Multi-aquifer System Research Articles

A multidisciplinary approach using hydrogeochemistry, δ15NNO3 isotopes, land use, and statistical tools in evaluating nitrate pollution sources and biochemical processes in Costa Rican volcanic aquifers

Nitrate pollution threatens the Barva and Colima multi-aquifer system, the primary drinking water source in the Greater Metropolitan Area of Costa Rica. In addressing nitrate contamination dynamics, this study proposes an integrated approach by combining multivariate statistical analyses, hydrochemical parameters, sewage discharge, and regional land-use and land-cover patterns to assess the extent and degree of contamination, dominant biogeochemical processes, and refine the interpretation of nitrate sources previously derived solely from δ15NNO3 information. Over seven years (2015–2022), 714 groundwater samples from 43 sites were analyzed for nitrate and major ions, including two sampling campaigns for dissolved organic and inorganic carbon, nitrite, ammonium, FeTotal, MnTotal, and δ15NNO3 analyses. The findings presented elevated nitrate concentrations in urban and agricultural/urban areas, surpassing the Maximum Concentration Levels on several occasions, and oxidizing conditions favoring mineralization and nitrification processes in unconfined Barva and locally confined Upper Colima/Lower Colima aquifers. Similar nitrate contents and spatial patterns in agricultural and urban zones in the shallow Barva aquifer suggest comparable contributions from nitrogen fertilizers and urban wastewaters despite the gradual increase in urban land cover and the reduction of agricultural areas. Isotopic analyses and dissolved organic carbon (DOC) indicate a shift in nitrate sources from agricultural to urban areas in both Barva and Colima aquifers. Principal Component and Hierarchical Cluster Analyses link land use, nitrate sources, and water quality. Three distinct sample clusters aligned with forest/grassland, agricultural/urban, and urban land use, emphasizing the impact of anthropogenic activities on groundwater quality, even in the deeper Colima aquifers. The study challenges nitrate isotope mixing models, enhancing accuracy in identifying pollution sources and assessing the spatial extent of contamination by incorporating DOC and other hydrochemical parameters. Similar outcomes, with and without the use of nitrate isotopes, reinforce the usefulness of the integrated approach, providing a practical and cost-effective alternative.

Controlling Arsenic Cross-contamination in Multi-aquifer System of Gangetic Flood Plain Through Optimal Well Spacing Based on Aquifer Response Modelling—A Case Study from Buxar District and Neighbouring Areas, Bihar, India

Controlling Arsenic Cross-contamination in Multi-aquifer System of Gangetic Flood Plain Through Optimal Well Spacing Based on Aquifer Response Modelling—A Case Study from Buxar District and Neighbouring Areas, Bihar, India

Effect of Stratum Distribution on Deep Circular Excavation with Dewatering Above a Multi-Aquifer System by Hydro-Mechanical Coupled Numerical Analysis

Effect of Stratum Distribution on Deep Circular Excavation with Dewatering Above a Multi-Aquifer System by Hydro-Mechanical Coupled Numerical Analysis

Effects of deep coal mining on groundwater hydrodynamic and hydrochemical processes in a multi-aquifer system: Insights from a long-term study of mining areas in ecologically fragile western China

The groundwater hydrodynamic and hydrochemical process of the multi-aquifer system will experience complicated and serious influence under deep coal mining disturbance. There is relatively little research that has integrated hydrodynamic and hydrochemical properties of groundwater to investigate the spatiotemporal distribution characteristics and evolution patterns of hydrogeochemistry and hydrodynamic information in deep multi-aquifer systems. The study of the groundwater hydrodynamic and hydrochemical spatiotemporal coupling response of multi-aquifer systems under the deep and special thick coal seam mining-motivated effect in ecologically fragile western mining areas is of great significance for the safe mining of coal resources and ecological environment protection. In this research, the hydrochemical analysis data composed of 218 groundwater samples from Tangjiahui coalfield, Northwest China with 1526 measurements and a 6-year (2016–2021) sampling period were collected for studying the hydrogeochemical spatiotemporal evolution process and governing mechanism of the multi-aquifer system using hierarchical cluster analysis, ion-ratio method, saturation index and multidimensional statistical analysis. Additionally, wavelet analysis and cross-wavelet coherence analysis were implemented to quantitatively recognize the spatiotemporal variation characteristics of hydrodynamic information and analyze the coherence relationships between time series. The results demonstrate that the hydrochemical characteristics exhibit significant spatial differences, while the temporal variation of hydrochemical characteristics in the Permian Shanxi Formation fractured sandstone aquifer (PSFFA), mine water (MW), and Ordovician karst limestone aquifer (OKA) is not significant. The water-rock interaction is the predominant control mechanism for the spatial evolution of hydrogeochemistry in the research area. Moreover, the large-scale mining of deep coal seams controls the type and degree of water-rock interactions by damaging the structure of aquifers and altering the hydrodynamic conditions of groundwater. The period from 2016 to 2021 exhibits multi-time scale characteristics in time series of precipitation, mine water discharge, and the water level of PSFFA and OKA. The mine water discharge has a positive correlation with the water level of PSFFA and OKA, whereas the significant period of precipitation and the water level of PSFFA coherence is not obvious. The research findings not only provide in-depth insights to protect the groundwater resources in water-shortage mining areas but also promote the secure mining of deep coal resources.

