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Groundwater models are valuable tools to quantify the response of groundwater level to hydrological stresses induced by climate variability and groundwater extraction. These models strive for sustainable groundwater management by balancing recharge, discharge, and natural processes, with groundwater level serving as a critical response variable. While traditional numerical models are labour-intensive, machine learning and deep learning offer a data-driven alternative, learning from historical data to predict groundwater level variations. The groundwater level in wells is typically recorded as continuous groundwater level time series data and is essential for implementing managed aquifer recharge within a particular region. Machine learning and deep learning are essential tools to generate a data-driven approach to modeling an area, and there is a need to understand if they are the most suitable tools to improve model prediction. To address this objective, the study evaluates two machine learning algorithms - Random Forest (RF) and Support Vector Machine (SVM); and two deep learning algorithms - Simple Recurrent Neural Network (SimpleRNN) and Long Short-Term Memory (LSTM) for modeling groundwater level changes in the West Coast Aquifer System of South Africa. Analysis of regression error metrics on the test dataset revealed that SVM outperformed the other models in terms of the root mean square error, whereas random forest had the best performance in terms of the MAE. In the accuracy analysis of predicted groundwater levels, SVM achieved the highest accuracy with an MAE of 0.356 m and an RMSE of 0.372 m. The study concludes that machine learning and deep learning are effective tools for improved modeling and prediction of groundwater level. Further research can incorporate more detailed geologic information of the study area for enhanced interpretation. [ABSTRACT FROM AUTHOR]

Anthropogenic climate change leads to increased precipitation intensity and exacerbated droughts in California, challenging the reliability and drought resiliency of water supply. Storing floodwater underground via managed aquifer recharge can mitigate these effects through direct infiltration or streambed infiltration. Seasonally dry streams (arroyos) already play an important part in managing groundwater recharge to the Livermore basin (CA). Understanding how, when and where stormwater and arroyo water infiltrate is critical to effectively utilise this strategy. To track water from recent storms (water year 2022–2023, WY23) into the Livermore Valley Groundwater Basin, we analysed stable water isotopes (δ18O and δ2H) in combination with naturally occurring radioactive isotopic tracers, sulphur‐35 (35S, t½ = 87 days) and tritium (3H, t½ = 12.3 years). By comparing measurements of δ18O, 35S and 3H in arroyos to precipitation and groundwater, we classified the relative age and identified source of recharge to 16 wells near two arroyos. Two wells contained water with recent recharge (from WY23) from local precipitation. One well had recent recharge from variable (precipitation and imported water) sources. One well contained imported water recharge. Three wells contained water from mixed recent and older (pre‐WY23) waters, from local precipitation sources. Two wells contained recent recharge from local mine settling ponds. Seven wells had older recharge from local precipitation sources. This combination of isotopes allows us to delineate where local and imported water recharges in this highly managed basin and identify locations where managed aquifer recharge is contributing to rapid groundwater infiltration. Our combined interpretation of isotopic water ages and sources in the context of land use shows that local infiltration of precipitation in open spaces is an important recharge mechanism, in addition to the managed arroyo recharge. A broader familiarity with 35S will enable more extensive research on the infiltration of urban floodwaters. [ABSTRACT FROM AUTHOR]

Managed aquifer recharge (MAR) is increasingly being adopted worldwide to mitigate groundwater depletion and ensure the sustainability of water resources. Rainwater harvesting (RWH)-MAR can augment aquifer storage and reduce flood damage in rural areas with dense greenhouse facilities. This study has assessed the feasibility of greenhouse RWH-MAR in Namwon agricultural areas in the southern part of Jeju Island, South Korea, by considering the injection rate and location of MAR using a numerical model. The model results showed that groundwater level increases were directly related to the infiltration rate, although spatial differences in head rise were observed owing to the spatial variability of hydraulic conductivity. In addition, installing the RWH-MAR in highland areas (>100 masl) enhanced the water level rise when compared to the expected values, indicating that a higher hydraulic gradient and thick unsaturated zone facilitated more effective MAR outcomes than in lowland areas. To optimize the contribution of source water to the agricultural water demand, placing the RWH-MAR near the pumping well improved the availability of injected rainwater to agricultural wells. This study highlights the importance of designing RWH-MAR schemes considering MAR objectives and the topographic and hydrogeological characteristics of the site. [ABSTRACT FROM AUTHOR]

