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Many communities around the world rely heavily on groundwater for drinking, cooking, washing and irrigation. Sadly, continuing unfettered pumping and withdrawal of groundwater from Pleistocene aquifers have risked high-arsenic groundwater being drawn from adjacent upper Holocene aquifers. Experts have warned that arsenic pollution (particularly of AsIII species) in groundwater poses serious health hazards in several countries where millions of people drink and use arsenic-contaminated water. Due to arsenic-related health concerns in many parts of the world, there is a realization of the need to find solutions for remediating contaminated aquifers and/or groundwater including methods to stabilize arsenic in the soils and rocks. In light of this, a review is undertaken in this paper of the in-situ treatment technologies being investigated to remove arsenic from groundwater, in both laboratory and field settings. Discussion and analysis of the main categories of in-situ treatment methods include (1) passive reactive barriers (PRB) with removal techniques involving surface precipitation and sorption, chemical reactions and reactions with biological mechanisms, (2) chemical oxidation by delivering iron salts and oxidants into aquifers, (3) injection of adsorbent, (4) biological treatment, and (5) artificial recharge. Materials used for PRB technique studies, reactants used for oxidation techniques and parameters influencing the efficiency of the remediation using artificial recharge are also summarized. [ABSTRACT FROM AUTHOR]

Countries face challenges of excess, scarcity, pollution, and uneven water distribution. This study highlights the benefits of advances in groundwater engineering that improve the understanding of utilizing local geological characteristics due to their crucial role in resisting drought in southern Lebanon. The type of drought in the region was determined using the Standardized Precipitation Index (SPI), Standardized Vegetation Index (NDVI), Vegetation Condition Index (VCI), and Soil Moisture Anomaly Index (SM). The dry aquifer and its characteristics were analyzed using mathematical equations and established hydrogeological principles, including Darcy's law. Additionally, a morphometric assessment of the Litani River was performed to evaluate its suitability for artificial recharge, where the optimal placement of the water barrier and recharge tunnels was determined using Spearman's rank correlation coefficient. This analysis involved excluding certain parameters based on the Shapiro–Wilk test for normality. Accordingly, using the Geographic Information System (GIS), we modeled and simulated the potential water table. The results showed the importance and validity of linking groundwater engineering and morphometric characteristics in combating the drought of groundwater layers. The Eocene layer showed a clearer trend for the possibility of being artificially recharged from the Litani River than any other layer. The results showed that the proposed method can enhance artificial recharge, raise the groundwater level to four levels, and transform it into a large, saturated thickness. On the other hand, it was noted that the groundwater levels near the surface will cover most of the area of the studied region and could potentially store more than one billion cubic meters of water, mitigating the effects of climate change for decades. [ABSTRACT FROM AUTHOR]

To keep groundwater levels stable, Jinan's government has implemented several water management measures. However, considerable volumes of dissolved organic carbon (DOC) can enter groundwater via water exchange, impacting groundwater stability. In this study, a SWAT-MODFLOW-RT3D model designed specifically for the Yufu River Basin is developed, and part of the code of the RT3D module is modified to simulate changes in DOC concentrations in groundwater under different artificial recharge scenarios. The ultimate objective is to offer valuable insights into the effective management of water resources in the designated study region. The modified SWAT-MODFLOW-RT3D model simulates the variations of DOC concentration in groundwater under three artificial recharge scenarios, which are (a) recharged by Yellow River water; (b) recharged by Yangtze River water; and (c) recharged by Yangtze River and Yellow River water. The study shows that the main source of groundwater DOC in the basin is exogenous water. The distribution of DOC concentration in groundwater in the basin shows obvious spatial variations due to the influence of infiltration of surface water. The area near the upstream riverbank is the earliest to be affected. With the prolongation of the artificial recharge period, the DOC concentration in groundwater gradually rises from upstream to downstream, and from both sides of the riverbank to the surrounding area. By 2030, the maximum level of DOC in the basin will exceed 6.20 mg/l. The Yellow River water recharge scenario provides more groundwater recharge and less DOC input than the other two scenarios. The findings of this study indicate that particularly when recharge water supplies are enhanced with organic carbon, DOC concentrations in groundwater may alter dramatically during artificial recharge. This coupled modeling analysis is critical for assessing the impact of recharge water on groundwater quality to guide subsequent recharge programs. [ABSTRACT FROM AUTHOR]

As stormwater management embarks on a new journey of resource allocation and disparity, addressing the contamination resulting from deicing salts is a growing concern for designers and land planners. Turf and native grass variety are currently one of the most readily available and adaptive resources to address some of these ever increasing hydrologic concerns. However, little is known about the water quality efficiency and optimal design layout of turf and native grasses in urban or rural landscapes with regards to salt remediation. In this study, a five plot series of grass swales was utilized in this study to measure water quality efficiency and salt tolerance of turf and native grasses. The grass varieties that were tested in this study include; Common hard fescue (Festuca trachyphylla), Chewings fescue (Festuca rubra commutata), and sheep fescue (Festuca ovina). Results showed that the grass swales that made up of a blend of grass variety were the most successful at reducing saline and TDS levels as compared to their monoculture counterparts. The findings reveal that a relatively simple grass swale could provide excellent salt and TDS reduction when utilizing a blend of grass varieties; specifically a hard fescue and sheep fescue blend. [ABSTRACT FROM AUTHOR]