Why pile-supported building settled continuously after water level was stabilized during dewatering: Clues from interaction between pile and multi aquifers

Dewatering in a multi-layered aquifer-aquitard system often causes groundwater drawdowns in multiple aquifers, which together lead to obvious settlement of adjacent pile-supported building. This paper documents an in-situ pumping test conducted in a multi-aquifer system. It indicates that an adjacent pile-supported building settled continuously after water level was stabilized. To clarify the possible reasons for this phenomenon, a series of numerical models were established, validated and employed to explore the load transfer behaviour between pile and multi-aquifers during different dewatering conditions. Results indicate that the appearances of several aquitards in the multi-aquifer system significantly block the hydraulic connection between different aquifers, leading to non-synchronized developments of groundwater drawdown and pile shaft resistance at different soil layers during pit dewatering, which eventually causes the lagging settlement of the building. In practical pit dewatering in multi-aquifer system, engineers should appropriately increase the monitoring time for the deformation of adjacent pile-supported buildings for avoiding missing the maximum settlement.

Anthropogenic processes drive spatiotemporal variability of sulfate in groundwater from a multi-aquifer system: Dilution caused by mine drainage

The water quality evolution of surface and groundwater caused by mining activities and mine drainage is a grave public concern worldwide. To explore the effect of mine drainage on sulfate evolution, a multi-aquifer system in a typical coal mine in Northwest China was investigated using multi-isotopes (δ34SSO4, δ18OSO4, δD, and δ18Owater) and Positive Matrix Factorization (PMF) model. Before mining, the Jurassic aquifer was dominated by gypsum dissolution, accompanied by cation exchange and bacterial sulfate reduction, and the phreatic aquifers and surface water were dominated by carbonate dissolution. Significant increase in sulfate in phreatic aquifers due to mine drainage during the early stages of coal mining. However, in contrast to common mining activities that result in sulfate contamination from pyrite oxidation, mine drainage in this mining area resulted in accelerated groundwater flow and enhanced hydraulic connections between the phreatic and confined aquifers. Dilution caused by the altered groundwater flow system controlled the evolution of sulphate, leading to different degrees of sulfate decrease in all aquifers and surface water. As the hydrogeochemical characteristic of Jurassic aquifer evolved toward phreatic aquifer, this factor should be considered to avoid misjudgment in determining the source of mine water intrusion. The study reveals the hydrogeochemical evolution induced by mine drainage, which could benefit to the management of groundwater resources in mining areas.

Formulation of Generalized Hillslope Leakage-Dependent Model for Groundwater Flow in N-Aquifer System within a Sedimentary Basin

In this study, the recently derived Hillslope Leakage-dependent (HL-D) models for groundwater flow in leaky three-aquifer system have been generalized to obtain Generalized Hillslope Leakage-dependent, GHL-D equation that model groundwater flow in leaky n-aquifer system. This generalization extends the capability of Hillslope Leakage-dependent (HL-D) equations to modeling groundwater flow in any number of aquifers (n-aquifer system) of all configurations within a sedimentary basin. The formulated GHL-D Model was tested on some aquifer types and the results have shown that it can be used to obtain groundwater flow models for both hillslope (sloping) and horizontal single aquifer (unconfined and confined) as well as for multi-aquifer system containing any number of aquifers within a sedimentary basin. This unique feature of GHL-D equation to model most aquifers types and configurations makes it a more elegant groundwater flow modeling tool with potentials for wider applications than most of the existing groundwater flow models. The GHL-D Model, when use for simulations of groundwater flow in single or multi-aquifer system, will have the capability of giving better understanding of the groundwater flow dynamics in such systems. This is important because most of the sedimentary basins of the world are multi-aquifer in nature and accurate knowledge of groundwater flow within them is important to geoscientists in determining long time yield and water sustainability in such geological structures

