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

The fate of selected UV filters (UVFs) was investigated in two soil aquifer treatment (SAT) systems, one supplemented with a reactive barrier containing clay and vegetable compost and the other as a traditional SAT reference system. We monitored benzophenone-3 (BP-3) and its transformation products (TPs), including benzophenone-1 (BP-1), 4,4′-dihydroxybenzophenone (4DHB), 4-hydroxybenzophenone (4HB), and 2,2′-dihydroxy-4-methoxybenzophenone (DHMB), along with benzophenone-4 (BP-4) and avobenzone (AVO) in all involved compartments (water, aquifer sediments, and biofilm). The reactive barrier, which enhances biochemical activity and biofilm development, improved the removal of all detected UVFs in water samples. Among monitored UVFs, only 4HB, BP-4, and AVO were detected in sediment and biofilm samples. But the overall retained amounts were several orders of magnitude larger than those dissolved. These amounts were quantitatively reproduced with a specifically developed simple analytical model that consists of a mobile compartment and an immobile compartment. Retention and degradation are restricted to the immobile water compartment, where biofilm absorption was simulated with well-known compound-specific Kow values. The fact that the model reproduced observations, including metabolites detected in the biofilm but not in the (mobile) water samples, supports its validity. The results imply that accumulation ensures significant biodegradation even if the degradation rates are very low and suggest that our experimental findings for UVFs and TPs can be extended to other hydrophobic compounds. Biofilms act as accumulators and biodegraders of hydrophobic compounds.

Managed aquifer recharge (MAR) is an emerging solution to effectively replenish overused groundwater resources, but high associated costs often hinder its uptake. There are several parameters to consider when determining the cost of MAR, including recharge types, MAR schemes scale, land acquisition, operation and maintenance period, and the hydrogeological setting. Hydraulic conductivity and its spatial variability are the most significant hydrogeological parameters for predicting infiltration rates at MAR sites, but limited data availability makes accurate predictions often challenging. Hence, it is essential to increase data availability to optimize MAR efficiency and to better assess its economic performance. Therefore, a novel approach for MAR planning is presented in this article to efficiently enhance the data availability during the conceptual stage of MAR planning by combining site exploration, spatially resolved infiltration rate estimation, and cost analysis. The approach was applied at an actual MAR site in Vincenza, Italy, and incorporated an electromagnetic induction survey and direct push profiling as across-scale investigation methods to enhance site delineation and subsequent parameterization of the identified zones using laboratory analysis of collected samples. This MAR site is particularly suitable for its heterogeneous subsurface structure and potential to counteract groundwater depletion. The performed investigation resulted in an image of the lateral variation of subsurface conditions and allowed the delineation of three zones with different infiltration behavior, with 99.5% of infiltration occurring in just two zones, representing only 22.1% of the site. In this particular scenario, the overall cost per cubic meter of recharged water can be reduced by 59.1% by identifying and eliminating unfavorable zones. This study provides scientists and practitioners with a useful tool for MAR planning that can be applied to a wide range of sites with comp

The fate of selected UV filters (UVFs) was investigated in two soil aquifer treatment (SAT) systems, one supplemented with a reactive barrier containing clay and vegetable compost and the other as a traditional SAT reference system. We monitored benzophenone-3 (BP-3) and its transformation products (TPs), including benzophenone-1 (BP-1), 4,4'-dihydroxybenzophenone (4DHB), 4-hydroxybenzophenone (4HB), and 2,2'-dihydroxy-4-methoxybenzophenone (DHMB), along with benzophenone-4 (BP-4) and avobenzone (AVO) in all involved compartments (water, aquifer sediments, and biofilm). The reactive barrier, which enhances biochemical activity and biofilm development, improved the removal of all detected UVFs in water samples. Among monitored UVFs, only 4HB, BP-4, and AVO were detected in sediment and biofilm samples. But the overall retained amounts were several orders of magnitude larger than those dissolved. These amounts were quantitatively reproduced with a specifically developed simple analytical model that consists of a mobile compartment and an immobile compartment. Retention and degradation are restricted to the immobile water compartment, where biofilm absorption was simulated with well-known compound-specific Kow values. The fact that the model reproduced observations, including metabolites detected in the biofilm but not in the (mobile) water samples, supports its validity. The results imply that accumulation ensures significant biodegradation even if the degradation rates are very low and suggest that our experimental findings for UVFs and TPs can be extended to other hydrophobic compounds. Biofilms act as accumulators and biodegraders of hydrophobic compounds.

The regeneration of wastewater has been recognized as an effective strategy to counter water scarcity. Nonetheless, Wastewater Treatment Plant (WWTP) effluents still contain a wide range of contaminants of emerging concern (CECs) even after water depuration. Filtration through Soil Aquifer Treatment (SAT) systems has proven efficient for CECs removal although the attenuation of their associated biological effects still remains poorly understood. To evaluate this, three pilot SAT systems were monitored, two of them enhanced with different reactive barriers. SATs were fed with secondary effluents during two consecutive campaigns. Fifteen water samples were collected from the WWTP effluent, below the barriers and 15 m into the aquifer. The potential attenuation of effluent-associated biological effects by SATs was evaluated through toxicogenomic bioassays using zebrafish eleutheroembryos and human hepatic cells. Transcriptomic analyses revealed a wide range of toxic activities exerted by the WWTP effluents that were reduced by more than 70% by SAT. Similar results were observed when HepG2 hepatic cells were tested for cytotoxic and dioxin-like responses. Toxicity reduction appeared partially determined by the barrier composition and/or SAT managing and correlated with CECs removal. SAT appears as a promising approach to efficiently reduce effluent-associated toxicity contributing to environmental and human health preservation.