Introduction and GoalThe aquifer recharge rate is one of the most difficult items to measure in GW resource evaluation. The techniques used in quantifying recharge are categorized in three main groups: unsaturated zone, saturated zone and surface water techniques. The saturated zone method is devided into physical methods (including Darcy's law and tracers), numerical modeling (the purpose of this research), groundwater level fluctuations, and water balance.Materials and methods Hydres and LitchW models were used to simulate soil moisture movement to simulate aquifer recharge in this study. The models were then calibrated by optimizing the water flow factors of the aquifer layers in the Gareh Bygon with the inverse solution method. The water characteristics of the unsaturated soil layer in three wells with an approximate depth of 30 m in one of the floodwater spreading basins were measured by field and laboratory methods. The soil moisture measuring device, TDR, was calibrated for the stony soils of the research area The sensors are then placed in holes with insulated walls from the surface to the depth.walls of oneof the wells Amount of soil-water contents were continuously measured from Sep. 2010 to Sep. 2020. The height of floodwater inundation and rainfall were also recorded. Recharge through unsaturated layers was assessed based on the soil water balance method as the observed data set.Results and discusionValidation flow simulation results from the of Hydrus and LEACHW models with observed measurements. The results showed that the Hydrus and LEACHW model very accurately estimated the water flow after the flood event (R2 and RMSE equal to 0.994 and 45.3 cm respectively in Hydrus model and 0.993 and 37.11 cm in LEACHW, respectively). In addition, the results of the Hydrus model were closer to measurements. The discharge ratio (the amount of infiltration divided by the amount of flood + precipitation) in the three methods of soil water balance, the Hydrus model and the LEACHW model were 47, 44 and 52 respectively, with an average of 48 for all flood events and 75, 71 and 92 with an average of 80% for large flood events. In the event of precipitation without flooding, practically all precipitation was spent on evaporation-transpiration, and for this reason, the size of the average infiltration ratio decreased in all events.Conclusion and recommendationValidation simulated flow results with Hydrus and LEACHW were compared with the observed measurements, demonstrating that these models accurately estimated the water flow after the flood event. In addition, , the results of the Hydrus model were closer to measurements. The mean data of the LEACHW and Hydrus models were overestimated by approximately 5 units less than 1 unit respectively. In simulations of water movement in soil using models such as Hydrus, a certain amount of water conductivity for the entire vertical column of the soil profile commonly considered. The results of this research showed how unrealistic such an assumption is. Therefore, in multi-layer soils, special attention should be given to the difference between layers and the use of water conductivity estimation equations. For the researched area, one-dimensional Hydrus model was recalibrated and its validation results were completely acceptable. This model can be used in three-dimensional mode for larger areas as a tool for applying different scenarios to manage the floodwater spreading system and increase their efficiency.

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]

A sustainable approach is proposed for managing the effects of salinity ingression in Salalah coastal aquifer, Oman. This paper aims to analyze and compare the groundwater levels and salinity of the aquifer from 1993 to 2027, considering both predictive and actual transient scenarios. Two novel scenarios were proposed, established, and examined in this study to bring back the aquifer to steady-state condition. The first scenario entails ceasing groundwater pumping from both Salalah and Saada wellfields, while compensating for the groundwater supply from these sources with surplus desalinated water. This scenario is projected to occur during the predictive period spanning from 2023 to 2027, denoted Scenario A. The second scenario is business as usual and involves continuing pumping from both wellfields during the same predictive period, denoted Scenario B. A numerical model for 3D flow simulation and advective transport modeling showed that on the eastern side of the Salalah coastal aquifer, the extent of seawater intrusion (SWI) was identified stretching from the shoreline to a distance of 1800 m, 1200 m, 0 m, and 600 m, in years 2011, 2014, 2018, and 2022 under the transient period, whereas SWI was delineated in land up to 0 m and 700 m in the predictive year 2027 under Scenarios A and B, respectively. In the western side of Salalah coastal aquifer, SWI was delineated in land up to 2000 m, 1700 m, 0 m, and 800 m, in years 2011, 2014, 2018, and 2022 under the transient period, whereas SWI was delineated in land up to 0 m and 750 m in the predictive year 2027 under Scenarios A and B, respectively. This study claims that Scenario A effectively pushed the seawater interface back to the coastline, projecting its reach to the shoreline (0 m) by 2027. In contrast, in baseline Scenario B, the wedge of saline intrusion in the Salalah coastal aquifer was delineated from the shoreline, up to 800 m inland, which accounted for continuation of pumping from both wellfields during the predictive period. The study concludes that Scenario A has the capability to efficiently reduce the impact of saline inflows from the coast, while Scenario B results in a more pronounced impact of salinity intrusion. [ABSTRACT FROM AUTHOR]