Managed aquifer recharge (MAR) is a strategy within water resources management. However, issues related to clogging have hindered its implementation. The change in permeability of the medium is significantly influenced not only by the macroscopic characteristics of infiltration sand, such as heterogeneity and anisotropy, but also by its microstructural features, including pore structure, morphology and connectivity. Nevertheless, the interactions between fluid flow, particle migration and changes in permeability remain unclear. This study investigates the pore‐scale response mechanisms between fluid flow and pore clogging using a non‐destructive x‐ray computed tomography approach. Our findings indicate that the decrease in permeability due to particle deposition occurs in stages, with particles preferentially accumulating in irregularly shaped pores. The changes in the permeability of the sand column exhibit a negative correlation with alterations in shape factor and tortuosity, while showing a positive correlation with the fractal dimension. As pores become clogged with particles, the increase in tortuosity leads to a longer flow path. Once the sharp edges of the irregular pores are filled with particles, the pore space becomes smoother and more uniform, and the fractal dimension of the pores gradually decreases with further clogging. Based on numerical modelling of particle movement and the clogging process in porous media, it was determined that pressure is greatest in clogged pores. When this pressure reaches a certain threshold, the particles that were previously trapped in the pores are flushed out, leading to uneven changes in normalised hydraulic conductivity and normalised concentration at the outlet. If the pressure is insufficient to dislodge the clogging particles, the water flow path is compelled to change, resulting in a gradual stabilisation of the clogging. [ABSTRACT FROM AUTHOR]

An intensively irrigated area in southern part of Punjab Province, Pakistan, has been selected by the Punjab Irrigation Department (PID) to implement a Managed Aquifer Recharge (MAR) project. This project involves diverting floodwater from the Islam Headwork on Sutlej River into the abandoned Mailsi Canal. Utilizing various structures such as depressions, abandoned canals, flood channels, open fields, and deserts for MAR can reduce the flood intensity while recharging aquifer and wetlands. The study area, known for its fertile lands and serving as a food basket for the Punjab Province, is experiencing groundwater depletion at the rate of 0.30 m to 0.70 m per year, significantly increasing pumping costs. This study aims to evaluate the suitability of the sites for the MAR project and assess the storage capacity of the aquifer for floodwater retention. Historical groundwater level data from 25 observation wells across an area of 1,522 km2 were analysed, with the study area divided in to 25 polygons using ArcMap10.6 software. Specific yield method was employed to assess the available storage capacity of the aquifer. Results indicate that the site is suitable for MAR and has the potential to store approximately 1.88 km3 of floodwater as of 2020, thereby reducing flood intensity and enhancing eco-hydrogeological conditions. MAR is identified as a Nature-Based Solution (NBS) for both flood mitigation and groundwater sustainability.

The Mississippi Embayment aquifer is one of the largest alluvial groundwater aquifers in the United States. It is being excessively used, located along the lower Mississippi River covering approximately 202,019 km2 (78,000 square miles). Annual average groundwater depletion in the aquifer has been estimated at 5.18 billion cubic meters (Gm3) (4.2 million acre-feet) in 1981–2000. However, since 2000, annual groundwater depletion has increased abruptly to 8 Gm3 (2001–2008). In recent years, multi-state efforts have been initiated to improve the Mississippi Embayment aquifer sustainability. One management strategy of interest for preserving groundwater resources is managed aquifer recharge (MAR). In this study, we evaluate the impact of different MAR scenarios on land and water use decisions and the overall groundwater system using an economic model able to assess profitability of crop and land use decisions coupled to the Mississippi Embayment Regional Aquifer Study (MERAS) hydrogeologic model. We run the coupled model for 60 years by considering the hydrologic conditions from the MERAS model for the years 2002–2007 and repeating them 10 times. We find MAR is not economically attractive when the water cost is greater than $0.05/m3. Groundwater storage is unlikely to improve when relying solely on MAR as groundwater management strategy but rather should be implemented jointly with other groundwater conservation policies.

This study focuses on detecting and mitigating soil salinization in four coastal areas of the Mekong Delta (Vietnam). Salinity patterns in the soils of the Mekong River Delta are not random but linked to land use practices and distance to the sea. We examine two quick yet reliable remote sensing-based techniques to detect the coastal aquaculture area and separate it from the inland freshwater farmland. These techniques can eventually be used to identify locations with an elevated risk of salinization in other coastal regions. Finally, we investigate a salinization mitigation solution based on creating a managed aquifer recharge system along the buffer zone that separates the coastal aquaculture area from the inland freshwater agriculture area. The implementation of an infiltration pond system is technically feasible in the Mekong Delta provided that hydrogeological characteristics, the fresh-saline interface position, and freshwater demands are considered. The transitional zone between freshwater agriculture and brackish water aquaculture in Bac Lieu, Soc Trang, Tra Vinh and Ben Tre provinces is optimal for implementing an aquifer recharge/freshwater barrier scheme. [ABSTRACT FROM AUTHOR]