The fate of selected UV filters (UVFs) was investigated in two soil aquifer treatment (SAT) systems, one supplemented with a reactive barrier containing clay and vegetable compost and the other as a traditional SAT reference system. We monitored benzophenone-3 (BP-3) and its transformation products (TPs), including benzophenone-1 (BP-1), 4,4'-dihydroxybenzophenone (4DHB), 4-hydroxybenzophenone (4HB), and 2,2'-dihydroxy-4-methoxybenzophenone (DHMB), along with benzophenone-4 (BP-4) and avobenzone (AVO) in all involved compartments (water, aquifer sediments, and biofilm). The reactive barrier, which enhances biochemical activity and biofilm development, improved the removal of all detected UVFs in water samples. Among monitored UVFs, only 4HB, BP-4, and AVO were detected in sediment and biofilm samples. But the overall retained amounts were several orders of magnitude larger than those dissolved. These amounts were quantitatively reproduced with a specifically developed simple analytical model that consists of a mobile compartment and an immobile compartment. Retention and degradation are restricted to the immobile water compartment, where biofilm absorption was simulated with well-known compound-specific Kow values. The fact that the model reproduced observations, including metabolites detected in the biofilm but not in the (mobile) water samples, supports its validity. The results imply that accumulation ensures significant biodegradation even if the degradation rates are very low and suggest that our experimental findings for UVFs and TPs can be extended to other hydrophobic compounds. Biofilms act as accumulators and biodegraders of hydrophobic compounds., This work was financially supported by the Spanish government (project CONMIMO, TED2021-131188B-C32 and TED2021-131188B-C31), the Catalan Research Project RESTORA (ACA210/18/00040) and SGR (2021-SGR-00609), and by EU project MARADENTRO (PCI2019-103425 and PCI2019-103603). IDAEA-CSIC is a Center of Excellence Severo Ochoa (Grant CEX2018-000794-S funded by MCIN/AEI/10.13039/501100011033). The authors also thank the Consorci d’Aigües de la Costa Brava Girona (CACBG) for the access to the WWTP, and to BEKOlut for the provision of the QuEChERS used. Pedro Chamorro is acknowledged for his help in the UVFs analysis., Peer Reviewed, Postprint (published version)

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

This is a study the influence of soil carbon amendments, as part of linked laboratory experiments and field operations, for the cycling of nitrogen compounds during managed aquifer recharge (MAR). The MAR field site is in Watsonville, CA, and collects and infiltrates stormwater runoff on a working ranch. Various soil carbon amendments were applied as permeable reactive barriers (PRBs), including wood chips and almond shells, two carbon sources previously known to enhance microbially mediated denitrification. Intact soil cores were recovered from an infiltration basin and used in flow-through experiments to replicate and extend field observations to quantify substrate controls on biogeochemical processes. For laboratory experiments, PRBs included mixtures of carbon sources and native soil at specific ratios (wood chips 1:1; almond shells 1:1, 1:3, and 1:10). Almond shells mixed with soil as 50% and 25% by volume removed the most nitrate in the laboratory experiments. These two treatments also produced higher amounts of manganese and iron. Elevated levels of these trace metals are interpreted as an indication of a more reducing condition where denitrification can occur more favorably. Wood chips removed a modest amount of nitrate, but also produced nitrite, indicating incomplete denitrification. In field operations, wood chips removed more nitrate than almond shells but also produced more nitrite. Based on isotopic results, nitrite oxidation may be occurring in the wood chip treated areas. We conclude that, overall, almond shells, at a high enough amount, are a better soil amendment than wood chips for removing nitrate during infiltration for MAR.

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

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

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

Agricultural aquifer storage recovery and transfer (ASTR) stores excess fresh water for later reuse in irrigation. Moreover, water quality improves because chemical pollutants and pathogens will be removed by degradation and attachment to the aquifer material. The source water may contain the bacterial plant pathogen Ralstonia solanacearum which causes plant infections and high yield losses. We used quantitative microbial risk assessment (QMRA) to investigate the removal of R. solanacearum during ASTR to predict infection risks of potato plants after irrigation with the recovered water. Laboratory experiments analyzed the ASTR treatment by investigating the bacterial die-off in the water phase and the removal by attachment to the aquifer sediment. Die-off in the water phase depends on the residence time and ranged between 1.3 and 2.7 log10 after 10 or 60 days water storage, respectively. A subpopulation of the bacteria persisted for a prolonged time at low concentrations which may pose a risk if the water is recovered too early. However, the natural aquifer sand filtration proofed to be highly effective in removing R. solanacearum by attachment which depends on the distance between injection and abstraction well. The high removal by attachment alone (18 log10 after 1 m) would reduce bacterial concentrations to negligible numbers. Upscaling to longer soil passages is discussed in the paper. Infection risks of potato plants were calculated using a dose-response model and ASTR treatment resulted in negligible infection risks of a single plant, but also when simulating the irrigation of a 5 ha potato field. This is the first QMRA that analyzed an agricultural ASTR and the fate of a plant pathogen focusing on plant health. QMRA is a useful (water) management tool to evaluate the treatment steps of water reclamation technologies with the aim to provide safe irrigation water and reduce risks disseminating plant diseases.