The present study attempts to delineate groundwater zones using multi-criteria decision analysis based on land-use/cover pattern, groundwater table, and groundwater quality for both domestic and agricultural use in the Bist-Doab region of Punjab, India. The region has about 71% land under agricultural activities, 12% under built-up area, 7% under forest cover, 5% under tree plantation, 3% under water bodies, and the remaining 2% under open area. As far as the groundwater table is concerned, about 8% of the region has a groundwater table below 30 m, mainly around the urban areas of Jalandhar. Qualitatively, the groundwater has not been found suitable for domestic consumption in areas around Jaijjon, Taunsa, Jalandhar urban agglomeration, Shahkot, and Nakodar blocks. In 10% of areas of Sultanpur Lodhi, Shahkot, Nakodar, Phagwara, and Bhulath, the groundwater has been found unsuitable for irrigation. The groundwater zoning resulting from the stacking of these thematic layers reveals that about 20% of the region has a poor quality of groundwater, mainly occupying the areas of urban agglomeration of Jalandhar, Phagwara, Hoshiarpur, parts of Sultanpur Lodhi, Mahilpur, and Balachaur blocks. In the urban cluster of Jalandhar, Phagwara, and Hoshiarpur, a high level of urbanization and industrialization is responsible for the poor quality of groundwater. The untreated discharge of industrial wastes from pharmaceutical companies is responsible for poor quality of groundwater in the Balachaur block of Shaheed Bhagat Singh Nagar district. Further, the groundwater of the remaining 80% of the region is of better quality, but that too is vulnerable to groundwater deterioration due to various anthropogenic factors, such as higher groundwater extraction, intensive application of chemical fertilizers in the fields, and prevailing cropping pattern. The study suggests certain groundwater management strategies, viz. comprehensive planning of land-use/cover pattern, change in cropping pattern, change in prevailing agricultural practices such as water-saving irrigation, shift to rain-fed irrigation, minimum use of chemical fertilizers, promotion of organic farming, treatment of urban and industrial wastes, rainwater harvesting, artificial recharge, regular monitoring, legal restriction on water use, and energy pricing, which can be efficient in dealing with the emerging problems of groundwater resources in the region. [ABSTRACT FROM AUTHOR]

In the Ferkla Oasis, much like in numerous other oases across the southeastern region of Morocco, a range of socioeconomic and environmental challenges are intricately linked to the inadequate management of water resources. One proposed remedy to address these concerns is the implementation of artificial aquifer recharge, which stands as an alternative strategy to safeguard the crucial oasis ecosystems. Thus, to evaluate the viability of this method in promoting sustainable water resource usage, it becomes imperative to delineate groundwater recharge potential zones (GRPZs). This study aims to achieve this objective by mapping GRPZs within the Ferkla Oasis, employing a fusion of the analytical hierarchy process (AHP), geospatial information derived from remote sensing (RS), and geographic information system (GIS) technologies. In pursuit of this goal, an array of geological, topographical, pedological, hydrological, and climatic criteria have been meticulously selected, classified, and assigned weights following their relevance to water infiltration suitability. This comprehensive approach culminates in the generation of seven thematic maps: slope, lineament density, lithology, soil type, drainage density, land use/land cover, and rainfall distribution. Through the integration of these aforementioned maps, a tripartite classification of potential GRPZs emerges, comprising low, medium, and high categories. The findings underscore the distribution: 30% of the total study area exhibits a low potential for GRPZs, 50% of the total land area is characterized as having medium potential GRPZs, while the remaining 20% is designated as high potential GRPZs. These outcomes have been substantiated through validation against piezometric levels, which have been ascertained through recent field surveys. Consequently, these results stand as a testament to the efficacy of the presented approach as a robust decision-making tool. The approach effectively facilitates the establishment of conditions conducive to viable artificial recharge, thereby offering a means to safeguard the groundwater reservoirs that sustain the fragile oasis environments. [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]

1- Introduction One of the important purposes of flood spreading plans is to feed groundwater tables and increase quality of these resources. One of the most important indicators for evaluation of artificial recharge plans is to examine their impact on quality of groundwater resources. The main aim of current research is to investigate effects of implementation of artificial aquifer recharge plan (Herat flood spreading) on temporal changes of groundwater quality parameters in the region. 2- Methodology Harat watershed area is 1413 square kilometers in south of Yazd province. The location of flood spreading sites implemented at the end of Harat basin outlet and with an area of 490 hectares, which includes four implementation areas. In order to investigate and evaluate the effects of flood spreading projects on groundwater resources, statistics of parameters of 17 wells were used from the area of aquifer of Fathabad affected by these projects, based on available information, parameters of calcium, carbonate, magnesium, sodium, chlorine, and total dissolved solids and salt was extracted. The wells were classified into two groups, control and affected, based on their location relative to sites and the direction of flow in waterways of area. According to length of period, in order to evaluate the impact of water withdrawals and consequently impact of sedimentation on the efficiency of the sites, the entire period was divided into two periods so that 2003-2011 is first period and 2012-2021 is second period. Minitab software was used to check linear trend of average groundwater quality parameters. For this purpose, the average of all types of quality parameters of water resources, first and second periods were entered in software and the change process for each parameter was obtained. In order to investigate temporal trend of groundwater quality parameters, Mann-Kendall test was used at 95% confidence level and Sen's slope by XLSTAT 2019 Software. 3- Results The results related to time trend of water quality factors through Mann-Kendall method and Sen's slope showed that calcium factor among nine wells located downstream of the project, three wells have no trend and the rest have a negative trend. The results of checking trend of control wells showed that calcium had a positive trend in all but one well during statistical period under review. Factors of sodium, bicarbonate and magnesium in the downstream of projects often have a negative trend and also in the control area they often show a positive trend, but factors of salinity, chlorine and total dissolved solids in the control area do not have the same situation as other factors. So that the number of wells without trend in the control range is more than the rest of the factors. This means that the condition of the aquifer in terms of three indicators is neutral and does not have a negative or positive tendency, but the investigation of trend related to affected area showed that flood spreading projects have been able to improve the status of these factors, which are part of the important factors affecting agricultural water. lead to improvement. In order to investigate effects of flood spreading projects, at the beginning and after several years, linear trending of the average factors was done in two time periods. Due to lack of data in the last of years of implementation of flood spreading to evaluate effectiveness of groundwater quality from flood spreading project, the number of available years was divided into two almost equal parts so that impact of these projects can be investigate in the initial period and after a few years. The results of linear trend of the first and second periods showed that total dissolved solids and calcium were decreasing with a high slope in the first period, but in second period and after a few years, effectiveness decreased, but it is still decreasing with a gentle slope. Bicarbonate and magnesium factor have had an increasing trend in first period, and in second period, magnesium has decreased towards a negative slope, but bicarbonate follows an increasing trend with a higher slope than in first period. In the case of other factors such as salinity, chlorine, sodium, trends are almost similar to each other. So, in the first period, they have decreased with a slight slope, but in second period, this slope has increased proportionally. This means that the infiltration of flood water through these projects has been able to improve status of all factors except for bicarbonate, but the passage of time has left different effects on the manner and extent of effect, which requires more detailed investigations. 4- Discussion & Conclusions According to results of investigations of time trend of various factors in this region, flood spreading has been able to have a positive effect on quality of groundwater. So that in determining trends of whole aquifer, except for bicarbonate factor, which had a positive trend, in other factors, there was a decreasing trend and no trend, which indicates positive effect of flood spreading on the control of quality factors. The results of this research showed that state of trend of all factors in some wells of witness area showed an increase and, in some wells, there was no trend, but in the affected area (downstream) all factors had a decreasing trend. The location of wells and distance from the waterways and flood spreading sites have a great impact on the vulnerability of wells. So that B9 well, which is located in the farthest part of the affected aquifer and is far from flood spreading sites, is among wells that had the most negative trend in most factors. Also, B3 and B2 wells are among wells that have the highest decreasing slope. Investigations showed that B9 well was located at a very short distance from the main waterway and B2 and B3 wells are also located near the distribution sites in addition to position relative to waterway and are affected by several flood distribution sites. So, distance of wells from waterway and the location of the sites can be very effective. [ABSTRACT FROM AUTHOR]

