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Underground dams are a technology for artificially increasing existing groundwater resources. They modify the natural groundwater flow in aquifers and, typically, cause hydraulic heads to rise upstream and fall downstream of the dam. However, such modifications must be defined to forecast their environmental, economic and/or social impacts. A steady-state semianalytical solution is proposed for evaluating the two-dimensional distribution of hydraulic head caused by an underground dam fully penetrating a homogeneous and inclined aquifer. The dam is impermeable, of rectangular shape, and its length concerns a limited part of the aquifer width. The developed solution is based on the method of fundamental solutions. Analysis of the semianalytical solution included sensitivity tests and a satisfactory comparison with numerical modelling. Dimensionless graphs relating the dam geometry to maximum hydraulic-head variations upstream and downstream of the dam are given. The proposed solution was applied at two field sites, giving satisfactory results. A semianalytical solution is also developed for an artificial recharge area and/or a pumping well near the underground dam. Interestingly, in the case of highly permeable aquifers, the increase in hydraulic head created by the dam may be much higher than that created by managed aquifer recharge (MAR), despite high injected flux. These semianalytical solutions will be useful applications for assessing the long-term spatial distribution of hydraulic head induced by underground dams, or for testing the combination of dams with pumping wells or MAR technology. They are intended to guide the design of such structures, especially to quickly test various configurations. [ABSTRACT FROM AUTHOR]

Vadose zone wells (VZW), or drywells, allow for high infiltration rates combined with small area demand. Nevertheless, they are rarely used for managed aquifer recharge, since turbid water leads to gradual clogging and a reduction in infiltration capacity. Established redevelopment measures require backflushing, which is commonly considered impossible for VZWs, making them "non regenerable". In this study, the possibility of backflushing a VZW is discussed. Key to the underlying approach is isolating the lower (clogged) section of a well and saturating its surrounding with water by infiltration via the upper (unclogged) screen. Subsequently, underpressure sucks water from the surrounding soil into the isolated section. The approach was tested with and without a gravel pack, on laboratory scale, showing a successful reversal of flow direction in both cases. The degree of redevelopment was quantified by measuring the drainage time of the well, which increased from initially 45 s without gravel pack and 40 s with gravel pack to 9,500 and 11,000 s, respectively, after clogging. After backflushing, the well with gravel pack showed a median drainage time of 95 s, which remained stable over ten cycles of clogging and backflushing. In contrast, drainage time of the well without gravel pack increased continuously to >170 s, even after vibrator application. In conclusion, it can be stated that the backflush of a VZW with the presented approach is possible and has an effect on the well's infiltration capacity, though it seems more effective for wells with gravel pack. [ABSTRACT FROM AUTHOR]

The article presents the discussion on significance of groundwater (GW) globally and its management challenges, particularly focusing on India's situation. Topics include highlights the over-exploitation of groundwater resources in India, emphasizing the need for sustainable management practices to address water security issues; and global groundwater significance, challenges in groundwater management, and India's groundwater situation.

In deep excavations, pre-excavation dewatering (PED) usually causes notable diaphragm wall (D-wall) deformation and ground settlement. However, this problem has not attracted sufficient attention. In this paper, the mechanisms and control methods of settlement caused by PED in a deep excavation in Tianjin, China are analysed. A hydraulic connection between the soil inside and outside the excavation area due to aquifer leakage was observed during PED. Therefore, although the first level of struts had been installed before PED, the deformation of the D-wall and ground settlement reached 6·9 mm and 12·5 mm, approximately 29·0% and 73·5% of the maximum allowable values, respectively. The monitoring results demonstrated that leaky aquifers could reduce the deformation of the D-wall but increased the magnitude and extent of ground settlement. Based on the numerical simulations of D-wall deformation and groundwater change, in this case, the ground settlement within the area extending two times the depth of unloading (two times the depth of dewatering, 2Hd) from the excavation was found to be caused by both the deformation of the D-wall and the drawdown of the groundwater, whereas the noticeable settlement in the area beyond 2Hd was caused by only the drawdown of the groundwater. When hydraulic connections exist between the soil inside and outside the excavation area, artificial recharge should be used to control the noticeable settlement induced by groundwater drawdown. [ABSTRACT FROM AUTHOR]

Quantifying water-saving potential (WSP) is crucial for sustainable water resource management in canal command areas and river basins. Previous studies have partially or fully ignored the importance of groundwater in WSP assessments, particularly in irrigated areas. This study is aimed at quantifying WSP in the Lower Chenab Canal (LCC) command area of the Indus River Basin, Pakistan, under various scenarios of future climate change and groundwater recharge. These quantifications are conducted using an empirical model based on the Budyko theory. The model was forced using observed, remote sensing, and CMIP6 future climate data for two Shared Socioeconomic Pathways (SSP245 and SSP585) and their ensembles (cold-dry, cold-wet, warm-dry, and warm-wet) for possible futures. The results showed that the average WSP in the LCC command area was 466 ± 48 mm/year during the historical period (2001–2020). The WSP is projected to decrease by – 68 ± 3% under the warm-dry ensemble scenario (SSP245 and SSP585) and – 48 ± 13% under the ensembled cold-wet scenario by 2100. The results also demonstrated that WSP could be increased by up to 70 ± 9% by artificially recharging 20% of the abstracted groundwater per year in the LCC command area by the late twenty-first century. Our findings highlight the importance of adopting artificial groundwater recharge to enhance the WSP and sustainably manage water resources in the LCC command area. Policymakers should consider these findings when deciding on water resource management in the Indus River Basin. [ABSTRACT FROM AUTHOR]

The flows of surface water and groundwater from the Andes to the Atacama Desert are a vital source of freshwater, supporting ecosystems and human activities, but few substantive studies have addressed the hydrological and hydrogeological functioning of these systems. A dispute between Chile and Bolivia concerning the transboundary Silala River, recently heard before the International Court of Justice, The Hague, provided a unique opportunity for new scientific studies, reviewed in this Special Issue. First, findings from field studies that address the geological and geomorphological evolution of the Silala River basin and its current status, the key hydrological processes (including infiltration, actual evaporation from wetlands and alluvial plains, and surface water‐groundwater interactions), and the hydrogeological characterization of the major aquifers are reviewed. The dispute arose because Bolivia disagreed that the Silala was a transboundary river, subject to international law. As the Court proceedings evolved, this was accepted by Bolivia, but effects on surface flows of historical channelization in the Bolivian headwater wetlands remained a point of legal and technical disagreement. Bolivia asserted large increases in surface flow, based on modeling by their consultants, DHI. Chile held that these effects are small. In the second part of this paper, we summarize the modeling evidence. Chile's use of DHI's models, and its own hydrological and groundwater modeling of the basin, fully support Chile's position. We conclude with discussion of the Court's judgment, the challenges of physically‐based modeling of small changes in complex systems, and associated implications for judicial practice. This article is categorized under:Human Water > Water GovernanceScience of Water > Hydrological ProcessesScience of Water > Water and Environmental Change [ABSTRACT FROM AUTHOR]