Managed aquifer recharge (MAR) is increasingly used to secure drinking water supply worldwide. The city of Amsterdam (The Netherlands) depends largely on the MAR in coastal dunes for water supply. A new MAR scheme is proposed for the production of 10 × 106 m3/year, as required in the next decade. The designed MAR system consists of 10 infiltration ponds in an artificially created sandbank, and 25 recovery wells placed beneath the ponds in a productive aquifer. Several criteria were met for the design, such as a minimum residence time of 60 days and maximum drawdown of 5 cm. Steady-state and transient flow models were calibrated. The flow model computed the infiltration capacity of the ponds and drawdowns caused by the MAR. A hypothetical tracer transport model was used to compute the travel times from the ponds to the wells and recovery efficiency of the wells. The results demonstrated that 98% of the infiltrated water was captured by the recovery wells which accounted for 65.3% of the total abstraction. Other sources include recharge from precipitation (6.7%), leakages from surface water (13.1%), and natural groundwater reserve (14.9%). Sensitivity analysis indicated that the pond conductance and hydraulic conductivity of the sand aquifer in between the ponds and wells are important for the infiltration capacity. The temperature simulation showed that the recovered water in the wells has a stable temperature of 9.8–12.5 °C which is beneficial for post-treatment processes. The numerical modelling approach is useful and helps to gain insights for implementation of the MAR., Water Resources

Agricultural aquifer storage recovery and transfer (ASTR) stores excess fresh water for later reuse in irrigation. Moreover, water quality improves because chemical pollutants and pathogens will be removed by degradation and attachment to the aquifer material. The source water may contain the bacterial plant pathogen Ralstonia solanacearum which causes plant infections and high yield losses. We used quantitative microbial risk assessment (QMRA) to investigate the removal of R. solanacearum during ASTR to predict infection risks of potato plants after irrigation with the recovered water. Laboratory experiments analyzed the ASTR treatment by investigating the bacterial die-off in the water phase and the removal by attachment to the aquifer sediment. Die-off in the water phase depends on the residence time and ranged between 1.3 and 2.7 log10 after 10 or 60 days water storage, respectively. A subpopulation of the bacteria persisted for a prolonged time at low concentrations which may pose a risk if the water is recovered too early. However, the natural aquifer sand filtration proofed to be highly effective in removing R. solanacearum by attachment which depends on the distance between injection and abstraction well. The high removal by attachment alone (18 log10 after 1 m) would reduce bacterial concentrations to negligible numbers. Upscaling to longer soil passages is discussed in the paper. Infection risks of potato plants were calculated using a dose-response model and ASTR treatment resulted in negligible infection risks of a single plant, but also when simulating the irrigation of a 5 ha potato field. This is the first QMRA that analyzed an agricultural ASTR and the fate of a plant pathogen focusing on plant health. QMRA is a useful (water) management tool to evaluate the treatment steps of water reclamation technologies with the aim to provide safe irrigation water and reduce risks disseminating plant diseases., Sanitary Engineering

Managed aquifer recharge (MAR) techniques are in demand to cope with water scarcity challenges posed by climate change and groundwater overexploitation. One of the long-lasting technical issues associated with MAR systems is physical clogging. The intrusion and deposition of external fines during water recharge reduce the infiltration capacity of the site over time. Operation and maintenance (O&M) costs are experienced directly at the site to restore the original efficiency of infiltration rates. Thus, investors need reliable estimations of the risk of clogging during the planning of the site. As a rule, in MAR design, the main parameter of concern for physical clogging is the total suspended solids (TSS), and most clogging models rely on experiment calibrations in 1D sand columns. However, secondary processes can control the development and spatial distribution of physical clogging in field conditions. The proposed work aims to detect key clogging factors directly in the field and to model these processes for reproducibility at other sites. The fieldwork is conducted at the two-stage infiltration basin in Suvereto (Tuscany, Italy). Spatial factors are included in the analysis (i.e. basin topography) to explain clogging patterns in the field altered by erosion processes. The observed clogging profiles at two sampled locations exhibiting clogging are replicated by a mathematical model. Based on the computation of annual erosion rates in the pond and fines’ redistribution, the exceeding fines’ contents over depth are validated with an RMSE of 2.53% and 12.53%. The infiltration capacity of the site is estimated to reach a stable value of 90% of the initial infiltration capacity over 20 years, given the Suvereto basin features. The model's parameterisation from field measurements represents a great advantage over existing clogging models due to its transferability to other MAR sites. The assessment of the risk of clogging supported by field characterization and

In light of rapid population growth and climate-change pressures on water resources, there is an urgent need in many African cities to shift to more resilient, decentralised, nature-based approaches. In response, the City of Cape Town's Water Strategy document proposes various alternative water supply sources. One is Managed Aquifer Recharge (MAR) using the Cape Flats Aquifer (CFA). Overlying the CFA are a significant number of stormwater ponds that were originally designed solely to prevent flooding. These ponds could be retrofitted to infiltrate stormwater run-off, recharging the aquifer and serving a water treatment function using nature-based approaches. Many of these mono-functional ponds are in neighbourhoods that are socio-economically disadvantaged through former apartheid spatial planning. These ponds are frequently litter-filled, used for dumping rubble and, on occasion, occupied with informal housing. It is in this context that the conversion of engineered single-purpose stormwater ponds into multi-functional space is proposed using a demonstration site in Mitchells Plain, Cape Town. The ‘Pathways to water resilient South African cities (PaWS)’ project is a collaboration between the Future Water Institute at the University of Cape Town (UCT) and University of Copenhagen (UCPH), funded through DANIDA. This research is revealing how maximum benefit could be derived from these water management systems by adopting low-cost, easy to install blue-green interventions that rely on nature-based approaches. The findings from the research have relevance across Southern Africa where several large cities have existing stormwater ponds designed for flood control or as passive open green spaces. It offers valuable strategies for how these single-purpose ponds can be transformed into multifunctional blue-green spaces in ways that build resilience while addressing the environmental injustice that is a legacy of South Africa's ‘green apartheid’.