Countries face challenges of excess, scarcity, pollution, and uneven water distribution. This study highlights the benefits of advances in groundwater engineering that improve the understanding of utilizing local geological characteristics due to their crucial role in resisting drought in southern Lebanon. The type of drought in the region was determined using the Standardized Precipitation Index (SPI), Standardized Vegetation Index (NDVI), Vegetation Condition Index (VCI), and Soil Moisture Anomaly Index (SM). The dry aquifer and its characteristics were analyzed using mathematical equations and established hydrogeological principles, including Darcy’s law. Additionally, a morphometric assessment of the Litani River was performed to evaluate its suitability for artificial recharge, where the optimal placement of the water barrier and recharge tunnels was determined using Spearman’s rank correlation coefficient. This analysis involved excluding certain parameters based on the Shapiro–Wilk test for normality. Accordingly, using the Geographic Information System (GIS), we modeled and simulated the potential water table. The results showed the importance and validity of linking groundwater engineering and morphometric characteristics in combating the drought of groundwater layers. The Eocene layer showed a clearer trend for the possibility of being artificially recharged from the Litani River than any other layer. The results showed that the proposed method can enhance artificial recharge, raise the groundwater level to four levels, and transform it into a large, saturated thickness. On the other hand, it was noted that the groundwater levels near the surface will cover most of the area of the studied region and could potentially store more than one billion cubic meters of water, mitigating the effects of climate change for decades.

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. HIGHLIGHTS For groundwater artificial recharge, GWRP zones are the primary factors to be mapped.; Satellite images and the GIS proved to be reliable tools for the assessment of GWRP zones.; Multicriteria data analysis is required to integrate the controlling factors in GWR.; Rocks’ lithology is the most influencing factor on GWR.; More than 75% of the Riyadh Region is characterized by low-to-very low GWR.;

The Cheria region in Northeastern Algeria has been facing aquifer overexploitation by the agricultural sector and prolonged droughts, resulting in a considerable decline in groundwater levels. This study investigates the feasibility of implementing artificial recharge techniques to replenish the Eocene aquifer which serves as the primary water source in the Cheria region. A 3D transient numerical model, based on the finite difference method, was used to simulate groundwater flow from 2021 to 2031 using Visual MODFLOW Flex. During the modelling process, three scenarios were considered: (1) including pumping without a recharge, (2) recharge of the entire area through efficient infiltration without pumping, and (3) artificial recharge using river water infiltration basins at two sites, Draa Douamis sinkholes and Eocene limestone outcrops. The simulation results showed that aquifer exploitation without recharge caused significant drawdowns, which were 3 m to 7 m in the north-eastern part and 8 m to 12 m in the central and southern parts. In contrast, the second scenario, involving recharge without pumping, showed a rise in groundwater levels of 2 m to 2.7 m in the north-eastern part and 3 m to 3.62 m in the central and southern parts. The third scenario, employing artificial recharge, indicated a positive response to artificial recharge, with increased piezometric levels at the proposed sites, signifying a beneficial impact on the aquifer. These findings underline the potential of artificial recharge as a promising approach to address the groundwater depletion and environmental issues in the Cheria Basin.

The Agua Amarga salt marsh has been subjected to artificial seawater recharge on its surface during the period 1925–1969 for industrial purposes (saltwork activity) and from 2008 to present to compensate for coastal groundwater abstraction to supply Alicante desalination plants. This groundwater abstraction has caused piezometric depletion in the coastal aquifer connected to the protected salt marsh. The seawater recharge program also involved vegetation monitoring to control the impact on the salt marsh ecosystem, allowing data to be collected about the halophyte vegetation species growing in the salt marsh (Arthrocnemum macrostachyum, Sarcocornia fruticosa, and Ruppia maritima, among others) from spring and autumn field surveys. In this work, vegetation development is assessed with remote sensing for the period 1929–2022 using images with visible and near-infrared spectral resolution. Different spectral indices (NDVI, BI, and NDWI) and classification algorithms (random forest) are used to calculate the vegetation cover. Field data are employed to evaluate the protocols and compare the results, showing a 46% decrease caused by the salt works and a 50% increase as a result of natural evolution and artificial recharge. The spread of Phragmites australis is also addressed by comparing LiDAR data with field monitoring, showing an increase of 12% during the period 2005–2023. The advantages and complementarity of field monitoring and remote sensing information are explained. [ABSTRACT FROM AUTHOR]

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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.