Mathematical modelling for groundwater management for multilayers aquifers (Erbil basin)

This study addresses the pressing issues of groundwater depletion and drought problems in the Erbil basin, a vital resource region in the Middle East. Focused on an area of strategic importance due to its large size and critical water resources, the study employs the Groundwater Modeling System (GMS) software to create a detailed 3D hydrogeological model based on extensive borehole data. With over 240 boreholes analyzed, the study strategically selects 70 accurate wells drilled by the Groundwater Directorate. The construction of the 3D stratigraphic models for the Erbil basin relies on three main historical data including boreholes, geological formations and a comprehensive approach, incorporating deep well logging data and the definition of distinct geological layers. By discerning the presence of previous and impervious layers, the model effectively categorizes the aquifer types within the Erbil basin. The aquifer system is delineated based on stratigraphic units, designating materials with high conductivity (silt, sand, and gravel) as aquifers and clay (or claystone) as aquitards. A 3D steady-state groundwater flow model is successfully executed, employing PEST pilot point for automated parameter estimation. The model, validated with a coefficient of determination (R2) of 0.9998, reveals hydraulic conductivity values ranging from 0.000980705 to 100 m/day and a recharge value of 0.000976443 m/day. The study classifies Erbil's aquifer types as unconfined, confined, and semi-confined, providing a valuable foundation for groundwater management. The primary objective of this study is to construct a calibrated numerical groundwater model for the multi-aquifer system in the Erbil basin. The model aims to serve as a robust tool for analyzing the sustainability of diverse groundwater infrastructure development strategies within the region. The Erbil basin poses unique challenges for groundwater modeling, marked by a scarcity of critical data such as monitoring well information, pumping rates, recharge rates, and flow budgets. In response to these limitations, the study adopts an innovative approach by integrating in situ data with earth observation data. The integration of these datasets seeks to overcome data constraints and enhance the accuracy of the groundwater model. By achieving calibration and validation of the numerical model, this research strives to provide a valuable resource for decision-makers, planners, and stakeholders involved in groundwater management in the Erbil basin. Ultimately, the study aims to contribute to the development of sustainable and effective strategies for the utilization and preservation of groundwater resources in this vital region and also to enhance practical management strategies for the Erbil groundwater basin, ensuring sustainable utilization of the crucial sub-surface water resources, an objective successfully achieved through this research.

Joint interpretation and modeling of potential field data for mapping groundwater potential zones around Debrecen area, Eastern Hungary

The Debrecen area, as part of the Great Hungarian Plain (GHP), is associated with a multi-aquifer system that is overly exploited to fulfill the development plans. This research aims to jointly interpret and model gravity and magnetic data to map the subsurface geology and structures that govern groundwater occurrence. Various potential field techniques, including spectral analysis, anomaly derivatives, analytical signal, and Euler deconvolution were employed to map the distribution and depth of the buried geological structures. The combination of the potential field techniques enabled the construction of a detailed lineament map, providing valuable insights into the distribution of the subsurface structural features. It was indicated that the main structural trend is NW–SE and NE–SW, that coincides with the main structural trends in Hungary. Subsequently, a lineament density map is derived, indicating that the eastern, central, and northwestern parts of the area form the most promising zones for groundwater prospection. The joint inversion of gravity and magnetic data has further enhanced the understanding of subsurface geology. The depth to the basement rock varied between 1.18 and 2.2 km. The highest depth to the basement meets with thick sedimentary sequences bounded by normal faults forming graben and horst structures. Moreover, the distribution of these sediments is investigated using lithological logs indicating the thickness of the main hydrostratigraphic units in the Debrecen area. These units include Nagyalföld Aquifer, Algyő Aquitard, Endrőd Aquitard, and Miocene Badenian Aquifer units, which mainly consist of sand, silt, marl, and gravel. The recent study demonstrated the effectiveness of the joint interpretation in enhancing the knowledge of lithology and geological structures. However, a detailed geophysical survey is recommended to characterize the hydrostratigraphic units in the Debrecen area.

