstrated that intense agricultural activities in riparian zones strongly affect stream-aquifer interactions and nutrient delivery to the stream, as well as groundwater. These findings can contribute to understanding hydrological and biogeochemical processes of nutrients in agricultural catchments and establishing an effective management of water use and nutrient application.

Streams, sewage, and shallow groundwater: stream-aquifer interactions in the Kathmandu Valley, Nepal

The Kathmandu Valley in Nepal is facing a water quantity and quality crisis due to rapid urbanization and haphazard water and wastewater planning and management. Annually, groundwater extractions in the Kathmandu Valley exceed capture, resulting in groundwater table declines. Streams are often important sources of recharge to (or destination of discharges from) aquifers. However, stream-aquifer interactions in the Kathmandu Valley are poorly understood. To improve this understanding, we performed topographic surveys of water levels, and measured water quality, in streams and adjacent hand-dug wells (shallow aquifer). In pre-monsoon, 12% (2018) and 44% (2019) of wells had water levels higher than adjacent streams, indicating mostly a loss of stream water to the aquifer. However, in post-monsoon, 69% (2018) and 70% (2019) of wells had water levels higher than adjacent streams, indicating that monsoon rainfall contributes to shallow aquifer recharge which, at least temporarily, causes streams to transition from losing to gaining. Concentrations of all water quality parameters (electrical conductivity, ammonia, alkalinity, and hardness) were higher in the pre-monsoon compared to post-monsoon in both streams and wells. There was no recurring trend in water level difference longitudinally from upstream to downstream. However, water quality in streams and wells depleted from upstream to downstream. While we clearly observed seasonal refilling of the shallow aquifer, the role of the deep aquifer in seasonal storage processes deserve future research attention.

Perturbation solutions of the Boussinesq equation for horizontal flow in finite and semi-infinite aquifers

Groundwater flow in an unconfined aquifer can be described by the Boussinesq equation. The Boussinesq equation is nonlinear and approximate solutions exist only for specific flow conditions. In the present work, the nonlinear equation is tackled analytically via a refinement of its linearized solution in a perturbation series framework. The perturbation series solution applies for any time-dependent variation of the stream level, and they are evaluated for various flow recharge and drainage conditions. Particular results for a sudden change and a piecewise linear variation are presented for both finite and semi-infinite aquifers. The approximate solutions can simulate the original nonlinear behavior with high accuracy due to the introduction of the representative depth parameter α that is evaluated in an optimal fashion for any given flow condition. The derivation of the optimal α parameter has also allowed the generalization and improvement of the classical series results pertaining to the abrupt rise or drop of the stream level in a semi-infinite aquifer. In the case of a gradual variation of the stream level in a finite aquifer domain, the linear solution with a time-varying estimate of α is of sufficient accuracy for practical purposes. Explicit algebraic expressions are presented for the exchange flow rates and the associated flow volumes that are of prime interest in stream-aquifer interaction studies.

Changes in Stream–Aquifer Interactions Due to Gate Opening of the Juksan Weir in Korea

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.

Assessment of impact in groundwater levels and stream-aquifer interaction due to increased groundwater withdrawal in the lower Apalachicola-Chattahoochee-Flint (ACF) River Basin using MODFLOW

Study regionLower Apalachicola-Chattahoochee-Flint (ACF) River Basin, southeastern United States (U.S.). Study focusExcessive groundwater withdrawal for irrigation from the Upper Floridan Aquifer is an important issue in the lower ACF River Basin as it has led to decline in groundwater levels as well as reduction in baseflows. Since the withdrawal is projected to further increase in the future, this study evaluated the impacts of the projected increase in irrigation on the groundwater levels as well as the stream-aquifer flux in the region. The study also identified regions that are most important for groundwater recharge. New hydrological insights into the regionEvaluation of the geohydrologic zones identified Upland Instream Karst as the most sensitive zone for recharge into the aquifer while zones in the region where the aquifer thickness was comparatively lower and close to the land surface was generally identified as sensitive. Simulation of the projected irrigation scenario predicted a reduction in groundwater levels by as much as 2.38 m, while a general reduction was predicted in much of the model domain. Large groundwater level reductions were mostly predicted in regions where the aquifer is comparatively thinner. Evaluation of the changes in stream-aquifer flux showed that flux reduced by as much as 33 % with large reductions predicted in the Lower Flint and Kinchafoonee watersheds. This study also helped identify localized zones and stream sections most susceptible to the impacts of increase in irrigation.