Past hydrogeological processes and human impacts may exert substantial memory effects on today’s groundwater systems. Thorough characterization of such long-term processes is required for scientists and policymakers to predict the hydrogeological impacts of land management options. Especially in data-scarce areas, historical data are essential to unravel long-term hydrogeological processes, which could not be identified by short-term fieldwork or model simulations alone. However, historical data are often overlooked or only used as background information in most hydrogeological studies. We show that the combination of historical reports and quantitative data yields major insights in the hydrogeological system of Curaçao, a small semi-arid Caribbean island. Reconstructing the island’s groundwater conditions over the past 500 years revealed that deforestation and excessive abstraction has had a detrimental effect on the island’s groundwater reserves. Historical notes and data revealed major signs of seawater intrusion, especially during abstraction peaks in the island’s industrial era. Intrusion effects are still observed locally on the island today, but additional groundwater recharge by waste water has caused freshening elsewhere. We hypothesize that the observed aquifer replenishment locally enhances submarine groundwater discharge, flushing accumulated nutrients and pollutants towards Curaçao’s fringing coral reefs. We expect that this study’s insights motivate more hydrogeologists to use historical reports and data in future studies.

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]

A composite radial filter was developed and evaluated for filtration of NO3-N, P, and K2O from paddy field runoff for recharging aquifers. For zeolite (Z), granular activated charcoal (C), coarse sand (CS), and gravel (G) filter medias were placed in the annular concentric rings of the developed filter in various combinations of different thickness, viz. 1:2:4:4, 1:3:4:4, 1:2:2:4, 1:3:2:4 and 0:2:1:2 individually for five treatments, viz. T1, T2, T3, T4, and T5, respectively. At the radial filter output, a chlorination unit was used to inject sodium hypochlorite solution, commonly known in a dilute solution as bleach solution at a rate of 0.1 ml per unit discharge (lps) in order to purge bacterial contamination from the filtered water. Analysing water samples for four different inflow/outflow rates−0.42, 0.82, 1.24, and 1.66 lps before and after filtration allowed investigators to assess the efficacy of the composite radial filter. At all flow rates, the filtered water's NO3-N, P, and K2O values were determined to be within allowable limits. Based on removal efficiency of NO3-N, P, and K2O and reduced cost, the T5 treatment, which consists of filter materials C, CS, and G with thicknesses of 20, 10, and 20 cm (2:1:2), respectively, was found to be superior to the other four treatments (T1, T2, T3, and T4). After five hours of filter operation, the filter materials were cleaned and reused. Reused filter media were found to have NO3-N, P, and K2O values of 5.3, 5.8, and 10.9 ppm, respectively. These values were found to be slightly higher than those obtained from initially original filter materials for the same duration of operation. [ABSTRACT FROM AUTHOR]

Modeling groundwater is a significant paradigm in hydrology application, which supports human life and agricultural land in a wide range. Thus, groundwater modeling is more helpful in the hydrological system. Moreover, the crucial part of groundwater modeling is artificial recharging, which helps estimate groundwater levels. Also, the process of the recharge system differs based on ground conditions. Besides, spatial representations are explained in a graphical structure to estimate groundwater mapping. Henceforth, the drawn graphical representation illustrates the ground condition with its density. Furthermore, the MODFLOW model is mostly utilized to design the graphic structure. Also, this present review has collected areas of ground-level data including Varanasi, West Bengal, South Korea, Africa, Jordan, Italy, and Beauraing. So, several existing works are discussed related to the Varanasi district. Finally, several chief parameters are discussed in tabular and graphical formats. Also, systematic future works are recommended in conclusion section. Thus, this review supports the researchers in discovering past difficulties and better solutions for the future. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In arid and semi-arid countries like Iraq, which suffer from water scarcity due to the effects of climate change and decreased surface water flow, groundwater is considered a vital source of irrigation water. This study is concerned with the influence of artificial recharge on the rehabilitation of the unconfined aquifer called Al-Dibdibba, located between the cities of Najaf and Kerbala in central Iraq around 31°550' N and 32°450' N and 43°300' E and 44°300' E. Due to excessive groundwater pumping rates for irrigation, this aquifer has suffered from groundwater decline and increased salinization during the previous 20 years. By establishing a conceptual model in the groundwater modeling system software (GMS), a numerical model was made to simulate groundwater flow. Artificial recharge using recycled water (tertiary treatment) from Kerbala's primary WWTP was carried out using 25 injection wells. The model was calibrated against historical and observed water level data for periods from 2016 to 2017. Three scenarios to predict how the aquifer would act with artificial recharge of 5%, 8%, and 10% from the total daily outflow of the WWTP in Kerbala (100000 m3/day) were studied. The calibration model met the observed values of groundwater levels with R2 = 0.989 for steady-state simulations and R2 = 0.987 for transient simulations. In the final analysis of the simulation, the results show that the maximum predicted groundwater level was raised by the injection of treated water through 25 wells by 1.05 m for 5000 m3/day, 2 m for 8000 m3/day, and 3 m for 10,000 m3/day recharge pumping rates. In addition, if water were pumped into the aquifer, it might support the development of agricultural lands covering more than 93 km2. So, artificial recharge can be considered one of the important solutions to adaptation to the effects of climate change and desertification in Iraq. [ABSTRACT FROM AUTHOR]