[EN] Managed aquifer recharge (MAR) and, in particular, recharge by direct injection into the aquifer through wells or boreholes allows for a series of very interesting solutions to solve various technical and environmental problems related to management of the urban water cycle. These problems include the overexploitation of water resources, marine intrusion or contamination of groundwater by irrigation returns. The island of Gran Canaria presents several of these problems; thus, the feasibility of implementing a recharge system has been studied to provide a solution to some of them, using a resource of great potential such as reclaimed water. A detailed characterization of groundwater quality in the study area was carried out, complemented by a field campaign with water sampling from the surrounding catchments, in situ analysis and subsequent laboratory analysis. Specifically, an MBR treatment with disinfection is proposed, where the final conclusions indicate that this is a technically and economically viable project, innovative in its application on islands, a priori with an acceptable productive recharge capacity, possibly scalable after the experimental phase and extrapolable to other locations with similar conditions. In addition, it presents a set of important environmental benefits with respect to conservation of and improvement of the state of the groundwater bodies in the studied area, as well contributing to knowledge of and research into water management in volcanic lands and islands.

Irrigation with surface water carrying plant pathogens poses a risk for agriculture. Managed aquifer recharge enhances fresh water availability while simultaneously it may reduce the risk of plant diseases by removal of pathogens during aquifer passage. We compared the transport of three plant pathogenic bacteria with Escherichia coli WR1 as reference strain in saturated laboratory column experiments filled with quartz sand, or sandy aquifer sediments. E. coli showed the highest removal, followed by Pectobacterium carotovorum, Dickeya solani and Ralstonia solanacearum. Bacterial and non-reactive tracer breakthrough curves were fitted with Hydrus-1D and compared with colloid filtration theory (CFT). Bacterial attachment to fine and medium aquifer sand under anoxic conditions was highest with attachment rates of max. katt1 = 765 day-1 and 355 day-1, respectively. Attachment was the least to quartz sand under oxic conditions (katt1 = 61 day-1). In CFT, sticking efficiencies were higher in aquifer than in quartz sand but there was no differentiation between fine and medium aquifer sand. Overall removal ranged between < 6.8 log10 m−1 in quartz and up to 40 log10 m−1 in fine aquifer sand. Oxygenation of the anoxic aquifer sediments for two weeks with oxic influent water decreased the removal. The results highlight the potential of natural sand filtration to sufficiently remove plant pathogenic bacteria during aquifer storage.

The Hampton Roads Sanitation District is heading a Managed Aquifer Recharge project designed to build water resiliency for the district as well as meet recent regulations concerning effluent released into the Chesapeake Bay. The Sustainable Water Initiative for Tomorrow (SWIFT) project will include five injection well fields across the Virginian Coast. The first of these fields to be implemented is the James River site, scheduled to begin in 2025. A model of the Virginia Coastal Plain region was created in 2009 and has been used to simulate the combined impact of the full-scale SWIFT project. This study estimated the change in hydraulic head in the Potomac Aquifer System caused by the proposed James River recharge well field at a regional and local level. That estimation required the use of a widely accepted model of the Virginia Coastal Plain developed in 2009 which was subjected to a limited validation using USGS monitoring well data for comparison. That model was then used to establish boundary conditions for a local scale model surrounding the James River site, after which each model was used to run four pumping scenarios with varying rates of recharge. The validation of the Virginia Coastal Plain model found it to be satisfactory for the scope of this work, and it was therefore used to interpolate boundary conditions for the developed local model. The regional and local model both showed an increase in the simulated head values of the Potomac Aquifer System. The regional model simulated a sharper initial increase than the local model, however, long term the local model simulated a greater impact to the groundwater levels from the proposed recharge.

A field injection experiment was performed in an anoxic sandy aquifer over 6 days to assess sorption characteristics of 7 commonly applied pesticides in agriculture and 2 frequently detected metabolites. Pesticide use changed considerably in the last decades, and there is insufficient knowledge of the fate of currently used pesticides in aquifers. Injected water arrival was monitored at 6 depth intervals of 1 m ranging from 11.4 to 32.2 m-below surface level with varying organic carbon contents (0.057–0.91%d.w.) to examine intra-aquifer variations in sorption. Observed pesticide concentrations were fit using a non-linear least squares routine to an advection-dispersion equation, from which retardation factors (R) were obtained. Pesticide degradation did not significantly influence the simulated R during the experiment. We observed that bentazon and cycloxydim were most mobile with R < 1.1 at all depths. Desphenyl chloridazon, methyl desphenyl chloridazon, and imidacloprid were, on average, less mobile, with maximum R of 1.5. Boscalid, chloridazon, fluopyram, and flutolanil showed a larger range of R, and R > 2.0 were observed in the shallowest part of the aquifer. Largest R were observed at the top of the aquifer and decreased with depth. Koc values varied similarly, which indicates that sorption is not only influenced by sedimentary organic matter (SOM) content but also by its sorption reactivity. Obtained sorption parameters were substantially lower than reported in a widely used pesticide sorption database, which suggests that sorption parameters are influenced by methodological differences and variations in the sorption reactivity of SOM. The large intra-aquifer variations in pesticide sorption highlights that aquifer heterogeneity should be considered in groundwater risk assessments., Sanitary Engineering, Geo-engineering