Seawater intrusion (SWI) is threatening coastal aquifers and farmland productivity worldwide. Although this phenomenon naturally occurs in coastal areas, it is intensified by anthropogenic activities such as groundwater pumping and land reclamation that cause a lowering of the hydraulic head and land subsidence. Moreover, the consequences of climate change such as sea level rise, increase of the mean temperature and the shifting of rainfall events to tropical regimes, have strong negative effects on groundwater quality and agriculture. Countermeasures against SWI are needed to maintain agricultural productivity and protect the freshwater resources in coastal areas. In the low‐lying farmlands surrounding the southern Venice Lagoon, in northern Italy, SWI is exacerbated by land subsidence, the presence of sandy paleochannels connected to the lagoon subsurface, seawater encroachment into the river estuaries, the presence of fossil brine waters and peat deposits. This study provides a detailed hydrogeological and geochemical characterisation of an experimental agricultural field affected by SWI located in this area using a large dataset collected over the 4 years between 2019 and 2022. Furthermore, it presents the results of novel intervention established across the farmland in 2021 to mitigate saltwater contamination. This intervention involved a controlled discharge of freshwater supplied by a reclamation channel through a 200 m‐long drainpipe buried 1.5 m below the field surface along a well‐preserved sandy paleochannel. The interpretation of the collected data demonstrates that the freshwater recharge carried out in 2021 and 2022 effectively reduced the groundwater salinity along the paleochannel. Moreover, statistical analyses highlighted that a certain lateral spread of freshwater occurred too, although the variability of the monitored parameters in the sites located outside the sandy body was only partially explained by the drain activity. [ABSTRACT FROM AUTHOR]

Through the provision of drinking and agricultural irrigation water, groundwater resources fundamentally underpin the existence of modern human society across large regions of the world. Despite this, decades of unsustainable exploitation have led to acute degradation of groundwater quantity and quality, creating pressing challenges that society must address if we are to maintain viable access to this crucial resource for future generations. Taking stock of the current situation, in this contribution we begin by reviewing some of the major global groundwater resource pressures, before exploring a range of technological, engineering, societal and nature-based solutions to address these challenges. We look at examples of emerging groundwater resource threats and potential innovative solutions to tackle them, before concluding with a forward look at future research opportunities that can ultimately enhance our management of this vital resource.

Managed aquifer recharge (MAR) can provide long-term storage of excess surface water for later use. While decades of research have focused on the physical processes of MAR and identifying suitable MAR locations, very little research has been done on how to consider competing factors and tradeoffs in siting MAR facilities. This study proposes the use of a simulation-optimization (SO) framework to map out a cost-effectiveness frontier for MAR by combining an evolutionary algorithm with two objective functions that seek to maximize groundwater storage gains while minimizing MAR cost. We present the theoretical framework along with a real-world application to California's Central Valley. The result of the SO framework is a Pareto front that allows identifying suitable MAR locations for different levels of groundwater storage gain and associated MAR project costs, so stakeholders can evaluate different choices based on cost, benefits, and tradeoffs of MAR sites. Application of the SO framework to the Central Valley shows groundwater can be recharged from high-magnitude (95th percentile) flows at a marginal cost of $57 to $110 million per km3. If the 10 percent largest flows are recharged the total groundwater storage gain would double and the marginal costs would drop to between $30 and $50 million per km3. If recharge water is sourced from outside local basins (e.g., the Sacramento-San Joaquin Delta), groundwater storage gain is approximately 25%–80% greater than can be achieved by recharging local flows, but the total cost is about 10%–15% higher because of additional lift cost.

More than two billion people and 40% of global agricultural production depend upon unsustainable groundwater extraction. Managed aquifer recharge (MAR), the practice of strategically recharging water to replenish subsurface storage, is an important subbasin scale practice for managing groundwater more sustainably. However, it is not yet reaching its full potential to counterbalance growing global groundwater demand. Agricultural managed aquifer recharge (Ag-MAR) is an emerging method for spreading large volume flows on agricultural lands and has capacity for widespread global implementation. Yet, knowledge gaps, synergies, and tradeoffs in Ag-MAR research still exist. We identify six key system considerations when implementing Ag-MAR: water source, soil and unsaturated zone processes, impact on groundwater, crop system suitability, climate change and impact on greenhouse gas emissions, and social and economic feasibility. We describe the present distribution, need for common terminology, and benefits of Ag-MAR including groundwater storage, increased environmental flows, and domestic wells support. We then outline major gaps, namely, water quality impacts, and crop health and yield. We showcase the multidisciplinary approach needed for communication and coordination of Ag-MAR programs with stakeholders and the public and provide a framework for implementation. Finally, we outline a vision for the path to Ag-MAR implementation. Ag-MAR is an important approach for achieving groundwater sustainability. However, it is one of many necessary solutions and does not offset the need for groundwater conservation.

MAR remains relatively underutilized in Central Asia despite its potential to address water scarcity issues, particularly those related to seasonal fluctuations in water availability. Thus, the objective of this study was to produce a map depicting the potential suitability of managed aquifer recharge (MAR) implementation in Kazakhstan. Employing a multi-criteria decision analysis framework, five distinct physical criteria were integrated and visualized within a Geographic Information System (GIS) to delineate the intrinsic potential for MAR. To demonstrate the practical utility of the generated map, it was applied to the Zhambyl region in Southern Kazakhstan, an area previously afflicted by water scarcity challenges. The intrinsic MAR potential map was overlaid with remote sensing data identifying potential water sources and water utilization patterns. This overlay facilitated the identification of priority areas with potential for further evaluation for MAR implementation. The map developed for Kazakhstan represents the first spatial representation of MAR potential within the region, serving to raise awareness regarding the feasibility of MAR application. It is anticipated that dissemination of this map will enhance understanding among water management professionals, potentially catalysing the integration of MAR methodologies into regional water management strategies. [ABSTRACT FROM AUTHOR]