The chemistry of the groundwater of north coastal part of Odisha is primarily controlled by weathering of minerals present in basement rocks superimposed by anthropogenic activities and sea water intrusion. The water is hard and alkaline in nature, but most of the constituent ions excluding F- are within permissible limits for human consumption. Four factors satisfying over 86% of the total variance and three clusters corresponding to geogenic, alkaline and anthropogenic processes have been identified. Ca2+, Mg2+, Na+, K+, F−, CO32− and HCO3− are geogenic, contributed by the basement rocks and soils. Cl−, SO4− and NO3− are anthropogenic, derived from haphazard household waste disposal, overflows of septic tanks, return flow from irrigation, animal wastes, manures, soil conditioners and chemical fertilizers. K+ and F− belong to both the categories while Na− and Cl− are contributed by saline intrusion to some extent. The pH, total alkalinity and F− represent alkaline component, while HCO3− is derived from weathering of minerals and influence of atmospheric CO2. Change of groundwater types from Ca-HCO3 (fresh water) → Ca-Mg-Cl → Na-Cl (saline water) as well as increase of total dissolved solids in seaward direction indicates the effect of seawater intrusion in the study area. Sympathetic relationship of F" with total alkalinity, pH and Na+ as well as negative correlation with Ca2+ suggest the prevalence of alkaline environment that favors dissolution of fluoride minerals of the basement rocks. It is suggested to minimize the anthropogenic activities like haphazard waste disposal and excessive use of agrochemicals, adopt artificial recharge measures, take up regular groundwater quality check and aware the public for proper management of groundwater resource in the study area. [ABSTRACT FROM AUTHOR]

India is at the brink of facing severe water scarcity situation. To overcome the challenge, the country plans to implement a mega managed aquifer recharge (MAR) scheme in pan-India scale with huge monetary investment, but for the scheme to succeed, it is essential that the MAR sites are favourable for recharge. The real challenge will be when the 10.6 million rooftop water harvesting structures under the scheme will be constructed in about 8000 towns and 500 urban agglomerates of India. Site-specific study will be essential for these structures to deliver their optimum performance. At present, many of these structures are constructed without adequate hydrogeological and subsurface geophysical investigations. As a result, demarcation of the exact depth of release of harvested rainwater in the aquifers becomes difficult. In an attempt to exemplify how these investigations could be carried out to effect favourable groundwater recharge, a case study has been taken up at the Gun Carriage Factory, Jabalpur, Madhya Pradesh in central India. Unlike similar geophysical studies carried out elsewhere with vertical electrical soundings, this technique was employed to decipher fracture depths, which were determined at a depth of about 15–35 m and confirmed subsequently by an on-the-spot recharge experiment. Fracture zones are porous and permeable horizons where harvested rainwater could be released at depth. This work recommends similar investigations to be carried out in specific areas where any kind of MAR scheme is envisaged so that the investments made deliver their optimum results. [ABSTRACT FROM AUTHOR]

Groundwater resources are crucial in arid and semiarid regions with limited rainfall and surface-water scarcity. However, these areas face challenges such as high evaporation and groundwater contamination, leading to dangerously low groundwater levels. This research identifies suitable locations for artificial groundwater recharge to address these challenges, improve long-term resource performance, and promote water conservation and storage. Artificial recharge sites were identified based on various criteria, in conjunction with geographic information system (GIS) methods, including slope, soil type, geology, geomorphology, land cover, groundwater depth, hydraulic conductivity, electrical conductivity, and drainage density. Each criterion was evaluated using the analytical hierarchy process (AHP), and experts from different disciplines contributed through pairwise comparisons. The study focuses on the Tamellalt region (Morocco) as a representative arid area. The AHP findings reveal that aquifer transmissivity is the most significant factor, accounting for 16.08% of the total influence, while the recharge component represents only 8.22%. Combining thematic maps generated a potential final map, indicating that 54% of the land is suitable for artificial groundwater recharge. These areas are further categorized as good, moderate, and poor, covering respective land areas of 183,600, 125,800, and 30,600 ha. These locations exhibit high infiltration potential and good water quality, making them favorable for artificial recharge, particularly in regions with significant pluvial water accumulation. Overall, this research provides insights into addressing groundwater depletion in arid regions. Identifying suitable sites for artificial recharge offers a potential solution to enhance long-term water resource management, promote conservation, and mitigate water scarcity challenges. [ABSTRACT FROM AUTHOR]

The Yongding River (Beijing, China) was dry most times of the year, and groundwater storage was severely depleted. To address this issue, a river rehabilitation project was initiated. A downstream environmental flow release (EFR) project from upstream reservoirs has been implemented since 2019. This study evaluated the impact of EFR by constructing transient groundwater-flow and numerical tracer transport models to simulate the hydrogeological responses to the water release events in 2019–2020. The study identified two factors that significantly influence the river leakage rate, which are operational factors (i.e., water release rate and duration) and physical factors (i.e., hydraulic properties of the riverbed, regional hydraulic gradients, and groundwater depth) that determine the maximum water availability for groundwater recharge and maximum infiltration capacity, respectively. Predictive modelling was performed to assess the long-term effects of the proposed EFR scheme from 2021 to 2050, which showed that groundwater levels along the river will increase by 10–20 m by 2050. Groundwater storage is expected to be largely recovered and groundwater/surface-water connectivity in the middle reach of the river will be restored. This restoration will not only maintain the environmental flow for the benefit of ecosystems but also enhance groundwater recharge, promoting sustainable groundwater development in the region. Overall, this study provides valuable insights into the effectiveness of the proposed EFR scheme in achieving sustainable groundwater development in the region. [ABSTRACT FROM AUTHOR]

In order to restore degraded wetlands, restoration projects were implemented in the Yellow River Delta wetland reserve from 2010. Water was diverted from the Yellow River and was used to saturate artificial wetlands. This study used in-situ data and model simulations to investigate the effects of water diversion on groundwater systems in the artificial wetlands in 2010, 2011, and 2013. The objectives were to: (1) develop a model for simulating groundwater flow within the study area using Visual MODFLOW, (2) apply the model to simulate and compare the water-table and water-balance responses to water diversion between years, and (3) compare several landscape scenarios that combine artificial shallow ponds and canals and investigate potential water efficiency improvements in the wetland reserve. Results indicate that precipitation infiltration, evapotranspiration, and wetland leakage were the most dominant water budget components. Water diversion increased groundwater storage and shifted the water tables. Between 2010 and 2013, as the water diversion volume in the restoration area near the Diaokou Channel increased, wetland leakage increased, and the spatial effect (meaning impact range on groundwater) of diversion increased from 800 to 1,000 m. Based on the scenario analysis, wetland canals have lower evapotranspiration losses, thus diversion canals that retain water for a longer duration improve the efficiency of water use. Artificial shallow ponds and canals may enhance surface-water/groundwater interactions and restore plant biodiversity. This study can provide a design reference for the construction of artificial wetlands in semiarid areas. [ABSTRACT FROM AUTHOR]

The article focuses on the impact of climate change on agriculture, particularly its influence on water availability, insect and disease patterns, and adaptation strategies in the agricultural sector. Topics include the challenges posed by climate-induced changes in water quantity and quality, the stimulation of pests and diseases by higher temperatures, and the diverse adaptation measures employed by both private and public sectors in agriculture.