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]

This paper aims at the optimal design of a system of small solid barrier-type stone dams in a semi-realistic study case, determining the number, location and height of dams and a borrow-pit (BP)'s location for benefit maximization and cost minimization of objectives: (a) maximum flood protection, (b) maximum underlying aquifers' artificial recharge, (c) minimum dams' construction cost and (d) minimum stonework transportation cost. The simplified conceptual model involves no hydraulic simulation; flow characteristics are not considered, while no dam is assumed to affect another dam's benefit/cost values. Hence, all partial benefit/cost values can be separately pre-calculated, for each one of the available dam locations for all available heights and BP locations, deriving from data concerning topography, geology/soil, land uses, construction and transportation costs. Any solution proposing a system of dams of various heights and a BP exhibits a total management value equal to the sum of the respective partial benefit/cost values of each dam. The multi-objective optimization problem is formulated into a single-objective minimization problem; the difference of costs minus benefits is to be minimized. Simple, elitist genetic algorithms (GAs) are used, coupled with sophisticated post-processing of results, able to produce optimized design solutions and strategies. HIGHLIGHTS Optimization of small dam system in mountainous stream basins.; Find optimal dams' locations and heights, and a borrow-pit's location.; Construction and stonework transport costs – flood protection and aquifer recharge benefits = minimum.; A simplified model allows the pre-calculation of benefits/costs and reduces computational load.; The ‘OptiDams’ tool serves as a decision-support tool in the design phase of relevant works.;

The purpose of this study is to quantitatively investigate the effects of artificial recharge of treated wastewater of Meybod and Ardakan cities with infiltrations and injection wells and comparing the economics of the two alternatives. In this study, the simulation of the groundwater flow in aquifer for a one-year period of 2002-2003 was carried out using the MODFLOW model and three locations were selected for artificial recharge. The annual volume of treated wastewater to recharge was estimated at 13.2 million cubic meters and the average level increase within a radius of three kilometers from the artificial feeding site was about 0.8 meters. The price of each cubic meter of water extracted from artificial feeding, excluding the costs of transfer and treatment of wastewater by the infiltration basin method in feeding places No. 1, 2 and 3, is equal to 342.2, 417.4 and 9.381 rials and with the injection well method it was obtained as 506.2, 515.2 and 495.7 rials, respectively. The cost of transporting each cubic meter of water to places 1, 2 and 3 (which are 13200, 11000 and 9000 meters from the treatment plant, respectively) was equal to 3580, 2958 and 2418 rials, respectively. Therefore, choosing the right place is one of the most important points in the design of such systems.

Introduction Water scarcity due to climate change and growing water demand in different consumption sectors is a major environmental crisis that drives arable lands to a state of degradation, especially in dry regions. Artificial recharge of groundwater (ARG) through floodwater spreading (FWS) which is a potential measure for reversing this emerging trend is investigated in this research. Floodwater harvesting has become an increasingly important technique to improve water security and caused a renewed interest in research and implementation. According to the diverse objectives and methods of implementing artificial recharge of groundwater (ARG) systems, various factors must be considered when choosing a method for quantifying recharge. Therefore, the rate of aquifer recharge is one of the most difficult items to measure in groundwater (GW) resources evaluation. In the soil water balance method (and in the Zero Flux Plane method), soil water movement is inferred by measuring the changes in water content of the soil profile by gravimetric sampling or automatic devices. These methods have not been proven satisfactory in low flow conditions, as there is often insufficient resolution to detect the movement of small quantities of water. Therefore, other methods, based on hydraulic conductivity, potential gradients, and directly calculated water fluxes for unsaturated flow were developed. The Buckingham-Darcy law can be used under the steady flow condition where water contents and fluxes change with depth but do not vary as a function of time. It has been employed in arid and semiarid conditions for recharge estimation. or for assessing the exchange flow between the surface water reservoir and GW. The method requires measurements or estimates of the vertical total head gradient and the unsaturated hydraulic conductivity at the ambient soil water content following the Buckingham-Darcy equation. The overall objective is to evaluate a floodwater spreading system that was installed in 1981 at the Gareh Bygone Plain, southern Iran for recharging the groundwater table. Materials and Methods To assess the artificial recharge of groundwater through turbid floodwater spreading, three wells, ~30 m deep, were dug in a 37-year-old recharge basin in planted Acacia forest, bare soil, and pasture land uses, respectively. Soil hydraulic parameters of the vadose zone layers (30 m thickness) were measured in the field and laboratory. One well was equipped with pre-calibrated TDR sensors throughout the well profile for measuring the changes in soil water content along the vadose zone. The volumetric soil-water content was measured continuously from Sep. 2010 to Sep. 2020 with closer temporal increments after floodwater spreading events. Rainfall, ponding water depth, and duration were also measured. Recharge through the vadose zone was assessed by the soil-water balance (SWB) method, as measured in the field as well as by calibrating the Hydrus-1D (H1D) model through the inverse solution. Results and discussion Results showed that the wetting front was interrupted at a layer with fine soil accumulation over a coarse-textured gravely layer at a depth of ~4 m. The large differences in hydraulic conductivity of the two successive layers seemed to cause the transformation of the wetting front water movement into fingering flow. The changes in downward water flux complicated TDR measurement after the depth of 4 m. However, noticeable but temporary changes in the soil water content were detected in some of the layers below the 4 m was evidence for fingering flow after the flood events. Validation of the simulated flow by the H1D model vs. the one observed by SWB (with RMSE 3.45; R2 0.994) showed that the model performed well in flux estimation. The recharge ratio was calculated for the 2010 to 2020 events as 26 to 84 average of 55 % for all events and 63 to 84 average of 75 % for large impounded floodwater in the basin, respectively. Conclusion Although a reliable set of data is obtained for calculating recharge at the very location of this study, up-scaling of the results for the entire floodwater systems and for the other flooding events with extreme volume and flow rate needs an extended investigation period and thorough identification of the underlying layers. The determined hydraulic properties of the RLs obtained in this study will be utilized in future research works in the FWS systems in our study site. The contributions of this thesis can be summarized as a) development of approaches for application, calibration, and validation of existing models with limited available data, b) the incorporation of new concepts into the models used, c) generating a unique and robust field data set to support the modeling approaches and d) provision of new information in the context of floodwater harvesting and its impact on groundwater recharge. Floodwater harvesting, especially in the form of FWS, is an emerging issue in water management in dry regions, which needs a better understanding and evaluation of its impact on the surrounding environment. Small-scale but nature-friendly water management plans, such as FWS systems, are seriously criticized since there are numerous methods, which are more attractive in terms of investments and money return to investors. However, they are rarely investigated. This study provided quantitative evidence that proves the effectiveness of FWS systems.