Groundwater abstraction has increased tremendously due to population growth, urbanization, and industrial expansions. Managed Aquifer Recharge (MAR) has been a promising technique for increasing freshwater availability in response to water demand for different consumptions. This study aimed to identify suitable zones for MAR in the Diredawa catchment, eastern Ethiopia using multi-criteria decision analysis (MCDA). The seven parameters processed were soil texture, lithology, slope, land use and land cover, drainage density, transmissivity, and water quality (NO3). Each criterion was evaluated with analytical hierarchy process (AHP) and mapped by GIS. The sensitivity analysis was conducted using the map removal technique, and potential zones were validated using borehole yield data. The MAR suitability zones were assorted into very high, high, moderate, low, and very low suitability classes, representing 15.8%, 25.8%, 28.8%, 13.1%, and 16.3% areas. The MAR suitability mapping is highly affected by lithological variation. The alluvial sediment, upper sandstone, and fractured limestone with sandy loam soil texture are potential areas for implementing MAR. The highest potential MAR site is located in the western, southwestern, and northern parts of the catchment. This study will serve as a foundation for future site selection of MAR structures, aiming to enhance groundwater supply sources, improve groundwater quality, and manage urban flooding in the water-stressed and flood-prone Diredawa catchment. [ABSTRACT FROM AUTHOR]

Groundwater resources worldwide face significant challenges that require urgent implementation of sustainable measures for effective long-term management. Managed aquifer recharge (MAR) is regarded as one of the most promising management technologies to address the degradation of groundwater resources. However, in urban aquifers, locating suitable areas that are least vulnerable to contamination for MAR implementation is complex and challenging. Hence, the present study proposes a framework encapsulating the combined assessment of groundwater vulnerability and MAR site suitability analysis to pinpoint the most featured areas for installing drywells in Kayseri, Turkey. To extrapolate the vulnerable zones, not only the original DRASTIC but also its multi-criteria decision-making (MCDA)–based modified variants were evaluated with regard to different hydrochemical parameters using the area under the receiver operating characteristic (ROC) curve (AUC). Besides, the fuzzy analytical hierarchy process (FAHP) rationale was adopted to signify the importance level of criteria and the robustness of the framework was highlighted with sensitivity analysis. In addition, the decision layers and the attained vulnerability layer were combined using the weighted overlay (WOA). The findings indicate that the DRASTIC-SWARA correlates well with the arsenic (AUC = 0.856) and chloride (AUC = 0.648) and was adopted as the vulnerability model. Groundwater quality parameters such as chloride and sodium adsorption ratio, as well as the vadose zone thickness, were found to be the most significant decision parameters with importance levels of 16.75%, 14.51%, and 15.73%, respectively. Overall, 28.24% of the study area was unsuitable for recharge activities with high to very high vulnerability, while the remaining part was further prioritized into low to high suitability classes for MAR application. The proposed framework offers valuable tool to decision-makers for the delineation of favorable MAR sites with minimized susceptibility to contamination. [ABSTRACT FROM AUTHOR]

Drawing out too much groundwater, or overdrafting, is a serious problem in California. As a result, groundwater sustainability agencies are considering using recycled municipal wastewater to recharge aquifers. In our study, we employ suitability mapping and the models C2VSimFG and Ichnos to identify appropriate areas for managing aquifer recharge with recycled water in California’s Central Valley. The factors that influence suitability include soil properties, proximity to recycled water sources, and the residence time, or amount of time that recharged water spends underground. There are many suitable areas in the Central Valley that are immediately adjacent to water recycling facilities. However, adequate supply is an issue in most locations. Roughly half of the groundwater sustainability agencies in critically overdrafted basins of the Central Valley have enough potentially suitable locations to meet their recharge goals, but not all of them have access to enough recycled water. The methods demonstrated here can serve as tools for agencies considering using recycled water for aquifer recharging.

Given the substantial groundwater level declines in the Central Valley of California, there is an urgent need to supplement the recharge of the groundwater systems by implementing managed aquifer recharge. With approximately 170 km3 (140 million acre-feet) of available groundwater storage space, water deemed to be excess during wet years could be spread on the ground surface at selected locations allowing it to move downward to recharge the underlying aquifer system. Along the eastern edge of the Central Valley there are large paleovalleys that can act as fast paths expediting the downward movement of water. These paleovalleys, incised and then filled with coarse-grained materials—sand, gravel, cobbles—at the end of the last glacial period, are referred to as incised valley fill (IVF) deposits. An IVF deposit has been mapped at one location in the Kings River alluvial fan, with others proposed to exist in the fans of major rivers. If located, these deposits would be optimal sites for managed recharge. In this study, we assessed the use of a helicopter-deployed geophysical method to efficiently locate IVF deposits throughout the Central Valley. We acquired 542 line-kilometers of airborne electromagnetic (AEM) data in the Kings River alluvial fan, with dense line-spacing over the Kings River IVF deposit which had been mapped as ∼2 km wide, extending over 20 km into the Central Valley, from the ground surface to a depth of 30 m. The IVF deposit was unambiguously imaged in the AEM data as an extensive linear feature that was more electrically resistive than the surrounding materials due to the high percentage of coarse-grained sediments. This study provides the evidence to support the rapid adoption of the AEM method to locate IVF deposits along the eastern edge of the Central Valley. These deposits provide valuable natural infrastructure for recharging California’s groundwater.