Water scarcity is well pronounced in arid and semiarid regions where potential evapotranspiration exceeds precipitation. Saudi Arabia is one of the most water-scarce regions where there are 2 billion m³ of annual renewable freshwater resources, besides 24 billion m³ of freshwater withdrawal, especially from the aquifers with fossil water. In Saudi Arabia, floods often occur and the harvest of flood water for groundwater recharge became an issue of discussion; however, this requires determining groundwater recharge potential (GWRP) zones where water naturally percolates and feeds the depleted aquifers. This study aims to produce a detailed (digital) map for GWRP zones for the Riyadh Region by using a multicriteria approach where datasets were derived from satellite images (Landsat 7 ETM+, Spot-5, and Aster) associated with thematic maps and field surveys. The geo-information system (GIS) was also used to manipulate and integrate the geospatial data layers which represent the controlling factors on GWRP. Results show five classes of GWRP zones, where about 36,448 km² (89.2% of the Riyadh Region) belong to high and very high GWRP. The resulting map will be key information for decision-makers to select suitable localities for groundwater artificial recharge techniques as an adaptive measure for the changing climate. [ABSTRACT FROM AUTHOR]

India is the world's second-largest producer of fish, where the state of West Bengal is leading in fish production. The Sundarbans, located in the southern part of India's West Bengal state, is a UNESCO-designated world heritage site. The Indian Sundarbans is a tide-dominated region in the southern part of deltaic West Bengal, and is home to 4.43 million people. Even though it is traversed by numerous creeks and rivulets and receives a significant amount of precipitation during the monsoon season, freshwater is a scarce resource in the Sundarbans. During the dry season, there is a lack of fresh water above and below the ground, increasing siltation results in shallower channels, high salinity of the water and soil, and congestion in drainage making it difficult for people to make a living. During the dry season, most blocks experience water scarcity as a result of the ever-increasing population's demand for water. According to this study, Sundarbans' current annual domestic and drinking water demands are 105.1 mcm and 8.08 mcm, respectively. By combining the area under various crops and their lifecycle water requirements, the water demand for agriculture has been calculated to be 2782.83 mcm. The rainfall-runoff modelling aims to get a general idea of how much fresh water is available each year through surface runoff. It has also been estimated how much water is available from different sources in each block. It is estimated that deep and shallow bore wells contribute approximately 400 mcm, whereas surface water sources like tanks and canals contribute approximately 50 mcm. The communities that live in the Sundarbans eco-region benefit greatly from aquaculture's contribution to their socio-economic development. For the sustainable development of aquaculture in the Sundarbans Delta, strong technical, financial and extension services from government organisations and research institutions are urgently required to meet these obstacles. Additionally, this study emphasises that roof-top rainwater harvesting in this region has the potential to supply 45 mcm more water, which could be used to partially satisfy the region's domestic water demand. Future major policy options for meeting the Sundarbans ecoregion's water demand include large-scale rainwater harvesting, rejuvenation and reconnection of disconnected river channels, artificial recharge of shallow aquifers to lower their salinity, and de-salination of shallow groundwater. [ABSTRACT FROM AUTHOR]

Hypsometric analysis is a valuable tool for determining the tectonic evolution of a river basin and the erosion susceptibility. It is also important for integrated watershed management, which include selecting suitable locations for groundwater recharge structures and for conservation of soil and water. This type of study can analyze the relationship between horizontal cross sectional area and the altitude of the watershed. It evaluates the hypsometric curve and hypsometric integral, as generated for the WRC-1 watershed, Chargarh river basin through remote sensing and GIS technique. In the present case, hypsometric analysis was carried out using Survey of India topographic maps, Arc map-10.2 software and SRTM-DEM. The hypsometric integral is calculated using mean elevation minus minimum elevation, divided by relief. The hypsometric curve, with a value of 0.69 for the hypsometric integral clearly indicates an inequilibrium stage (youthful stage) of geomorphic development, which is highly susceptible to erosion. These interpretations can further utilize appropriate measures of soil and water conservation for long-term development within the WRC-1 watershed. [ABSTRACT FROM AUTHOR]

Groundwater is a precious natural resource that is vital to various aspects of life. Punjab is experiencing groundwater stress due to urbanization and population growth, leading to overuse and reduced aquifer recharge. Sustainable groundwater supplies can only be created through better management and artificial recharge techniques. This study uses multi-influencing factor, literature-based, and combined techniques to identify and characterize groundwater-managed aquifer recharge potential sites (GWMARPSs) in Punjab. There are limitations to the previous work in this field, and these factors have not been used to estimate GWRPSs in the study area. The study uses GIS and RS techniques to overlay twelve geo-informative layers, with rainfall being the most significant factor. High-quality data and observations from the field are incorporated into the model. The study classifies the GWMARPSs into five categories, with Punjab having 0.34%, 13.29%, 60.68%, 25.26%, and 0.43% of the least, poorly, moderately, well-, and highly suitable sites. Punjab's southern regions are least suitable for recharge, while some areas in eastern and northern Punjab are well-suited for recharge. Alluvial plains, valleys, low-lying areas, and areas with volcanic landforms are classified as least to poorly suitable zones. Model predictions are validated using piezometric level data and ROC and exhibit good performance (AUC, 0.74). This study could serve as a baseline for future groundwater research. [ABSTRACT FROM AUTHOR]

Globally, climate change is triggering shifts in water availability, especially across arid and desert landscapes similar to that in Yemen, where precipitation patterns are increasingly erratic. Here, we use water budget calculations, drought metrics, and trend analyses to examine climatic water deficits, with the aim of unraveling irrigation demands and overall water stress across Yemen. The results indicate that 94% of the influx is lost back to the atmosphere via evapotranspiration, 6% is converted to runoff, and only a negligible amount, generally less than 1%, is retained as storage. The results also show an unrelenting, statistically significant water deficit increase of 0.17 mm yr−1 on the Sen's slope, at the critical Z-value of 0.005 across the country, for the past 63 years. Our findings challenge the conventional understanding of water deficits across Yemen and suggest that the country's water resources situation is direr than was earlier documented. Further results show that while the water shortage mosaic across the country experiences interannual variations, their occurrence is significantly intensifying. As such, an immediate and radical modernization of integrated water management systems, including concerted investments in irrigation and artificial recharge wells, especially across the Arabian Sea Coast, the Red Sea Coast, and the Highlands, is strongly recommended. [ABSTRACT FROM AUTHOR]

For production of clean drinking water, the processes governing bacterial remobilization in the unsaturated zone at transient water flow are critical. Although managed aquifer recharge is an effective way to dispose of pathogens, there are concerns about recontamination after heavy precipitation. To better understand how bacteria that were initially retained in porous media can be released to groundwater due to transient water content, transport experiments and modeling for Escherichia coli and Enterococcus moraviensis were conducted at the soil column scale. After inoculating dune sand columns with a bacteria suspension for 4 h, three rainfall events were performed at 24-h intervals. The effluent from sand columns was collected to analyze bacteria breakthrough curves (BTCs). After the rainfall experiments, the bacteria distribution in the sand column was determined. The collected BTCs and profile retentions were modeled with HYDRUS-1D, using different model concepts, including one-site kinetic attachment/detachment (M1), Langmuirian (M2), Langmuirian and blocking (M3), and two-site attachment/detachment (M4). After inoculation, almost 99% of the bacteria remained in the soil. The M1 and M2 bacteria models had a high agreement between observed and modeled concentrations, and attachment and detachment were two significant mechanisms for regulating bacteria movement in a porous medium with fluctuations in water flow. At the end of the experiment, the majority of bacteria were still found within the depth range of 5 cm to 15 cm. Our experiments show that E. coli is more mobile in sandy soils than E. moraviensis. The results of this study also suggest that the unsaturated zone is an important barrier between microbial contamination at the soil surface and groundwater. Follow-up studies are needed to completely understand the variables that regulate bacteria remobilization in the unsaturated zone of dune sands. IMPORTANCE At managed artificial recharge sites in the Netherlands, recontamination of infiltrated water with fecal indicator bacteria has been observed. The results of this study suggest that the unsaturated zone is an important barrier between microbial contamination at the soil surface and groundwater. Bacteria that accumulate in the unsaturated zone, on the other hand, can multiply to such an extent that they can be released into the saturated zone when saturation increases due to major rain events or a rise in groundwater level. [ABSTRACT FROM AUTHOR]