Comparison of different statistical approaches to assess spring potential mapping in a multi-aquifer system: a case study of Kurdistan Region, Iraq

Comparison of different statistical approaches to assess spring potential mapping in a multi-aquifer system: a case study of Kurdistan Region, Iraq

Steady-state simulation of groundwater flow in Khartoum state, Sudan

AbstractThe multi-aquifer system of the Nubian aquifer in central Sudan hydrogeological system was simulated using a three-dimensional steady-state model. The goal of the study is to detect the effect of pumping on the groundwater flow and thus, the aquifer productivity. The conceptual model of the study area was built based on the available geological and hydrogeological data guided by geophysical survey. Processing MODFLOW numerical code was used to calculate the hydraulic head and water balance under the existing boundary conditions. The model accurately simulated the hydraulic head with a determination coefficient of 0.88. The calibrated model indicated that the change in storage is 0.56 m3/day indicating the study area constitutes highly productive zone and is recommended for groundwater developments.

Importance of Aquitard Response Time for Groundwater Management in Multi-Aquifer Systems Subject to Land Subsidence

Groundwater management models have been widely applied to obtain optimal pumping strategies for land subsidence control, but most of them do not explicitly incorporate land subsidence variables (such as cumulative settlement and land subsidence rates) within the model constraints and neglect the transient effect due to aquitard storage. Here, three operating scenarios of a hypothetical multi-aquifer system, which include a highly compressible aquitard, were implemented with the aim of evaluating land subsidence and identifying management schemes with the support of an optimization model for groundwater management. In a 50-year management period, maximizing pumping while restricting drawdown to 10 m after year 25 stabilizes groundwater levels within the aquifer, but land subsidence continues to reach 4.8 m at year 50. The effect of reducing pumping rates and how early in the management period this is implemented is also analyzed. Restricting the pumping rate as early as year 6 leads to reduced land subsidence at year 50 by 17%. If pumping reduction is delayed, larger land subsidence rates occurred in the system (7.9, 8.3 and 9.6 cm/year in the tested cases); however, if the total settlement is evaluated as a proportion of the thickness of the aquitard, values of the order of 10% are presented. Our results highlight the importance of timely decisions for groundwater management based on the response time of the aquitards in multi-aquifer systems.

Hydrogeological and water quality analysis of thermal springs in the Guelma region of North-Eastern Algeria: A study using hydrochemical, statistical, and isotopic approaches

This study aimed to investigate the hydrogeological features of aquifers in the Guelma Basin using hydrochemical, statistical, and isotopic analyses. The hydrochemical facies of phreatic waters were determined by analyzing 13 parameters of 14 water samples, and correlations between mineralization and contributing elements were identified through statistical analysis. Isotopic analysis was utilized to establish the groundwater's origin. The results showed that water in the Guelma Basin is generally hard, with varying levels of mineralization ranging from significant to excessive. Water quality worsens progressively as it flows in the direction of groundwater flow, particularly in the post-nappe domain due to water/rock interaction. Furthermore, the hydrochemical facies of phreatic waters differed based on their location, with calcium bicarbonates in the upstream and calcium chlorides in the downstream. Through statistical analysis, the study found that mineralization is positively correlated with elements contributing to mineralization, such as Na+ and Cl-. Electrical conductivity (CE) and Residual Salt (RS) were also positively correlated with these ions. Isotopic analysis revealed that the groundwater in the area has an old origin, and the δ2H and δ18O relationship identified mixing effects in the multi-aquifer system. Additionally, the upward movement of thermal water from deep to shallow aquifers is likely due to the abundance of fractures and faults in the research area. This study provides valuable insights into the hydrogeological characteristics of aquifers in the Guelma Basin and can inform future planning related to water, agriculture, or industry in the region. By using hydrochemical, statistical, and isotopic approaches, the researchers were able to determine the origin and movement of groundwater in the area, which can be useful for future decision-making. Overall, the study highlights the importance of understanding the hydrogeological characteristics of aquifers to make informed decisions regarding water management and resource utilization.