Irrigation with surface water carrying plant pathogens poses a risk for agriculture. Managed aquifer recharge enhances fresh water availability while simultaneously it may reduce the risk of plant diseases by removal of pathogens during aquifer passage. We compared the transport of three plant pathogenic bacteria with Escherichia coli WR1 as reference strain in saturated laboratory column experiments filled with quartz sand, or sandy aquifer sediments. E. coli showed the highest removal, followed by Pectobacterium carotovorum, Dickeya solani and Ralstonia solanacearum. Bacterial and non-reactive tracer breakthrough curves were fitted with Hydrus-1D and compared with colloid filtration theory (CFT). Bacterial attachment to fine and medium aquifer sand under anoxic conditions was highest with attachment rates of max. k att1 = 765 day -1 and 355 day -1, respectively. Attachment was the least to quartz sand under oxic conditions (k att1 = 61 day -1). In CFT, sticking efficiencies were higher in aquifer than in quartz sand but there was no differentiation between fine and medium aquifer sand. Overall removal ranged between < 6.8 log 10 m −1 in quartz and up to 40 log 10 m −1 in fine aquifer sand. Oxygenation of the anoxic aquifer sediments for two weeks with oxic influent water decreased the removal. The results highlight the potential of natural sand filtration to sufficiently remove plant pathogenic bacteria during aquifer storage., Sanitary Engineering

Groundwater dependent mega-cities exert enormous pressure on the watersheds in which they are situated, creating a demand for complex hydrogeologic modeling and analysis that provides decision-makers with the information they need. However, uncertainties about the characterization of the subsurface, hydrologic fluxes, and other model input, along with assumptions made during the modeling process can create difficulties in developing the models and interpreting the results in a way that ensures sustainable and equitable regional aquifer management. This dissertation uses a multiobjective analysis approach to determine the performance of spatially distributed aquifer management alternatives for the case study of the Valley of Mexico, where the Mexico City Metropolitan Area is situated. First, a three-dimensional finite-difference groundwater model is developed alongside an initial set of managed aquifer recharge alternatives and planning objectives in Chapter 2. The management alternatives tested show spatially distinct reductions in drawdown over the historical period for equivalent changes in storage and that combining multiple alternatives results in a more than an additive risk of groundwater flooding. These results point to the importance of including planning objectives calculated over diverse spatial extents in capturing impacts to groundwater security in urban basins. To address the potential for endogenous uncertainties in models to influence decision-making, Chapter 3 carries out a global sensitivity analysis across model parameter values and subsets of well observations using the model and alternatives developed in Chapter 2. Error metrics generally used to calibrate groundwater models are found to be sensitive to distinct parameters from those to which management objectives are sensitive and the coupled effects of the endogenous uncertainties have amplifying effects on the ranking of management alternatives. Both of these findings highlight the importance

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

Managed aquifer recharge (MAR) is an increasingly popular strategy for maintaining a sustainable water supply. Reclaimed water (sometimes referred to as recycled water) can be used as a supply of recharge water, providing environmental benefits, while natural processes improve the quality of this water. Planning and implementing such projects requires understanding of the flow patterns and geochemistry of the target aquifers in addition to health and logistical constraints. This dissertation contains three studies of conditions for various phases of reclaimed water MAR projects in two different hydrogeologic and legal settings. Chapter 2 is a suitability analysis of land for reclaimed water MAR in the California's Central Valley in the context of the Sustainable Groundwater Management Act, which requires Groundwater Sustainability Agencies (GSA) to develop Groundwater Sustainability Plans (GSP). Land is scored in terms of the suitability of its soil and proximity to potential sources of reclaimed water. Inherently unsuitable land is excluded based on land cover and mandatory buffers for domestic wells. Backwards particle tracking is used to identify areas where recharged water would not meet minimum residence time criteria specified in California's water code, and these areas are also excluded. Land deemed suitable for reclaimed water MAR is compared to the land needed by GSAs in critically overdrafted basins to fulfil the recharge goals laid out in their GSPs. Potential recycled water availability is determined based on the discharge volumes of local water recycling and wastewater treatment plants. Under existing conditions, only 2 out of 29 GSAs have enough potentially suitable land to meet their recharge goals using sufficiently high-quality reclaimed water as a source, and none have enough high quality water, though the numbers increase if existing treatment plants can be upgraded. Chapter 3 details a tracer study and monitoring project conducted at the LOTT Cle