Groundwater management requires a systematic approach since it is crucial to the long-term viability of livelihoods and regional economies all over the world. There is insufficient groundwater management and difficulties in storage plans as a result of increased population, fast urbanisation, and climate change, as well as unpredictability in rainfall frequency and intensity. Groundwater exploration using remote sensing (RS) data and geographic information system (GIS) has become a breakthrough in groundwater research, assisting in the assessment, monitoring, and conservation of groundwater resources. The study region is the Mand catchment of the Mahanadi basin, covering 5332.07 km2 and is located between 21°42′15.525″N and 23°4′19.746″N latitude and 82°50′54.503″E and 83°36′1.295″E longitude in Chhattisgarh, India. The research comprises the generation of thematic maps, delineation of groundwater potential zones and the recommendation of structures for efficiently and successfully recharging groundwater utilising RS and GIS. Groundwater Potential Zones (GPZs) were identified with nine thematic layers using RS, GIS, and the Multi-Criteria Decision Analysis (MCDA) method. Satty's Analytic Hierarchy Process (AHP) was used to rank the nine parameters that were chosen. The generated GPZs map indicated regions with very low, low to medium, medium to high, and very high groundwater potential encompassing 962.44 km2, 2019.92 km2, 969.19 km2, and 1380.42 km2 of the study region, respectively. The GPZs map was found to be very accurate when compared with the groundwater fluctuation map, and it is used to manage groundwater resources in the Mand catchment. The runoff of the study area can be accommodated by the computing subsurface storage capacity, which will raise groundwater levels in the low and low to medium GPZs. According to the study results, various groundwater recharge structures such as farm ponds, check dams and percolation tanks were suggested in appropriate locations of the Mand catchment to boost groundwater conditions and meet the shortage of water resources in agriculture and domestic use. This study demonstrates that the integration of GIS can provide an efficient and effective platform for convergent analysis of various data sets for groundwater management and planning. [ABSTRACT FROM AUTHOR]

An accurate estimation of river channel conveyance capacity and the water exchange at the river–floodplain interfaces is pivotal for flood modelling. However, in large-scale models limited grid resolution often means that small-scale river channel features cannot be well-represented in traditional 1D and 2D schemes. As a result instability over river and floodplain boundaries can occur, and flow connectivity, which has a strong control on the floodplain hydraulics, is not well-approximated. A subgrid channel (SGC) model based on the local inertial form of the shallow water equations, which allows utilization of approximated subgrid-scale bathymetric information while performing very efficient computations, has been proposed as a solution, and it has been widely applied to calculate the wetting and drying dynamics in river–floodplain systems at regional scales. Unfortunately, SGC approaches to date have not included the latest developments in numerical solutions of the local inertial equations, and the original solution scheme was reported to suffer from numerical instability in low-friction regions such as urban areas. In this paper, for the first time, we implement a newly developed diffusion and explicit adaptive weighting factor in the SGC model. Adaptive artificial diffusion is explicitly included in the form of an upwind solution scheme based on the local flow status to improve the numerical flux estimation. A structured sequence of numerical experiments is performed, and the results confirm that the new SGC model improved the model performance in terms of water level and inundation extent, especially in urban areas where the Manning parameter is less than 0.03 m -1/3 s. By not compromising computational efficiency, this improved SGC model is a compelling alternative for river–floodplain modelling, particularly in large-scale applications. [ABSTRACT FROM AUTHOR]

Artificial recharge is an effective remediation measure for controlling groundwater level and subsidence in many coastal cities in China. Hydraulic parameters estimated by pumping tests are often used in the design of both pumping and recharge systems. However, the hydraulic parameters in the recharge process have been found to differ from those in the pumping process and should be studied in greater detail. Eight single-well pumping and recharge tests were conducted within a confined aquifer in a soft soil area in the city of Tianjin, and the differences in wellbore storage influences and well losses between the recharge and pumping processes were examined. Furthermore, based on the Hantush and Jacob model, an algorithm combining the Levenberg–Marquardt algorithm (LMA) and genetic algorithm (GA) was employed for estimation of the hydraulic parameters. The results illustrated that the combined algorithm eliminating wellbore storage influences could provide hydraulic parameters from which the groundwater level variation could be accurately simulated. The hydraulic conductivity and specific storage values obtained in the pumping tests were higher than those obtained in the recharge tests. In addition to slight plugging of the recharge well, the specific storage differences could be explained by the compression and rebound deformation characteristics of sand in the confined aquifer. The specific storage estimated by pumping tests should be adjusted when applied in groundwater recharge calculation. [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 recharge. [ABSTRACT FROM AUTHOR]

In order to solve the problem that the cold/heat released from the underground pipe of coal mine into the soil layer is difficult to dissipate in a short time, the technology of enhancing the underground flow field of coal mine in geothermal energy development to improve the energy efficiency of the heat pump system is proposed. In this paper, based on the ground source heat pump project located in a coal mine, the energy efficiency enhancement technology of the artificial flow field ground source heat pump system is studied and tested. The test results show that when starting work at about 8:00, due to the increase of heating load, the accumulation of cooling capacity around the buried pipe increases gradually, and the return water temperature at the ground source side decreases gradually. At 14:05, the water was pumped for the operation of the artificial groundwater flow field. It can be seen that the temperature of the return water at the ground source side began to rise gradually, indicating that the accumulation of cold water around the buried pipe was relieved to a certain extent. In conclusion, the artificial groundwater flow field can alleviate the accumulation of cold water around the buried pipe heat exchanger to a certain extent, improve the return water temperature of the buried pipe heat exchanger, and improve the energy efficiency of the ground source heat pump system. [ABSTRACT FROM AUTHOR]

The Daqinghe River basin is the most prominent area of groundwater overdraft in the Haihe River basin. In order to solve the problem of groundwater overdraft, this study carried out the suitability evaluation of integrated groundwater recharge in mountainous and plain areas in the basin. Select the buried depth of groundwater level, permeability coefficient, distance from the main canal of the middle line of the South-to-North Water Transfer, distance from the reservoir, precipitation infiltration coefficient, effective water storage space, slope, and surface elevation to build the GIS-AHP decision model to obtain the zoning map of the suitability of the study area, and use numerical simulation to evaluate the effect of the replenishment. The study shows that the suitable areas for recharge are mainly distributed in the piedmont reaches of Juma River, Qinglong River, Tanghe River and Cihe River, accounting for 4. 5% of the total assessed area; at the same time, according to the assessment results of the suitability of recharge, the refined water replenishment scheme for river sections can greatly slow down the decline rate of groundwater storage variables, and the recharge is the best. Therefore, the suitable assessment of groundwater recharge in the basin based on the combination of GIS and numerical simulation is helpful to greatly improve the utilization efficiency of water resources in the region and provide the optimal over- extraction control scheme. [ABSTRACT FROM AUTHOR]