The goal of the present research is to figure out how to increase the efficiency with which water resources are used in mountainous relief regions on the example of the Ararat Artesian Basin of the Republic of Armenia. The accumulation of significant water runoffs in reservoirs under difficult hydrogeological conditions requires not only large investments in construction, but also in the transportation of water to the consumer, which is fraught with significant water infiltration losses. The paper shows that by the example of artificial recharge of the Ararat Artesian Basin, instead of building a new reservoir to collect 40 million m3 of water per year, which requires huge capital investments (5.75-6.25 USD/m3), the financial costs can be significantly reduced (0.05-0.075 USD/m3) by pumping the same volume of water into the groundwater basin. The obtained results can be used both in different regions of Armenia and in countries with mountainous relief.

Soil aquifer treatment (SAT) is a managed aquifer recharge technology that involves the utilization of treated wastewater as a source. Widely implemented in countries like Australia, Israel, and Spain, SAT offers technical (flexibility), economic (lower investment cost), and environmental (lower energy consumption) advantages that invite people in other countries to assess its potential. There have been numerous research studies and experiments conducted on the process level of SAT, focusing on how to eliminate pollutants and improve water quality. However, research at the system level is limited, which hampers its widespread application, especially in developing countries. In this paper, I provide a comprehensive guideline that highlights important factors to consider when implementing SAT as a technology. Proper site selection and careful planning steps, including pretreatment, hydrogeological factors, and economic calculations, can significantly improve the performance of an SAT system. The regulatory component acts as a barrier to the expansion of SAT facilities worldwide due to the lack of harmonization in regulations. This study includes the details and results of an examination of the legal framework and establishes comparative guidelines and water quality parameters that must be met by SAT projects utilizing reclaimed water. The maintenance and monitoring of the SAT system are also essential to anticipating and addressing potential issues such as clogging. Lastly, the social aspect, which is of utmost importance, should be carefully considered. It is advisable to ensure transparent communication with end users from the early stages of the project. These key elements are interconnected, and none should be considered less significant than the others. [ABSTRACT FROM AUTHOR]

Water plays a vital role in all living organisms on earth. With rapid urbanization, water is exploited at a greater pace than any other natural resource. The unavailability of water for all basic needs is at great risk. An optimization approach was developed to identify optimal sub-catchment with maximum runoff to implement Artificial Ground Recharge Points (AGRP) to raise the water groundwater table to mitigate the above-stated problem. This research focuses on developing an AGRP in the Noyyal River basin sub-catchments in Coimbatore city of Tamil Nadu, India. The methodology consists of three phases; in the first phase, the data for the work are collected from various sources. In the next phase, the data are pre-processed to convert various data formats to a standard format for easy processing. In the third phase, the pre-processed data are passed as an input to the genetic algorithm, the fuzzy logic is used as a fitness function to effectively calculate the rainfall-runoff events of each sub-catchments. The rules for calculating rainfall-runoff are carried out at three levels, as the first level, the area of influence in each sub-catchment by each rain gauge station is calculated to assign the rainfall values. In the second level, the area of influence and Land Use/Land Cover (LULC) classification for each sub-catchment is carried out to assign runoff co-efficient for each classification. As the final level, area of influence, LULC, and soil classification for each sub-catchment were carried out to calculate the infiltration rate. The classified data are passed as an input to calculate the rainfall-runoff for each sub-catchments for a period of eleven years (2010–2020) is done. The optimal sub-catchments with maximum runoff are obtained. The assessment of rainfall-runoff events for various sub-catchments in the study region indicates water flow in the streams. The long flow of streams into the city results in fresh rainwater being contaminated, contributing to groundwater contamination. The GA-FUZZY provides optimal sub-catchments to establish AGRP to use rainfall water effectively. The outcome of the work is a scalable methodology that can help the Public Works Department to implement AGRP in various river basins to increase the water table. [ABSTRACT FROM AUTHOR]