Geochemical and isotopic tracers to define the aquifer’s vulnerability: the case study of the alluvial multi-aquifer system of the Friulian plain

The Friuli-Venezia Giulia Region (north of Italy) is characterized by the presence of high-quality freshwater resources which benefit local citizens, animals, environmental habitats, and also agriculture and production activities. Waters from wells, canal, and wastewater selected in the Fiume Veneto area, through a detailed lithological modeling, were sampled and analyzed to characterize them from a geochemical point of view. The chemical and isotopic characterization made it possible to establish provenance, and the average age of water used, making available the estimation of the relationships between recharge capacity and water use in the Fiume Vento area. The focus of this study is to define the average age of the resources based on the time required for the recharge contributions to compensate the losses induced by exploitation. The results made it possible to support the plans for a water balance using the provenance and average age of water sources for the protection of water reserves formed by the multi-aquifer system of the high and medium Friuli plain. The methodology applied has followed the legislation of the water directive considering the overexploitation due to unauthorized withdrawals of the sampling area.

Hydrogeochemical and Stable Isotope Data of the Groundwater of a Multi-Aquifer System in the Maknessy Basin (Mediterranean Area, Central Tunisia)

The Maknessy plain in central Tunisia is one of the most important agricultural basins in Tunisia. Given the semi-arid climate conditions, the irrigation of cultivated crops relies principally on the abstraction from groundwater resources. The assessment of the quality of the used water for agricultural purposes is crucial for safe production. Thus, the objective of this work is to assess the physicochemical quality of the irrigation water resources in this catchment area using a combined chemical, isotopic, and statistical approach. The waters analyzed are represented by two types of groundwater, mainly calcium hyper chloride and calcium sulfate. A multivariate statistical analysis (PCA and HCA) and a geochemical approach have been applied to study water quality as a function of chemical parameters, showing that the EC and TDS are the parameters influencing water quality. The stable isotopic compositions of the sampled waters range from −7.53 to −4.90% vs. VSMOW and from −53.6 to −32.2% vs. VSMOW for δ18O and δ2H; they show the exchange between groundwater and rock and the evaporation effect. The isotopic data form three groups such as recent water, paleowater, and mixing water indicate the evaporation effect and interaction of the groundwater, and confirm that this aquifer has been recharged by current rainwater. So, these aquifers were recharged by precipitation derived from a mixture of cloud masses from the Atlantic Ocean and the Mediterranean Sea. The findings of this research are of important relevance for effective water resources management in this agro-based region. Indeed, the increased exploitation of these resources will induce a continuous reduction in the available resources and progressive degradation of the used water quality that may adversely impact the safe agricultural production and the economic resilience of the local population.

Discriminant model and hydrogeochemical processes for characterizing preferential flow paths in four interconnected volcanic aquifers in Costa Rica

The volcanic Barva and Colima multiaquifer system is crucial for the drinking water supply of about 1.7 million people, about 30% of the population in Costa Rica. The complexity of this system and the simultaneous occurrence of anthropogenic and natural processes complicate the understanding of hydrochemical and hydrogeological dynamics, both essential for groundwater protection. This research aimed to develop a model for the discrimination of groundwaters according to the main withdrawn aquifer and flow path, assess interaquifer connections, and evaluate the main hydrochemical processes governing water quality. Samples (571) from 38 sampling sites, collected quarterly from 2016 to 2020, were analyzed for nitrate, major ions, and silica. Principal component analysis and discriminant analysis exhibited and validated sample grouping according to the primary aquifer system captured, i.e., Upper Barva, Lower Barva, Upper Colima, and Lower Colima, and the occurrence of two flow paths within the Lower Barva and Upper Colima aquifers. Hydrochemical and statistical analyses showed resilience to seasonal chemical variation in deeper aquifers and also three groundwater mixing processes. Lower Barva groundwater enriches in bicarbonate, magnesium, calcium, sodium, and silica, mainly due to weathering of mafic andesitic-basaltic lavas. The Upper and Lower Colima showed higher silica and major ion content, except for calcium, indicating longer residence times, dissolution from felsic andesitic minerals, and calcium adsorption by normal ion exchange. Weathering of aluminosilicates is the primary process governing groundwater quality in the four studied aquifers, whereas cation exchange, interaquifer leakage, and anthropogenic processes might modify the groundwater chemistry.