Assessing Stream-Aquifer Connectivity in a Coastal California Watershed

We report the results of field and laboratory investigations of stream-aquifer interactions in a watershed along the California coast to assess the impact of groundwater pumping for irrigation on stream flows. The methods used include subsurface sediment sampling using direct-push drilling, laboratory permeability and particle size analyses of sediment, piezometer installation and instrumentation, stream discharge and stage monitoring, pumping tests for aquifer characterization, resistivity surveys, and long-term passive monitoring of stream stage and groundwater levels. Spectral analysis of long-term water level data was used to assess correlation between stream and groundwater level time series data. The investigations revealed the presence of a thin low permeability silt-clay aquitard unit between the main aquifer and the stream. This suggested a three layer conceptual model of the subsurface comprising unconfined and confined aquifers separated by an aquitard layer. This was broadly confirmed by resistivity surveys and pumping tests, the latter of which indicated the occurrence of leakage across the aquitard. The aquitard was determined to be 2–3 orders of magnitude less permeable than the aquifer, which is indicative of weak stream-aquifer connectivity and was confirmed by spectral analysis of stream-aquifer water level time series. The results illustrate the importance of site-specific investigations and suggest that even in systems where the stream is not in direct hydraulic contact with the producing aquifer, long-term stream depletion can occur due to leakage across low permeability units. This has implications for management of stream flows, groundwater abstraction, and water resources management during prolonged periods of drought.

A simplified approach for the evaluation of groundwater flow in stream–aquifer interaction

Stream–aquifer interaction process plays an important role in modulating flood wave propagation in a channel. The most elementary understanding of stream–aquifer interaction can be interpreted by the flux direction between a surface water body and the underlying aquifer. At the time of floods, stream stage rises, and the water gets infiltrated into the aquifer, and this process gets reversed at the time when the stream stage gets declined. Therefore, an integrated mechanism between the surface and subsurface flows is particularly important for models, where the response of the system is based on simultaneous interactions between these two major flow domains. In this study, numerical simulation of a flood wave has been demonstrated considering stream–aquifer interaction. The calibration has been executed on a hypothetical flood event accessed by routing a known stage hydrograph for a channel reach having a rectangular cross section which fully penetrates the adjoining aquifer given by Zitta and Wiggert (Water Resour Res 7:1341–1345, 1971). A simplified mathematical approach, based on Darcy’s law, has been presented here for the solution of groundwater flow equations. The results obtained from the adopted procedure are also compared with the solution proposed by Zitta and Wiggert in 1971. The NSE and RMSE (m3/s) estimate assessed for the simulated hydrographs using the proposed methodology with respect to the procedure adopted by Zitta and Wiggert (Water Resour Res 7:1341–1345, 1971) is 0.9983 and 0.8544, respectively. Therefore, the use of Simpson’s (3/8)-rule is not suggestible due to its complicated calculation and its sensitivity, and it is better to use the proposed simplified approach for the evaluation of lateral flow.

Impacts of Climate on Renewable Groundwater Resources and/or Stream–Aquifer Interactions

The evaluation of aquifer recharge is essential to make a quantitative evaluation of renewable groundwater resources required to implement proper water policies aimed at maintaining stream–aquifer interactions, guaranteeing water supply to human activities, and preserving groundwater-dependent ecosystems at different spatial and temporal scales and climate conditions [...]

Effects of Baekje Weir Operation on the Stream–Aquifer Interaction in the Geum River Basin, South Korea

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.