Managed aquifer recharge (MAR) has been proposed as an innovative water storage method to manage variable water availability in Australian agricultural regions by combatting water shortage whilst addressing groundwater overuse and reducing large evaporative losses from surface storages. MAR innovations involve the recharge of water into aquifers and extraction when needed. However, their uptake has been limited as they are associated with large amounts of uncertainty. We present an argumentation approach to reason about the feasibility of MAR in the Coleambally Irrigation Area in the Murrumbidgee catchment. Three scenarios that focus on managed aquifer recharge and two competing surface water scenarios are developed for the case study area, as well as associated recommendations aimed at the key stakeholders who can initiate change. The approach and scenarios show potential, with future work involving the implementation of the recommendations and the application of the approach to another case study for further refinement. [ABSTRACT FROM AUTHOR]

Urbanization and climate change exacerbate groundwater overexploitation and urban flooding. The infiltration basin plays a significant role in protecting groundwater resources because it is a prevalent technology of managed aquifer recharge. It could also be utilized as a retention pond to mitigate city waterlogging. The goal of this study was to explore the offsets of artificial recharge on the extra runoff induced by urbanization and extreme storms via infiltration basins. To achieve this objective, a lumped infiltration basin module was developed and integrated into a semi-distributed hydrologic model. Then, the enhanced model was applied to an agriculture watershed with urban areas. Finally, the functionalities of the infiltration basins were evaluated under the scenarios of the predicted urbanization and extreme storms. The results demonstrated the capability of the infiltration basins to influence both artificial recharge and flood mitigation. To mitigate floods, especially peak flows, larger areas are needed for infiltration basins than for artificial recharge purposes only. Based on different demands, the intermittent regulation of infiltration basins according to different hydrologic periods is recommended. The offsets of artificial recharge on the extra surface runoff provide insight into the comprehensive preservation and management of surface water resources and groundwater resources. [ABSTRACT FROM AUTHOR]

Groundwater in the Nabogo Basin is threatened by increasing domestic and irrigation demands during the dry season, owing to climate change and overexploitation. Managed aquifer recharge (MAR) has therefore been proposed as a water management technique to augment groundwater resources. However, the success of MAR schemes depends on the selection of sites with suitable surface and subsurface properties to enhance the recharge rates. Thus, this study created spatial maps of the slope, drainage density, land use/cover, soil texture, transmissivity, groundwater depth, and aquifer thickness in the basin to create a suitability map. Analytical hierarchy process (AHP) with and without Monte Carlo (MC) simulation was used to create weights for each criterion based on seven expert opinions to assess their performance in dealing with uncertainties. The spatial maps and weights were then integrated to create a MAR suitability map. The results showed similar mean weights for AHP- and MC-aided simulations. However, MC-aided simulations narrowed the confidence interval and reduced the standard deviation of the AHP weights by 50–89%, thereby reducing the uncertainty and sensitivity of the weights. Furthermore, the suitability map showed that 38.8% (1124 km2), 39.2% (1136 km2), and 22% (637 km2) of the basin was suitable, less suitable, and unsuitable, respectively, for MAR applications. A receiver operating curve (ROC) value of 77.8% from the validation process indicated good model performance. This proves the effectiveness of MC simulations in reducing errors and uncertainty in the AHP. Therefore, it is a useful tool for mapping MAR suitability. [ABSTRACT FROM AUTHOR]

This paper presents an approach to estimate the effects of a managed recharge experiment in a multilayer aquifer characterized by the presence of perched water tables in the Medina del Campo groundwater body, Douro basin, central Spain. A numerical model was developed to evaluate the effect of artificial recharge on the shallow sector of a regional‐scale aquifer and on formerly active wetlands. The model was developed in the Visual MODFLOW Pro v.2011.1 environment in order to represent and analyse the regional impact of this artificial recharge event. Results suggest that the assumption of a single perched system may prove useful in regional contexts where data is limited. From a study site perspective, managed recharge is observed to increase shallow storage along the riverbanks, which is considered valuable for environmental purposes. However, downstream wetlands are unlikely to experience a significant recovery. Furthermore, only a small percentage of artificial recharge is expected to reach the deep regional aquifer. This method can be exported to settings characterized by the presence of perched aquifers and associated groundwater dependent ecosystems. [ABSTRACT FROM AUTHOR]