Artificial recharge of groundwater increases the water level in an aquifer, which can be used for water security in a drought-prone region. This study was conducted to identify the interval of injection wells in a small basin upstream of a watershed. For the pilot test, 11 injection wells were installed, in which individual and simultaneous injections were performed. The rates of the individual and simultaneous injections ranged from 0.49–38.13 and 0.04–11.48 m3/d, respectively. Simultaneous injection resulted in a reduced injection rate of approximately 4.4–95.4% compared to that of individual injection owing to the interference effect of the injection wells. Moreover, the hydraulic conductivity of each well and the radius of influence were used to analyze the interference effect during injection using the Thiem-Dupuit equation. The interference effect between injection wells was evaluated by increasing the space from 2 to 15 m at four recharge lines (total length: 340 m) within the study area, and the expected injection rate was calculated as the rates of 220.85–58.95 m3/d. On the other hand, construction cost for installing injection wells became higher at 2 m interval than at 15 m. Therefore, there was no significant increase in construction cost per 1-m3 injection volume as well as decrease in total injection rate if the well interval was > 5 m and the optimum interval of injection well was suggested to be at least 5 m. Drought-prone areas are generally excluded from water-welfare benefits and are economically fragile; consequently, when developing an artificial recharge facility, injection wells should be designed considering the security of suitable amount of water with economic feasibility. [ABSTRACT FROM AUTHOR]

Managed aquifer recharge (MAR) is an emerging approach to enhancing water storage capacity, improving water supply security and countering groundwater overexploitation. However, physical clogging, i.e. accumulation of suspended organic and inorganic solids within a sediment matrix, can lead to a significant reduction of infiltration rates and present difficulties in the functioning of MAR infrastructure. Clogging and subsequent reduction in infiltration capacity are often quantified based on monitoring data or field investigations, rather than on forecasts. Existing predictive models require specific parameterisation, making an application to heterogeneous sites, or under changing conditions, difficult. Hence, a generalised understanding of how intrusive fine particles distribute over depth during water recharge cycles for typical MAR infiltration basin sediments is needed to predict clogging susceptibility and clogging patterns already in the planning phase and before operation of MAR schemes. The study will contribute to operational reliability, deduce optimised management practices, and, ideally, reduce maintenance efforts. To achieve this goal, data from different soil-column clogging experiments are reviewed and complemented with experiments to establish a generally valid relationship for the vertical distribution of intrusive fines under consideration of the primary porous media's and intruding particles' characteristics. Obtained results allow for quantification of the amount of particles retained at the surface of the porous media, i.e. formation of a filter cake, a description of the distribution of fines over depth, and total clogging depth. Finally, the findings are applied to a real MAR case study site to showcase the quantification of clogging effects on recharge rates. [ABSTRACT FROM AUTHOR]

Excessive extraction, uncontrolled withdrawal of groundwater, and unregulated practices have caused severe depletion of groundwater resources in the Erbil basin, Iraq. This situation has had a number of negative consequences on human settlement, agricultural activities, clean water supply, and the environment. Runoff harvesting and artificial groundwater recharge play a significant role in the sustainable management of water resources, particularly in arid and semi-arid regions. This study aims to: (1) delineate groundwater recharge zones using multiple thematic layers that control the groundwater recharge process, and (2) identify prospective sites and structures to perform artificial groundwater recharge. In order to generate a potential map for groundwater recharge zones, seven thematic layers are considered in this study, namely, topographic position index, geomorphology, lithology, land cover, slope, drainage-length density, and lineament-length density. After that, the analytic hierarchy process was applied to weight, rank, and reclassify these seven thematic layers. All maps are then integrated within the ArcGIS environment for delineating groundwater recharge zones. Accordingly, the resulting map categorizes the study area into five zones: extremely high, high, moderate, low, and extremely low potential for groundwater recharge. As expected, areas along the Greater Zab river show the highest possibility for groundwater recharge. Likewise, rugged eastern hills demonstrate an encouraging capacity for artificial aquifer recharge, whereas the least effective area is represented by built-up land. Based on the generated map, two dams are proposed as promising artificial recharge structures for harvesting runoff water east of Erbil city. Lastly, the resulting map of the potential groundwater recharge zones is verified using static water level data, where the coefficient of determination (R²) achieved a satisfactory result (0.73). These findings provide crucial evidence for implementing a sustainable management plan for surface and groundwater resources. The applied method is eventually valid for regions where appropriate and adequate field data availability is a serious issue. [ABSTRACT FROM AUTHOR]

Morphometry of a basin's reaction to a particular hydrology, in particular in river basins where agriculture is the dominant industry, offers knowledge for watershed management. In order to gain an understanding of the hydrological situation for the Warana River basin as a case study location in Maharashtra, an attempt was made to comprehend the morphometric features. Geoprocessing methods in QGIS 3.16 were used to calculate the morphometric parameters. Seventh-order Warana River basin has a dendritic drainage pattern with high stream frequency (2.99/km), infiltration number (7.22), and drainage density (2.41 km/km2), indicating high runoff potential; and a low Constant of channel maintenance (0.41) and lineament density (0.20 km/km2), indicating moderate recharge potential. The basin has a moderate flood and recharge property, according to the interrelationship among the morphometric factors. The Warana River basin has regular floods, according to the flood frequency analysis done for the Shigaon River gauging station. Decadal time scales for water table variations revealed moderate to high recharge characteristics. The study's conclusions can be used to categorize river basins for future developments and for the management of water resources, as well as to choose the best sites for water-conservation infrastructure, such as check dams, percolation tanks, and artificial groundwater recharge. [ABSTRACT FROM AUTHOR]

Islamabad is essentially the only well-planned city in Pakistan, but groundwater depletion has become a serious issue there because of the rapid increase in population, poor water management, and deforestation. The current water demand of the city is about 220 million gallons per day, with the Capital Development Authority (CDA) providing up to 70 million gallons per day. The need for water is mostly fulfilled through groundwater sources, such as water bores and commercial tube wells. Hence, identifying recharge sites for natural aquifers is a significant component of groundwater required to overcome the water crisis. Therefore, this study aims to identify potential sites for natural aquifer recharge by using analytical hierarchy process (AHP), weighted linear combination (WLC), and fuzzy logic methods. To achieve the stated objective, seven local influencing factors including soil, slope, water table, population density, land use land cover (LULC), drainage density, and elevation have been utilized in this study. AHP was utilized for the evaluation of the relative importance of the above-mentioned factors, while fuzzy logic was applied for the standardization of these factors. Finally, the AHP-WLC and fuzzy logic approaches were used to merge factor maps in order to identify suitable sites for natural aquifer recharge in Islamabad City. Two different suitability maps were constructed from both techniques, and on each of the resulting maps, the subregions were categorized into five classes: not suitable, less suitable, moderate, suitable, and most suitable. Based on the AHP-WLC results, 5% of the whole study area is deemed most suitable for natural aquifer recharge (NAR), whereas from the fuzzy logic results, 10% of the study area is marked as most suitable. In contrast, 37% and 32% of the whole study area were identified as suitable by the AHP-WLC and fuzzy logic methods, respectively. While both techniques can obtain satisfactory outcomes, the suitability map from fuzzy logic has produced more precise results. Hence, we propose to CDA-Islamabad here different sites for recharge wells based on the results of fuzzy logic. As recommended by this study, to date CDA has constructed twelve recharge wells. [ABSTRACT FROM AUTHOR]