The goal of the present research is to figure out how to increase the efficiency with which water resources are used in mountainous relief regions on the example of the Ararat Artesian Basin of the Republic of Armenia. The accumulation of significant water runoffs in reservoirs under difficult hydrogeological conditions requires not only large investments in construction, but also in the transportation of water to the consumer, which is fraught with significant water infiltration losses. The paper shows that by the example of artificial recharge of the Ararat Artesian Basin, instead of building a new reservoir to collect 40 million m³ of water per year, which requires huge capital investments (5.75-6.25 USD/m³), the financial costs can be significantly reduced (0.05-0.075 USD/m³) by pumping the same volume of water into the groundwater basin. The obtained results can be used both in different regions of Armenia and in countries with mountainous relief. [ABSTRACT FROM AUTHOR]

Accurate groundwater management requires the estimation and propagation of rainfall-surface runoff. Rainfall is the principal source of groundwater recharge. Consequently, it is essential to monitor precipitation and runoff to assess water availability. Developing hydrometeorological data is necessary to design water resources and artificial recharge in Tamellalt. This study has two objectives: first, to estimate this region's runoff storm water using the storm water management model (SWMM) with the soil conservation service curve number (SCS-CN) method and second, to use the Iber code to create runoff flow maps based on runoff depth using the 2D shallow Saint–Venant's water model for finite volume. It shows that the rainfall is instantly infiltrated. Iber simulation runoff is due only to the exterior zones. This is confirmed by surface lithology. Terrain permeability is characterized by mean or high capacity. The extreme northern east zone shows a water depth exceeding 11 m. The eastern zone exceeds 15 m of water depth. The western submergence region has an approximate 3-m depression and 0.8-m water depth. Finally, the western subsurface zone of the south is characterized by a 1.8-m depression and a 0.4-m water depth. The extreme northern east and eastern zones can be considered favorite artificial recharge zones because of their high permeability and greatest water depth, considered natural water storage on the plain surface. [ABSTRACT FROM AUTHOR]

A hydro-economic approach for planning on-farm managed aquifer recharge is developed and demonstrated for two contiguous sub-basins in California’s Central Valley, USA. The amount and timing of water potentially available for recharge is based on a reoperation study for a nearby surface-water reservoir. Privately owned cropland is intermittently used for recharge with payments to landowners that compensate for perceived risks to crop health and productivity. Using all cropland in the study area would have recharged approximately 4.8 km3 (3,900 thousand acre-feet) over the 20-year analysis period. Limits to recharge effectiveness are expected from (1) temporal variability in recharge water availability, (2) variations in infiltration rate and few high-infiltration recharge sites in the study area, and (3) recharged water escaping from the study area groundwater system to surface water and adjacent sub-basins. Depending on crop tolerance to ponding depth, these limitations might be reduced by (1) raising berm heights on higher-infiltration-rate croplands and (2) creating dedicated recharge facilities over high-infiltration-rate sites.

Artificial recharge (AR) is the process whereby surface water is directed purposely underground to augment natural replenishment of groundwater reserves. During the period 1996–1998, the Research Institute for Groundwater started artificial recharge using infiltration basins in El Bustan experimental station in the western Nile Delta region. Recently, during the period 2020–2021, artificial recharge activities have been resumed in the experimental station. In this work, changes in hydrological conditions affecting the experimental station since its inception are reviewed and assessed. Artificial recharge using the infiltration basin are then applied, where results of these experiments are evaluated and compared to the previous ones. This is achieved with the objective of making an updated evaluation of the prospects of artificial recharge considering the changes in hydrological conditions. The study revealed that rise of groundwater levels is the major change affecting aquifer conditions in the study area. Such progressive rise of groundwater levels resulted in reducing the vadose zone thickness by more than 50% of its original thickness in 1996. This rise is attributed to uncontrolled recharge due seepage from nearby canals and irrigation return flow in the western Nile Delta region for the past 25 years. In view of the impacts of uncontrolled recharge, it is concluded that future work should shift from AR to managed aquifer recharge (MAR) to store water in the aquifer for subsequent recovery. It is recommended that further studies should use numerical modeling for exploring MAR schemes that can sustain the aquifer hydrologic equilibrium. Such MAR schemes should facilitate conjunctive use of surface and groundwater for improved water use management in the western Nile Delta region.

Well clogging was studied at an aquifer storage transfer and recovery (ASTR) site used to secure freshwater supply for a flower bulb farm. Tile drainage water (TDW) was collected from a 10-ha parcel, stored in a sandy brackish coastal aquifer via well injection in wet periods, and reused during dry periods. This ASTR application has been susceptible to clogging, as the TDW composition largely exceeded most clogging mitigation guidelines. TDW pretreatment by sand filtration did not cause substantial clogging at a smaller ASR site (2 ha) at the same farm. In the current (10 ha) system, sand filtration was substituted by 40-μm disc filters to lower costs (by 10,000–30,000 Euro) and reduce space (by 50–100 m2). This measure treated TDW insufficiently and injection wells rapidly clogged. Chemical, biological, and physical clogging occurred, as observed from elemental, organic carbon, 16S rRNA, and grain-size distribution analyses of the clogging material. Physical clogging by particles was the main cause, based on the strong relation between injected turbidity load and normalized well injectivity. Periodical backflushing of injection wells improved operation, although the disc filters clogged when the turbidity increased (up to 165 NTU) during a severe rainfall event (44 mm in 3 days). Automated periodical backflushing, together with regulating the maximum turbidity (<20 NTU) of the TDW, protected ASTR operation, but reduced the injected TDW volume by ~20–25%. The studied clogging-prevention measures collectively are only viable as an alternative for sand filtration when the injected volume remains sufficient to secure the farmer's needs for irrigation. [ABSTRACT FROM AUTHOR]