Study region: Flanders (Belgium) Study focus: Stormwater infiltration for managed aquifer recharge is increasingly recognized as a drought adaptation measure. Given the high degree of urbanization and imperviousness, stormwater infiltration has significant potential in Flanders (Belgium). This research presents a novel approach to quantify stormwater availability and its potential to enhance groundwater recharge. Stormwater volumes available for recharge are calculated based on the imperviousness level, yearly average precipitation volumes, and runoff coefficients. This study focuses on groundwater protection zones around drinking water wells to assess the role of increased infiltration for sustainable drinking water production. Calculated potential stormwater volumes for recharge are compared to natural groundwater recharge and pumping volumes for drinking water production to quantify the potential significance of stormwater infiltration for aquifer recharge. New hydrological insights for the region: Results show a high potential for stormwater infiltration in Flemish protection zones with an average of 17% (7%-33%) additional groundwater recharge from stormwater infiltration. Additionally, stormwater recharge could potentially compensate for 19% (8%-37%) of abstracted drinking water production from phreatic aquifers. Locally, higher groundwater recharge potentials were calculated, especially in protection zones around the city of Leuven. Therefore, stormwater harvesting for infiltration and groundwater recharge should be further encouraged throughout the region, with special attention to urban areas. However, further research is needed on stormwater quality to assess groundwater quality risks in this water quantity-quality balancing exercise.

Study Region: Southern Poland, Dunajec River catchment Study Focus: The study evaluated an eleven-year observation period of physicochemical parameters within a riverbank filtration (RBF) site located by the Dunajec River. A total of nine parameters (pH, electrical conductivity, sulphate, chloride, nitrate, manganese, water hardness, colour, turbidity) in both surface water and groundwater underwent statistical scrutiny. This analysis encompassed Spearman’s correlation, linear mixed-effects models and hypothesis testing. New Hydrological Insights for the Region: This study revealed that the Dunajec River constitutes a major factor in forming the exploited groundwater physicochemical composition. Statistically significant differences between two rows of wells were found, implying a more substantial RBF impact on the row closer to the Dunajec. However, the river’s influence on further wells was also highlighted. The RBF process in the study area was considered efficient since it maintained a stable groundwater physicochemical composition and provided sufficient water for exploitation over the years. Comprehending the interactions between the surface water and groundwater flow system is crucial to the well field sustainability, enabling water supply system optimisation and a more precise assessment of risks regarding groundwater contamination.

Groundwater is critical in countries such as Jordan, yet demand exceeds availability due to population expansion and arid conditions. The goal of this research is to address water scarcity and adapt to reduced rainfall by investigating the soil aquifer and evaluating the efficiency of managed aquifer recharge (MAR). The Wadi Araba Basin's alluvium aquifer is particularly important and contains a groundwater divide, with water flowing towards the Red Sea to the south and the Dead Sea to the north, as determined by rigorous modelling and scenario analysis. Precipitation infiltration is an important consideration in groundwater budget modelling. This study employs 12 monitoring wells to establish an acceptable relationship between estimated and observed water levels. Furthermore, the study creates a MAR suitability map, which evaluates eight potential MAR locations in the Wadi Araba region. According to forecasted scenarios, implementing MAR in conjunction with increased precipitation recharge has the potential to ameliorate the consequences of decreased rainfall in the model region. The plan aims to raise the water table in three areas by 1.96–3.12%, providing realistic solutions to enhance water availability and adapt to climate change. HIGHLIGHTS Groundwater plays a crucial role in addressing water scarcity.; Research in Wadi Araba Basin evaluating Managed Aquifer Recharge strategy to combat water scarcity.; The potential to raise the water table by 1.16% in specific areas.; Focusing on conductivity values to generate a calibration curve.; The level chart of the basin revealed ground water divided in alluvium aquifer water flows in two directions.;

Frequent and prolonged droughts challenge groundwater sustainability in California but managing aquifer recharge can help to partially offset groundwater overdraft. Here, we use managed aquifer recharge (MAR) to examine potential benefits of adding an artificial recharge facility downstream from California’s Lower American River Basin, in part to prepare for drought. We use a statewide hydroeconomic model, CALVIN, which integrates hydrology, the economics of water scarcity cost and operations, environmental flow requirements, and other operational constraints, and allocates water monthly to minimize total scarcity and operating costs. This study considers a recharge facility with unconstrained and constrained flows. The results show that adding a recharge facility increases groundwater storage, reduces groundwater overdraft, and increases hydropower without substantially impacting environmental flows. Further, artificial recharge adds economic benefits by (1) reducing the combined costs of water shortage and surface water storage and (2) by increasing hydropower revenue. This study provides a benchmark tool to evaluate the economic feasibility and water supply reliability impacts of artificial recharge in California.