Groundwater levels are gradually declining in basins around the world due to anthropogenic and natural factors. Climate is not the only factor contributing to change in groundwater levels, population growth and economic progress are leading to increased water demand. Areas used for agricultural irrigation are expanding, necessitating the use of artificial groundwater recharge as a method to sustain pumping and enhance storage. The present study delineates potential locations of significant groundwater resources that already exist using a geostatistical approach as a method to identify potential groundwater recharge zones. The Multi-Influencing Factors (MIF) technique was applied to determine the relationship between different landscape and climatic factors that influence groundwater recharge. Factors include topography, climate, hydrogeology, population, economic change, and geology. Integration of these factors enabled the identification of potential locations of groundwater suitable for artificial recharge efforts based on weights derived through the MIF technique. We applied these weights to derive a groundwater recharge index (GRI) map. The map was delineated into three groundwater recharge zones classified by their potential areal coverage as a metric for recharge suitability, namely low, medium and high suitability, occupying areas of 8625 km2 (30.06%), 9082 km2 (31.65%), and 10,989 km2 (38.29%), respectively. Our findings have important implications for designing sustainable groundwater development and land-use plans for the coming century. [ABSTRACT FROM AUTHOR]

Groundwater recharge potential is an important spatial analysis to refer where the groundwater recharge is likely to happen. The present study discusses approaches for determining groundwater recharge potential zones in the Guder watershed, Ethiopia, using geospatial and fuzzy logic techniques on derived thematic layers based on significant influence of groundwater occurrence. A variety of thematic layers were created using satellite images and other ancillary data, including drainage density, slope, rainfall, geology, land use/land cover, lineament density, soil, and geomorphology. Researchers, expert opinion, and previous studies were used to estimate the membership value for each governing factors. According to the findings of the study, approximately 5.25% of the area has very high groundwater recharge potential, and 9.34% of the area has high groundwater recharge potential, while the areas with very low, low, and moderate groundwater recharge potential are approximately 20.04%, 34.21%, and 31.15%, respectively. The study's findings were confirmed by looking at the cross-tabulation area between the contributing features and the final map, which demonstrated strong associations. The findings of the study will help decision-makers and policymakers plan to implement appropriate groundwater recharge procedures. Fuzzy logic approaches have been found to be a basic tool for estimating groundwater recharge locations when used with GIS. [ABSTRACT FROM AUTHOR]

Groundwater recharge potential is an important spatial analysis to refer where the groundwater recharge is likely to happen. The present study discusses approaches for determining groundwater recharge potential zones in the Guder watershed, Ethiopia, using geospatial and fuzzy logic techniques on derived thematic layers based on significant influence of groundwater occurrence. A variety of thematic layers were created using satellite images and other ancillary data, including drainage density, slope, rainfall, geology, land use/land cover, lineament density, soil, and geomorphology. Researchers, expert opinion, and previous studies were used to estimate the membership value for each governing factors. According to the findings of the study, approximately 5.25% of the area has very high groundwater recharge potential, and 9.34% of the area has high groundwater recharge potential, while the areas with very low, low, and moderate groundwater recharge potential are approximately 20.04%, 34.21%, and 31.15%, respectively. The study's findings were confirmed by looking at the cross-tabulation area between the contributing features and the final map, which demonstrated strong associations. The findings of the study will help decision-makers and policymakers plan to implement appropriate groundwater recharge procedures. Fuzzy logic approaches have been found to be a basic tool for estimating groundwater recharge locations when used with GIS. [ABSTRACT FROM AUTHOR]

In this article, we propose and study a second order, artificial compressibility ensemble method with different subdomain time steps for the Stokes–Darcy equations, which are the core model for simulating the coupled surface‐groundwater flow ensembles. The algorithm decouples the system into two subphysics problems and allows larger time steps in the porous media region while using smaller time steps in the free flow region. We also adopt an artificial compressibility technique to further decouple the computation of the velocity and the pressure for which the pressure can be updated directly without solving a Poisson equation. The ensemble algorithm results in a common coefficient matrix for all realizations of different samples, consequently allows the use of efficient direct or iterative solvers to reduce the computational cost. We provide comprehensive stability analysis for both the nonensemble and the ensemble algorithms. Our numerical experiments illustrate the algorithm is second‐order convergent and the ensemble scheme reduces the computational time of the nonensemble counterpart by 96%. A realistic numerical experiment on a curvy domain is also presented. [ABSTRACT FROM AUTHOR]

This paper focused on regional climate change impacts on hydro-meteorological variables in the Upper Chao Phraya River basin located in northern Thailand. The five global climate models were used with a number of 15 experiments to assess near future water resources over the period 2026-2040. The impacts of climate change were quantified in percentages relative to a retrospective period (1986- 2000). On average, the surface temperature tends to increase by 1.45, 1.48, and 1.80 °C under the lowest (RCP2.6), intermediate (RCP4.5), and highest (RCP8.5) CMIP5 greenhouse gas emission scenarios, respectively. Mathematical model called H08 was used, the coupling of three modules did a very good job on mimicking river discharge with high Nash-Sutcliffe and Index of Agreement. The projections of rainfall and its response to surface runoff and groundwater recharge exhibit relatively uneven distributions. The upper basin tends to face extremely heavy rainfall and taking place of serious flood, while the lower areas are expected to cope with drought. Based upon ensemble averages over the entire area, relative changes of -1.7% (-6.4%), -0.1% (-5.2%), and -2.0% (-9.3%) in the mean annual rainfall (groundwater recharge) are shown under the RCP2.6, RCP4.5, and RCP8.5 scenarios, respectively. This study included a groundwater recharge assessment indicating potential available groundwater use, which is considered to be a key resource for climate change adaptation. Based on these findings, implementing such an artificial groundwater recharge system is needed in order to harvest surplus water and making for coping with water stress in the dry season. [ABSTRACT FROM AUTHOR]

The dependence of human beings on groundwater and ever-increasing demands of growing population, agriculture and industries, has resulted in its over-exploitation. This has led to the decline of groundwater levels and its shortage especially in lean season. The study area, Reodar block of Sirohi district, Rajasthan, is an over-exploited block with the stage of groundwater extraction at 159% and has an average declining water level trend at the rate of 0.24 m/year. Artificial recharge was proposed in the study area through the construction of recharge shafts and injection wells, after delineating the weathered thickness in the submergence area of existing ponds and check dams of the study area by carrying out vertical electrical sounding (VES). In all, VES were conducted at 178 sites and recharge structures were constructed at 76 out of 109 scientifically selected sites with suitable weathered thickness and attempt was made to establish their impact on water levels through pre-monsoon water level monitoring. The comparison of pre-monsoon water level observations spanning over four decades reveals its spatio-temporal decline in the study area. The construction of these recharge structures has resulted in significant increase in area from 38% to 68%, under 0 to 20 m below ground level water level range. This study demonstrates the importance of resistivity surveys in scientifically selecting the suitable sites for construction of recharge structures and significance of long-term water level monitoring in assessing the groundwater scenario and impact assessment, in poorly characterized hydrogeological areas. [ABSTRACT FROM AUTHOR]