Thesis Statement: Managed aquifer recharge (MAR) is a set of tools and protocols that purposefully collects water to replenish underground aquifers. Types of MAR vary in their capacity to recharge, the price to implement them, and the water quality of infiltrating water. Distributed stormwater collection MAR uses hillslopes and gravity to direct stormwater into collection basins where it then infiltrates back down into the aquifer. This dissertation uses techniques from microbiology, water analysis, carbon characterization, and metagenomic sequences to elucidate how the design of a distributed stormwater collection MAR basin impacts the microbial community, thus impacting the geochemical cycling and water quality. The addition of a carbon-rich permeable reactive barrier (PRB) layered on top of a collection basin promotes the removal of nitrates from agricultural stormwater. The removal of nitrates, along with most of the geochemical cycling in the subsurface soil, is primarily done by the native microbial community. However, prior to this research, it was unclear how the microbial was being impacted by either infiltration or infiltration with a carbon-rich PRB. There was also little research into how different PRB materials could have different results in both water quality and microbial community composition. This research’s overarching hypothesis was that the addition of a carbon-rich PRB would provide carbon to the native subsurface microbes and power their denitrification. We also hypothesized this carbon shift would provide a trophic benefit to a common consort of microbes and the type of carbon being provided would have different outcomes. This research gives first insights into the soil-microbe-water interactions that occur during MAR and helps provide a framework for a predictive understanding of the carbon and nutrient cycling occurring during MAR infiltration. We first looked at how the soil and water characteristics influence the microbial communities of

Intensive use of groundwater in the last century, as well as persistent and severe droughts, have diminished California’s groundwater resources to alarming levels over the last decade. Rising in prevalence as a way of both maintaining and improving groundwater levels is agricultural-managed aquifer recharge (ag-MAR), a technique that involves actively spreading water on the ground to encourage deep percolation to underlying aquifers. In the coming years, ag-MAR may be seen as a powerful tool in sustainable groundwater management. However, ag-MAR is not only a tool to replenish our groundwater resources, as the technique also provides multiple benefits to the environment, including nearby communities and wildlife. Flooded agricultural fields can provide temporary wetland habitats while recharging water to underlying aquifers. The goal for this study was to develop groundwater models using MODFLOW to quantitatively and qualitatively assess the benefits of ag-MAR for a groundwater basin in northern California in addition to being a wetland habitat for migratory birds. Through the development of a regional parent model and a more refined child model, we simulated the effects of ag-MAR and tested scenarios of increasing recharge rates and recharge duration. From the results of the model scenarios, we determined that increasing recharge rates, either by flooding more fields in a project area or prolonging the flooding periods, will yield a significant – and positive – hydrologic effect on groundwater levels and storage. With the analysis of the groundwater models’ results, it is possible to understand the hydrologic and environmental impacts of multi-benefit recharge projects, and how it can be scaled up spatially and temporally to increase the benefits to migratory birds and our groundwater resources for future projects across California.

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

Managed aquifer recharge (MAR) refers to a suite of methods by which excess surface water or non-conventional water is stored underground for subsequent recovery or environmental purposes. MAR solutions have been largely used in unconsolidated aquifers, while their application in karst aquifers is rare. This research presents the first results of a MAR viability study on the island of Vis, a small karstic island in the Adriatic Sea. Favorable geological and hydrogeological conditions enable the formation of karst aquifers, making the island autonomous in terms of water supply. The island’s main aquifer, exploited in the Korita well field, is protected from seawater intrusion by several hydrogeological barriers. However, climate change and high seasonal pressures related to tourism pose a threat to the future availability of freshwater. Multidisciplinary field and laboratory investigations were carried out to detail the geological and hydrogeological setting of the island and its groundwater resource. Field analyses consisted of groundwater monitoring and sampling, geophysical investigations (i.e., electrical resistivity tomography), and structural measurements. Laboratory analyses included measurements of principal cations and anions and tritium activity. Despite low precipitation during the observation period (September 2019-December 2020), the groundwater resource at the Korita site showed stable trends of physico-chemical parameters with a good storage potential and a long-term reserve. Geophysical investigations evidenced a relatively homogeneous sequence of the rock mass at a larger scale, while structural analyses indicated the occurrence of E-W karstified and open fractures that could represent a preferential flow path in the carbonate aquifer. A MAR solution for the Vis island was proposed combining an infiltration pond scheme with the direct injection of the accumulated waters into the aquifer using available wells. The potential water source could be repre

Intensive groundwater exploitation has depleted groundwater storage and led to a series of geo-environmental problems in Beijing Plain, China. Managed Aquifer Recharge (MAR) has been endorsed to mitigate the groundwater storage depletion and achieve groundwater sustainability. A pilot MAR has been tested in the Chaobai River catchment since 2015. An innovative large-scale MAR consisting of 9 cascade terraced infiltration ponds was proposed and its effectiveness was assessed in this study using an integrated modelling approach. The integrated model coupled the regional and local transient flow and transport processes. The transient regional flow model simulated historical groundwater level declines and storage depletion in the Beijing Plain from 1995 to 2018. The coupled regional and local flow model was used to simulate the pilot MAR test in the Chaobai River from 2015 to 2018. A significant groundwater level increase was observed nearby the pilot MAR since 2015. The transport model results indicate that approximately 40% of the infiltrated water was captured by pumping wells in the No.8 well field. The models were further used to assess the long-term effects of the large-scale MAR from 2020 to 2050. The simulation results show that the groundwater system will reach a new equilibrium state under the implementation of the large-scale MAR scheme. Almost 91% of the abstracted water in the No. 8 well field will come from the MAR infiltration. The proposed large-scale MAR is very effective in restoring the depleted aquifer storage and maintaining the groundwater abstraction in the No.8 well field. However, with the increase of the groundwater level, the infiltration rate of several ponds will decrease. Therefore, it is important to maintain a dynamic balance between artificial recharge and groundwater abstraction in order to achieve a sustainable long-term MAR operation in the region., Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Water Resources