Aquifers are increasingly stressed. Managed aquifer recharge provides a potential solution to mitigate this stress and provide sustainable groundwater resources. Subsurface properties are known to have a strong control on the infiltration rates that can be achieved. However, these properties are often highly heterogeneous and difficult to assess with conventional probing techniques. Here, we show the application of 3D geophysical imaging to assess the recharge potential and its variation across several basins used for managed aquifer recharge. We link in-situ measurements of saturated hydraulic conductivity with the electrical resistivity of the subsurface to establish petrophysical relationships and use those relationships to estimate the distribution of hydraulic conductivity throughout the five recharge basins. Our results show a considerable variability in the hydraulic properties, i.e., soil texture and saturated hydraulic conductivity, that have a direct impact on potential infiltration rates. We use the 3D hydraulic property distributions to model groundwater recharge and provide estimates for infiltration rates and volumes, and use this approach to assess the impact of management activities on groundwater recharge performance. Having such data not only enables us to predict infiltration rates, but also provides means for optimizing such water infrastructure.

Conducting an accurate hydrological water balance at the regional and country-wide scales is paramount to assessing available water resources and adequately allocating them. One of the main components of these balances is the anthropogenic recharge of groundwater either intentionally, through managed aquifer recharge (MAR), or unintentionally, where infiltration from dams and dykes can play a significant role. In Spain, proper management of water resources is critical due to the arid to semiarid conditions prevalent in most of the territory and the relevance of water resources for maintaining a robust agricultural sector. Previous work estimated country-wide recharge from MAR at 150 to 280 Mm3/year. Recently, water authorities pointed out that, according to hydrological water balances, the total unintentional recharge volume from water courses may exceed 500 Mm3/year. The present research aims to present a new inventory of transverse structures (also referred to as small dams and dykes) in Spain and use it to estimate country-wide unintentional recharge. The inventory, compiled by the Spanish Ministry for the Ecological Transition and the Demographic Challenge, has 27,680 structures and includes construction and impoundment characteristics, which allow for estimating the wet perimeter and the infiltration area. To this end, structural data from the inventory were crossed through map algebra in a GIS environment with thematic layers, such as lithology, permeability, the digital elevation model, the transverse structures’ wetted area, the average groundwater levels, and a clogging correction factor. Two analytical formulas to compute infiltration from small dams and dykes were tested. The resulting volume of unintentional recharge from transverse structures ranges between 812.5 and 2716.6 Mm3/year. The comparison against regional and national water balances suggests that the lowest value of the range (i.e., 812.5 Mm3/year) is probably the most realistic. Anthropogenic recharge from MAR and transverse structures is likely in the range of 1012.5–1514.8 Mm3/year. This rough figure can help close the hydrological balance at the national and river basin levels and contribute to calibrating regional models. Furthermore, they provide an order of magnitude for anthropogenic recharge at a national scale, which is difficult to obtain.

Water management in snowmelt hydrologic regimes, characterized by large annual fluctuations in stream flow driven by seasonal snow melt, faces the challenge of highly variable supply that often does not align with timing of demand. Climate change may exacerbate management challenges by significantly reducing snowpack or shifting snow melt earlier. Here, managed aquifer recharge (MAR) is evaluated as a potential strategy to reallocate excess early-season stream flow to time periods when less surface water is available. This strategy differs from traditional MAR, where the goal is to minimize loss to surface water. We assess how to site MAR operations such that groundwater recharge flows back to the surface water system in a lagged manor to benefit water management objectives, which we term “enhanced baseflow.” We use a regional groundwater model for the Treasure Valley aquifer located in southwestern Idaho, United States to demonstrate a generalizable approach using regional groundwater models as tools to identify favorable baseflow enhancement locations. Hypothetical MAR is simulated at 197 candidate locations, which are then evaluated for how effectively they meet potential management objectives. In addition to demonstrating the modeling and evaluation approach, we discuss lessons learned from applying a pre-existing regional groundwater model to MAR for enhanced baseflow and also describe important considerations, such as the physical and institutional availability of surface flows and specific management objectives, when assessing regional and site-specific suitability of MAR for enhanced baseflow as a potential management strategy.

The Mississippi Embayment aquifer is one of the largest alluvial groundwater aquifers in the United States. It is being excessively used, located along the lower Mississippi River covering approximately 202,019 km2 (78,000 square miles). Annual average groundwater depletion in the aquifer has been estimated at 5.18 billion cubic meters (Gm3) (4.2 million acre‐feet) in 1981–2000. However, since 2000, annual groundwater depletion has increased abruptly to 8 Gm3 (2001–2008). In recent years, multi‐state efforts have been initiated to improve the Mississippi Embayment aquifer sustainability. One management strategy of interest for preserving groundwater resources is managed aquifer recharge (MAR). In this study, we evaluate the impact of different MAR scenarios on land and water use decisions and the overall groundwater system using an economic model able to assess profitability of crop and land use decisions coupled to the Mississippi Embayment Regional Aquifer Study (MERAS) hydrogeologic model. We run the coupled model for 60 years by considering the hydrologic conditions from the MERAS model for the years 2002–2007 and repeating them 10 times. We find MAR is not economically attractive when the water cost is greater than $0.05/m3. Groundwater storage is unlikely to improve when relying solely on MAR as groundwater management strategy but rather should be implemented jointly with other groundwater conservation policies. [ABSTRACT FROM AUTHOR]