The sustainable water initiative for tomorrow (SWIFT) is a 378,000 m3/day (100 MGD) managed aquifer recharge (MAR) program designed by the Hampton Roads Sanitation District (HRSD) to rehabilitate the Potomac Aquifer System (PAS) in the Coastal Plain of Eastern Virginia. Groundwater is a primary water source in Eastern Virginia with over 93% of reported use derived from the PAS. Starting in May 2018, HRSD has operated a 3780 m3/day (1.0 MGD) MAR demonstration facility at the SWIFT Research Center (SWIFT‐RC) in Suffolk, Virginia. The primary aim of the SWIFT‐RC is to demonstrate, at a meaningful scale, the feasibility of MAR using deep well recharge into confined PAS hydrostratigraphic unit. The SWIFT‐RC employs advanced water treatment technology to bring secondary effluent from an HRSD wastewater treatment plant to drinking water standards. Lessons learned include the evaluation and selection of a multiple barrier carbon‐based treatment system to ensure water quality and maintain geochemical compatibility between MAR water and native groundwater, and the evaluation and selection of aluminum chlorohydrate for stabilizing aquifer clays immediately around the well to accept the fresher recharge water. The distribution of flow in the SWIFT‐RC multiscreen recharge well and associated well injectivity were variable with time resulting from changing conditions in the well. Dynamic recharge well performance was quantified through the combined analysis of intrinsic and artificial tracer transport, in situ flowmeter testing, and water level analysis. Monitoring well nests and a depth‐discrete sampling system supported a robust sampling plan to analyze chemical transport and attenuation in SWIFT‐RC groundwater. Article impact statement: SWIFT demonstrates the use of advanced water treatment and recharge wells for aquifer rehabilitation in a coastal plain confined aquifer. [ABSTRACT FROM AUTHOR]

Kuwait, an arid country, wants to have a reserve of water for emergency use and has planned to create an underground reserve of water through multi‐well artificial recharge at Kabd area. Numerical modeling of different recharge–recovery scenarios was carried out to chalk out an optimum strategy for implementation of the project. These scenario runs suggested that apart from the aquifer parameters and the quality of the groundwater and the recharge water, the well spacing and well construction, orientation of the field with respect to the prevailing hydraulic gradient, and the injection and the pumping schedule would determine the overall recovery efficiency of the setup. For the selected site, following strategies were found to have positive impact on meeting the goals of the creation of a reserve of water for use in an emergency: (1) during the reserve creation stage, simultaneous recharge and pumping through alternate wells; (2) the compensation of the water lost from the reserve created due to the flow down the hydraulic gradient during the waiting period; and (3) the orientation of the long axis of the field perpendicular to the regional hydraulic gradient. The adoption of cyclic injection and recovery option for the creation of the reserve eliminates the need of the first two steps but calls for several cycles of injection followed by recovery and adequate and consistent supply of water for injection over that period. An optimum field design and two alternative recharge options have been suggested based on the above observations. Article impact statement: The article highlights the importance of field design and operation plan on recovery efficiency of a multi‐well artificial recharge system. [ABSTRACT FROM AUTHOR]

Drought and water scarcity can significantly impair the sustainable development of groundwater resources, a scenario commonly found in aquifers in the Mediterranean region. Water management measures to address these drivers of groundwater depletion are highly relevant, especially considering the increasing severity of droughts under climate change. This study evaluates the potential of managed aquifer recharge (MAR) to offset the adverse effects of drought and water scarcity on groundwater storage. Los Arenales aquifer (central Spain), which was unsustainably exploited for irrigation in the second half of the twentieth century, is employed as a case study. Two neighbouring zones within this aquifer are contrasted, namely, Los Arenales (LA) and Medina del Campo (MC). The primary difference between them in terms of water resources management is the wide-scale implementation of MAR systems in LA since the early 2000s. Several groundwater statistical methods are used. Groundwater-level trend analysis and average piezometric levels show in LA a faster recovery of aquifer storage and less susceptibility to drought compared to MC. On the other hand, standardised precipitation indexes and standardised groundwater level indexes of detrended groundwater-level time series, which do not include the effects of MAR, show that LA can be more negatively affected by drought and groundwater abstraction. The sharper recovery of piezometric levels in LA when considering MAR, and bigger drought impacts observed when the effects of this measure are removed, demonstrate that MAR can effectively alleviate the impacts of water scarcity and drought, providing an adaptation solution to climate change worldwide. [ABSTRACT FROM AUTHOR]

Accurate identification of groundwater potential areas in arid regions is an important task for groundwater management and sustainability. As a result, this study used the innovative integration of remote sensing (RS), geographic information system (GIS), watershed modeling system (WMS), geophysical survey, and water mass balance equation to identify potential groundwater areas in the W. Dara, Eastern Desert, Egypt. A weighted spatial probability model (WSPM) of groundwater potential based on eight regulatory factors was implemented within ArcGIS software. Drainage density (DD), precipitation (P), net groundwater recharge (NGR), terrain slope (TS), lineament density (LD), lithologic group (LG), water quality (TDS), and depth to groundwater level (DGW) are the aspects considered. The Analytical hierarchy process (AHP) method was used to assign weights to these parameters, and their accuracy was estimated using the consistency ratio (CR). The resulting groundwater potential map classified W. Dara study area into five categories, ranging from very low to very high potential. A geophysical survey, in the form of Vertical Electrical Sounding (VES) and Transient Electromagnetic (TEM), was conducted along W. Dara to validate the results of the WSPM, which identified areas of high groundwater potential. The 1D inversion of VES/TEM shows that the central and western parts of W. Dara are considered the most promising areas for groundwater occurrence, and are located in areas of high and very high potential classes derived from WSPM. Moreover, the results of VES and TEM surveys showed that the proposed aquifers (Nubian Sandstone, Miocene, and Quaternary) in the study area are horizontally and vertically connected through a set of normal faults traversing NW-SE. Ten sites have been proposed for drilling additional exploitative wells in W. Dara area based on the WSPM and geophysical survey with the aim of sustainable development. Thus, the integrated techniques applied in this study proved effective in accurately determining the development strategy for arid and semi-arid coastal areas, especially those that suffer from scarcity of rainfall and increased agricultural reclamation requirements in remote areas. [Display omitted] • RS, GIS, WMS, and geophysical surveys crucial for arid groundwater sustainability. • Recommended drilling of 10 wells in high-potential areas. • Proposed rock dams enhance groundwater recharge from floodwaters. • Integrated tools boost water resource management in arid regions. [ABSTRACT FROM AUTHOR]