Irrigation with surface water carrying plant pathogens poses a risk for agriculture. Managed aquifer recharge enhances fresh water availability while simultaneously it may reduce the risk of plant diseases by removal of pathogens during aquifer passage. We compared the transport of three plant pathogenic bacteria with Escherichia coli WR1 as reference strain in saturated laboratory column experiments filled with quartz sand, or sandy aquifer sediments. E. coli showed the highest removal, followed by Pectobacterium carotovorum, Dickeya solani and Ralstonia solanacearum. Bacterial and non-reactive tracer breakthrough curves were fitted with Hydrus-1D and compared with colloid filtration theory (CFT). Bacterial attachment to fine and medium aquifer sand under anoxic conditions was highest with attachment rates of max. katt1 = 765 day-1 and 355 day-1, respectively. Attachment was the least to quartz sand under oxic conditions (katt1 = 61 day-1). In CFT, sticking efficiencies were higher in aquifer than in quartz sand but there was no differentiation between fine and medium aquifer sand. Overall removal ranged between < 6.8 log10 m− 1 in quartz and up to 40 log10 m− 1 in fine aquifer sand. Oxygenation of the anoxic aquifer sediments for two weeks with oxic influent water decreased the removal. The results highlight the potential of natural sand filtration to sufficiently remove plant pathogenic bacteria during aquifer storage.

Study region: The study region is the Kamadhiya catchment (1150 km2), located in the Saurashtra region of the western state of Gujarat, India. The region has seen intensive development of check dams (CDs) for groundwater recharge with an estimated 27,000 CDs constructed up until 2018. Study focus: The impact of CDs on groundwater storage, food production and resilience are assessed for Kamadhiya catchment by estimating and comparing changes, across periods of low and high CD development, in potential recharge from CDs, rainfall trends, and irrigation demand. The analysis is carried out for the period from 1983 to 2015. New hydrological insights for the region: Groundwater storage gains observed following CD development can partly be attributed to an increase in high rainfall years after several drought years. Groundwater demand for irrigation has increased substantially, outweighing increase in groundwater recharge from CDs. This deficit in supply relative to demand is greatest in dry years, and when considered together with the low inter-annual carry-over storage of the region's hardrock aquifers, means that CDs capacity to enhance groundwater storage and mitigate the negative impacts of drought remains limited. Findings suggest that a standalone focus on MAR, unless complemented by greater emphasis on management of water demand and groundwater resources more broadly, may not be sufficient to achieve the long-term goals of sustainable groundwater and concurrently expanding agricultural crop production., Water Resources

An aquifer storage transfer and recovery (ASTR) system was studied in which tile drainage water (TDW) was injected with relatively high NO3 (about 14 mg/L) concentrations originating from fertilizers. Here we present the evolution of denitrification kinetics at 6 different depths in the aquifer before, and during ASTR operation. First-order denitrification rate constants increased over time before and during the first days of ASTR operation, likely due to microbial adaptation of the native bacterial community and/or bioaugmentation of the aquifer by denitrifying bacteria present in injected TDW. Push-pull tests were performed in the native aquifer before ASTR operation. Obtained first-order denitrification rate constants were negligible (0.00–0.03 d−1) at the start, but increased to 0.17–0.83 d−1 after a lag-phase of about 6 days. During the first days of ASTR operation in autumn 2019, the arrival of injected TDW was studied at 2.5 m distance from the injection well. First-order denitrification rate constants increased again over time (maximum >1 d−1). Three storage periods without injection were monitored in winter 2019, fall 2020, and spring 2021 during ASTR operation. First-order rate constants ranged between 0.12 and 0.61 d−1. Denitrification coupled to pyrite oxidation occurred at all depths, but other oxidation processes were indicated as well. NO3 concentration trends resembled Monod kinetics but were fitted also to a first-order decay rate model to facilitate comparison. Rate constants during the storage periods were substantially lower than during injection, probably due to a reduction in the exchange rate between aquifer solid phases and injected water during the stagnant conditions. Denitrification rate constants deviated maximally a factor 5 over time and depth for all in-situ measurement approaches after the lag-phase. The combination of these in-situ approaches enabled to obtain mo, Sanitary Engineering, Geo-engineering