Jinan, China, is famous for its springs. However, societal and economic development over the past decades has detrimentally altered the natural water cycle in the spring area. Managed aquifer recharge (MAR) is an effective measure to ensure the normal gushing of springs. Balancing water resource utilisation, ecological effects, and water quality risks is not always easy to implement. This study focused on the potential effects of MAR projects that divert water from multiple local surface water sites, e.g., the Yellow River and South-to-North Water Diversion (SNWD) Project. A numerical simulation model for the entire spring area was built using MODFLOW and MT3DMS. The SNWD Project diverts water with relatively high total dissolved solids (TDS) to the Yufu River, which consequently recharges groundwater and poses a potential risk to the downstream karst water in the Jinan Spring area. Different simulation scenarios were set, and the results showed that the 90% recovery ratio scheme yields the highest TDS reduction efficiency as well as the largest karst water extraction volume. In addition, the water table remains stable as a whole. The benefits of the designed scheme are multifold, including improving water quality up to Standard III groundwater quality and meeting the water needs of the economy. The study provides a novel method of addressing the groundwater quality risks posed by artificial recharge. [ABSTRACT FROM AUTHOR]

The optimization of dam operations to transform them into multi-objective facilities constitutes a challenge for both hydrology, hydrogeology, and hydropower generation. However, the use of the optimal algorithm for such transformation is critically important. Additionally, the literature has highlighted that dams might negatively influence the recharge of groundwater. Within this study, we provide an overview of the available algorithms for the optimization of dam operations. Additionally, an overview focusing on hydropower generation in Greece illustrates the high potential of the Mediterranean region for hydropower generation and the application of MAR. The water quality of the reservoirs is also highlighted as a critical parameter. Within this study, we present indices for water quality monitoring in dam reservoirs, while the most prevailing index is the SRDD. This study constitutes a guide for researchers in choosing the optimal tools for the optimization of dam operations and the water quality monitoring of reservoirs. The present study suggests a meta-heuristic optimization methodology using the harmony search algorithm. The model uses a geometric model of the reservoir and calculates the level–supply curve. Furthermore, a multi-criteria optimization model was developed with two objective functions: the maximum power output from the hydroelectric power plant turbines and the optimal groundwater recharge. The model with appropriate parameter modifications can be applied to any small dam as it is a decision- and policy-making methodology, independent of local conditions. A further step is the application of these approaches dealing with field data and the numerical modeling of case studies. The interdisciplinary approach of this study links deferent aspect and scientific perceptions, providing a comprehensive guide to optimal water resource management and environmental sustainability. [ABSTRACT FROM AUTHOR]

Under possible risk of compound impacts of climate and anthropogenic changes, the Managed Aquifer Recharge (MAR) is envisaged to be an appropriate solution. Site suitability mapping is a crucial step in MAR project planning which requires various data, processing and GIS analysis. An automated web-based tool, named G-MCDA, is developed in this study for quick and efficient suitability mapping. G-MCDA integrates Google Earth Engine (GEE), Multi-criteria Decision Analysis (MCDA), GIS and web-based interface that allows automated data downloading, GIS data processing and suitability analysis using MCDA. G-MCDA has been tested in upper Ganga-Yamuna Doab region, India, for site suitability analysis. The application of G-MCDA shows that most of the area (82%) is under suitable category followed by very suitable (12%), and moderately suitable (5%). The suitable area is mostly flat agricultural lands with alluvium aquifer. A few patches of urban and sloping lands found to be moderately/low suitable for MAR. [ABSTRACT FROM AUTHOR]

BACKGROUND: Drinking-water salinity has been associated with high blood pressure (BP) among communities in south-west coastal Bangladesh. We evaluated whether access to water from managed aquifer recharge (MAR)-a hydrogeological intervention to lower groundwater salinity by infiltrating rainwater into the aquifers-can reduce community BP. METHODS: We conducted a stepped-wedge cluster-randomized trial with five monthly visits between December 2016 and April 2017 in 16 communities. At each visit following baseline, four communities were randomized to access MAR water. Systolic BP was the primary outcome, measured during each visit using Omron® HEM-907 devices. We also measured participants 24-hour urinary sodium and households drinking- and cooking-water salinity each visit. We used multilevel regression models to estimate the effects of MAR-water access on participants BP. The primary analysis was intention-to-treat. RESULTS: In total, 2911 person-visits were conducted in communities randomized to have MAR-water access and 2834 in communities without MAR-water access. Households without MAR-water access predominantly used low-salinity pond water and 42% (range: 26-50% across visits) of households exclusively consumed MAR water when access was provided. Communities randomized to MAR-water access had 10.34 [95% confidence interval (CI): 1.11, 19.58] mmol/day higher mean urinary sodium, 1.96 (95% CI: 0.66, 3.26; p = 0.004) mmHg higher mean systolic BP and 1.44 (95% CI: 0.40, 2.48; p = 0.007) mmHg higher mean diastolic BP than communities without MAR-water access. CONCLUSIONS: Our findings do not support the scale-up of MAR systems as a routine drinking-water source, since communities that shifted to MAR water from the lower-salinity pond-water source had higher urinary sodium and BP.