Groundwater Circulation and Origin of Salinity in a Multi-aquifer System: The Gohar-Zamin Mining Area, Iran

Groundwater Circulation and Origin of Salinity in a Multi-aquifer System: The Gohar-Zamin Mining Area, Iran

Hydrogeochemical evolution induced by long-term mining activities in a multi-aquifer system in the mining area

The hydrogeochemical evolution of groundwater is related to and affected by long-term mining activities, which may deteriorate the quality of groundwater. The Fengfeng mine in Handan, North China has a 30-y history of coal mining with long-term mining activities and complex geological conditions, resulting in a complex hydrogeochemical environment in the mining region. In this study, the hydrogeochemical evolution mechanism of groundwater in a multi-aquifer system in the Fengfeng Mining Area was investigated using machine learning (self-organizing maps combined with K-means clustering) and sulfur and oxygen isotopes (δ34SSO4 and δ18OSO4). The hydrogeochemical characteristics of different aquifers in the mining area changed to different degrees after mining compared with the characteristics before mining. The spatiotemporal variations in groundwater components were found to be controlled by pyrite oxidation, gypsum dissolution, and carbonate dissolution, which are affected by mining activities. Pyrite oxidation primarily occurred in the Carboniferous thin-layer limestone aquifer (CLA) and Permian sandstone aquifer (PSA). The hydrogeochemical evolution in the Ordovician limestone aquifer (OLA), the main aquifer in the study area, was affected by leakage recharge from CLA and PSA caused by mining activities. The results showed that owing to the effects of long-term mining, the altered groundwater flow system affected the evolution of groundwater components in each aquifer, particularly the sulfate concentration. This study reveals a distinct hydrogeochemical evolution induced by mining activities, which can provide a basis for groundwater resource management in mining areas.

Hydrogeochemical and isotopic investigation of the multilayer aquifer system: a case study of the Quaternary and the Campanian aquifers of the Mateur plain, Northern Tunisia

Abstract The Mateur multi-aquifer system, consisting of a Quaternary alluvial aquifer and a Campanian limestone aquifer, is one of the most significant aquifer systems in northern Tunisia, providing domestic and agricultural water supply for the entire Mateur region. The present study aims to unveil the various factors and mechanisms controlling the groundwater chemistry of such a system. Indeed, integrated hydrogeochemical and isotopic approaches are used herein to identify the alluvial and limestone aquifer waters mixing and evolution in the Mateur region. Results show that despite the difference in aquifer lithology, there is little difference in the major ion geochemistry and stable isotope ratios of groundwater within the Mateur plain. Waters from the Quaternary alluvial aquifer are classified into two predominant facies: mixed facies (Ca–Na–SO4–Cl and Ca–Na–HCO3–Cl) and Na–Cl facies. Similarly, waters from the limestone aquifer have also mixed facies (Ca–Na–SO4–Cl) and sodium chloride facies (NaCl). Groundwater δ18O and δ2H values show more homogeneous values along the groundwater flow direction, indicating inter-aquifer mixing processes. Tritium contents of the Campanian aquifer are lower than those of the Quaternary aquifer, indicating a relatively older age or mixture with recent waters. This validates a concept of the hydraulic continuity between the Quaternary aquifer and the Campanian aquifer which is consistent with the geochemical analytical results.

Hyporheic zone geochemistry of a multi-aquifer system used for managed aquifer recharge in Beijing, China

Hyporheic groundwater geochemistry evolution depends on the interactions of surface water and groundwater (SW–GW). Hydrodynamic variations driven by the long-term managed aquifer recharge (MAR) practice could change hyporheic geochemical processes, which requires a better understanding for groundwater management. In this work, a geochemical survey was conducted in a multi-aquifer MAR system. The results showed great impact of the MAR practice on the hydrodynamics and major ion chemistry of groundwater in the hyporheic zone compared to natural recharge. Besides, related geochemical processes including rock weathering and ion exchange showed increased effect on hyporheic hydrochemistry with aquifer depth, depending on hydrogeological conditions in addition to river water infiltration. Combined with hydrochemical indicators and the end-member mixing model, the relative contribution of precipitation to groundwater was estimated to be 5% for the 30-m aquifer, 16% for the 50-m aquifer, and 64% for the 80-m aquifer. However, precipitation made small contributions (<5%) to the major ions of groundwater regardless of depth. Conversely, the relative contributions of river water infiltration decreased with aquifer depth (95%→84%→36%), and its proportional contributions to major ions showed a similar trend (90%→84%→39%), which suggests reduced SW–GW interaction intensity with depth in the hyporheic zone. The major ion compositions of hyporheic groundwater tend towards river water after the long-term MAR practice, reflecting comprehensive effect of mixing and related geochemical processes. This study demonstrates the relevance of detailed studies at regional scale to understand anthropogenic effects from projects such as MAR on groundwater geochemistry especially in multi-aquifer systems.