Monitoring and assessing groundwater quality and quantity lays the basis for sustainable management. Therefore, this research aims to investigate various factors that affect groundwater quality, emphasizing its distance to the primary source of recharge, the Nile River. To this end, two separate study areas have been considered, including the West and West-West of Minia, Egypt, located around 30 and 80 km from the Nile River. The chosen areas rely on the same aquifer as groundwater source (Eocene aquifer). Groundwater quality has been assessed in the two studied regions to investigate the difference in quality parameters due to the river's distance. The power of machine learning to associate different variables and generate beneficial relationships has been utilized to mitigate the cost consumed in chemical analysis and alleviate the calculation complexity. Two adaptive neuro-fuzzy inference system (ANFIS) models were developed to predict the water quality index (WQI) and the irrigation water quality index (IWQI) using EC and the distance to the river. The findings of the assessment of groundwater quality revealed that the groundwater in the west of Minia exhibits suitability for agricultural utilization and partially meets the criteria for potable drinking water. Conversely, the findings strongly recommend the implementation of treatment processes for groundwater sourced from the West-West of Minia before its usage for various purposes. These outcomes underscore the significant influence of surface water recharge on the overall quality of groundwater. Also, the results revealed the uncertainty of using sodium adsorption ratio (SAR), Sodium Percentage (Na%), and Permeability Index (PI) techniques in assessing groundwater for irrigation and recommended using IWQI. The developed ANFIS models depicted perfect accuracy during the training and validation stages, reporting a coefficient of correlation (R) equal to 0.97 and 0.99 in the case of WQI and 0.96 and 0.98 in the case of IWQI. The research findings could incentivize decision-makers to monitor, manage, and sustain groundwater. • Data was collected from two areas that were different from the river. • Physiochemical analysis for 296 samples has been performed. • Hydrogeochemical facies and dynamics have been investigated. • Groundwater appropriateness for various purposes has been evaluated. • ANFIS Model has been developed to predict WQI and IWQI. [ABSTRACT FROM AUTHOR]

• U-Net accurately reproduces the groundwater response to artificial recharge. • Inputs include properties of the first aquifer, drainage network, and recharge rate. • Transmissivity and surface water networks significantly impact the response. • U-Net representing a 3000-fold speed up compared to gridded groundwater model. • Minor benefits from more than 500 recharge sites for training. Groundwater models are a valuable tool in optimising the decisions influencing groundwater flow. Spatially distributed models represent the groundwater level in the entire area from where essential information can be extracted, directly aiding in the decision-making process. However, these models are time-consuming, limiting the number of scenarios that can be considered. This study explores different machine learning (ML) models as faster alternatives to predict the increase in steady-state groundwater head due to artificial recharge in the unconfined aquifer while considering a wider spatial extent (832 columns x 1472 rows totalling 765 km2) than previous ML groundwater models. We trained three ML models (encoder-decoder, U-Net, and attention U-Net) with various hypothetical artificial recharge sites (100, 300, 500, and 1000 sites) in the Baakse Beek catchment (the Netherlands), using a detailed numerical groundwater model, AMIGO. The applied recharge rate along with geo-hydrological properties from the AMIGO baseline run were used as inputs to the ML models. The properties' permutation importance indicated that all properties of the first aquifer were important to predicting the response and were included when training the ML models. All three ML models improved with additional training sites but showed limited benefits from more than 500 recharge sites. Of the three ML models, U-Net and Attention U-Net outperformed the encoder-decoder. These two models achieved Nash-Sutcliffe efficiency (NSE) of more than 0.8 when trained with 300 or more recharge sites. U-Net trained on 1000 recharge sites had the highest overall NSE of 0.95. U-Net better captures input features with highly variable spatial characteristics, such as rivers and drains which influence the maximum height of the groundwater response. The model captured the influence of the input features on the response, reproducing the response patterns across the entire catchment. Finally, we showed that the trained ML models are faster than the numerical model, predicting within 0.24 s (97th percentile), making it ideal for optimising decisions. [ABSTRACT FROM AUTHOR]

• Interactions between surface water and groundwater were determined though an integrated method; • Impacts of artificial recharge on groundwater quantity and quality were quantified; • The main factors controlling regional groundwater quantity and quality were found; • Suggestions for artificial recharge and groundwater management were given. Artificial groundwater recharge is increasingly utilized globally for addressing regional groundwater issues due to its effectiveness and ease of application. However, due to the complexity of the interaction of groundwater systems with the external environment and its inherent latency, governance effects are difficult to quantify and are not fully understood yet. In this study, the efficiency of areal artificial groundwater recharge was determined and the interactions with surface water were analyzed by field surveys, sample analysis, water balance reconstruction, and model simulation. A typical groundwater recharge region in the Beijing-Tianjin-Hebei region, China, was focused. Additionally, the response of groundwater flow and water quality to areal artificial groundwater recharge was quantified. Results showed that areal artificial groundwater recharge changes the relationship between surface water and groundwater, with an efficiency of 70 % under high recharge and fluctuation, and decreasing to 20–30 % after the groundwater level was stabilized. The impact on the hydrodynamic field were primarily manifested as the formation of water mounds near river channels, which expand laterally up to 9.2 km from the recharging river channel one year after implementation.Then the impact increases to 14.9 km and continues to expend a year after cessation. The areal artificial groundwater recharge has simultaneously improved the water quality by 23 % in monitoring wells within a 10 km distance from the river channel. The results of this study quantify the impacts of area artificial recharge on groundwater and provide references for the improvement of water resources and water environment in those similar regions. [ABSTRACT FROM AUTHOR]

• A new groundwater tritium and carbon isotope dataset is established for China. • The time series of the precipitation 3H and atmospheric 14C are reconstructed for China. • The depth profiles of modern groundwater and fossil groundwater in China are presented. • In China, fossil groundwater is dominated (>50 %) in most wells (>50 %) below 300 m. • In China, precipitation after 1953 can hardly recharge groundwater below 420 m. Older groundwater is generally more susceptible to overdraft and also more difficult to recover once contaminated. To understand the prevalence and vulnerability of fossil groundwater infiltrated before Holocene, a global assessment has been conducted recently, but the analysis results for China have been limited by the collection of data. In this study, we combined the groundwater isotope data from the literature databases of CNKI (China national knowledge infrastructure) and SCIE (Science citation expanded) and established the groundwater age dataset of China by virtue of the water samples from 1441 wells. By reconstructing the historical precipitation 3H records of China and using the late-Quaternary atmospheric 14C, the fractions of the modern groundwater that infiltrated after the year 1953 and the fossil groundwater that infiltrated before 12,000 years in the groundwater samples have been calculated based on the straight-forward mixing models. Then we evaluated the extent and depths of the modern and fossil groundwater in the major 16 groundwater-supply areas of China. The results show that the exploitation of deep groundwater mainly occurs in northern China, such as in the Ordos Basin, the North China Plain, and the Hexi corridor, etc. The average critical depth of the vertical transition zone between modern infiltration water and fossil groundwater in China is about 300 m, beneath which more than half of the water samples are dominated by fossil groundwater. Meanwhile, at depth greater than 420 m, the groundwater can rarely be recharged by the modern precipitation. Besides, in China, modern and fossil groundwater, respectively, share 15–45 % and 20–85 % of the total groundwater storage in the uppermost 1000 m of the crust. [ABSTRACT FROM AUTHOR]