La manca d’aigua és un problema cabdal a moltes regions del món, i es preveu que ha d’empitjorar, tant en el nombre de gent que ho pateix, com en la seva intensitat. Una solució proposada és la regeneració de l’aigua, el qual consisteix a tractar aigua residual fins al punt a què es pot reutilitzar sense perjudici. Un mètode és la recàrrega d’aqüífer gestionada, acoblada al tractament per sòl d’aqüífer (MAR-SAT, per les sigles en anglès), que combinen la capacitat del sòl per a extreure contaminants amb el fet que el mateix sòl pot emmagatzemar aigua durant un temps considerable, i del qual es pot disposar en temps de falta. Per a investigar aquesta solució, s’ha construït una planta pilot a l’estació de depuració d’aigua residual (EDAR) a Palamós (Baix Empordà). El treball que es presenta se centrà en la caracterització hidràulica d’un dels sistemes d’aqüífer artificial a través d’una tomografia hidràulica. S’ha determinat que la conductivitat hidràulica del sistema és uniforme, en un rang de 1-10 m/d, el qual és coherent amb la predicció derivada de la seva relació empírica establerta amb la granulometria, i el classifica com a lleugerament permeable. També fou possible visualitzar la connectivitat hidràulica relativa, determinant que és generalment bona longitudinalment, i dolenta en secció. Per altra banda, un dels mecanismes clau darrere de l’atenuació de contaminants als aqüífers és la degradació de la matèria orgànica a través de reaccions redox. L’oxigen dissolt (OD) és un dels agents oxidants més forts dels que estan típicament disponibles en aquest context i, per aquest motiu, la concentració d’oxigen dissolt fou monitorada a quatre punts de l’aqüífer abans i durant l’execució de la tomografia hidràulica. S’han observat condicions anaeròbies ([OD] < 1 ppm) a tots els punts mostrats, i no s’ha pogut esclarir una relació clara entre la connectivitat hidràulica i el comportament de l’OD., La falta de agua es un problema importante en muchas regiones del mundo, y se prevé que tiene que empeorar, tanto en el número de gente que lo sufre, como en su intensidad. Una solución propuesta es la regeneración del agua, el cual consiste en tratar agua residual hasta el punto a que se puede reutilizar sin perjuicio. Un método es la recarga de acuífero gestionada, acoplada al tratamiento por suelo de acuífero (MAR-SAT, por las siglas en inglés), que combinan la capacidad del suelo para extraer contaminantes con el hecho que el mismo suelo puede almacenar agua durante un tiempo considerable, y del cual se puede disponer en tiempo de falta. Para investigar esta solución, se ha construido una planta piloto en la estación de depuración de agua residual (EDAR) en Palamós (Baix Empordà). El trabajo que se presenta se centró en la caracterización hidráulica de uno de los sistemas de acuífero artificial a través de una tomografía hidráulica. Se ha determinado que la conductividad hidráulica del sistema es uniforme, en un rango de 1-10 m/d, el cual es coherente con la predicción derivada de su relación empírica establecida con la granulometría, y lo clasifica como ligeramente permeable. También fue posible visualizar la conectividad hidráulica relativa, determinando que es generalmente buena, longitudinalmente, y mala en sección. Por otro lado, uno de los mecanismos clave detrás de la atenuación de contaminantes en los acuíferos es la degradación de la materia orgánica a través de reacciones redox. El oxígeno disuelto (OD) es uno de los agentes oxidantes más fuertes de los que están típicamente disponibles en este contexto y, por este motivo, la concentración de oxígeno disuelto fue monitorizada en cuatro puntos del acuífero antes y durante la ejecución de la tomografía hidráulica. Se han observado condiciones anaerobias ([OD] < 1 ppm) en todos los puntos mostrados, y no se ha podido esclarecer una relación clara entre la conectividad hidráulica y el comportamiento del OD, Water scarcity is a pressing issue in many regions of the globe and is predicted to become worse, both in terms of the number of people afflicted by it, and its intensity. A proposed solution is water reclamation, which involves treating wastewater to the extent that it can once more be used without prejudice. There are many ways that water reclamation can be achieved, but currently the most commonly employed methods are costly and energy-intensive. An alternative is Managed Aquifer Recharge coupled to Soil-Aquifer Treatment (MAR-SAT), which combines the innate capability of soil to remove pollutants with its capacity to store water for considerable lengths of time, making it accessible when needed. To investigate this solution, a pilot-scale test facility has been constructed in the wastewater treatment plant (WWTP) of Palamós (Catalonia, Spain). The work presented here was centred on characterising the hydraulics of one of the artificial aquifer systems via a hydraulic tomography. It was determined that the hydraulic conductivity across the system was uniform, in the range of 1-10 m/d, which is in line with the value predicted through its empirical relationship with grain-size, and classifies it as somewhat permeable. It was also possible to map the relative hydraulic connectivity, determining that it was generally good longitudinally, and relatively poor in the transverse direction. Additionally, one of the key mechanisms behind pollutant attenuation in aquifers is degradation of organic matter via redox reactions. Dissolved oxygen (DO) is the strongest oxidising agent typically available in this context, therefore the DO concentration was monitored at four sites in the aquifer before and during the hydraulic tomography. Anaerobic conditions ([DO] < 1 ppm) were observed across all probed sites, and no clear relationship between hydraulic connectivity and DO behaviour could be elucidated.

[EN] The acequias de careo are ancestral water channels excavated during the early Al-Andalus period (8th-10th centuries), which are used to recharge aquifers in the watersheds of the Sierra Nevada mountain range (Southeastern Spain). The water channels are maintained by local communities, and their main function is collecting snowmelt, but also runoff from rainfall from the headwaters of river basins and distributing it throughout the upper parts of the slopes. This method of aquifer artificial recharge extends the availability of water resources in the lowlands of the river basins during the dry season when there is almost no precipitation and water demand is higher. This study investigates the contribution of the careo channels in the watershed of Bérchules concerning the total aquifer recharge during the 2014-2015 hydrological year. Several channels were gauged, and the runoff data were compared with those obtained from a semi-distributed hydrological model applied to the same hydrological basin. The natural infiltration of meteoric waters accounted for 52% of the total recharge, while the remaining 48% corresponded to water transported and infiltrated by the careo channels. In other words, the careo recharge system enhances by 92% the natural recharge to the aquifer. Our results demonstrate the importance of this ancestral and efficient channel system for recharging slope aquifers developed in hard rocks. The acequias de careo are nature-based solutions for increasing water resources availability that have contributed to a prosperous life in the Sierra Nevada. Its long history (>1200 years) suggests that the system has remarkable resilience properties, which have allowed adaptation and permance for centuries in drastically changing climatic and socioeconomic conditions. This recharge system could also be applied to -or inspire similar adaptation measures in- semi-arid mountain areas around the world where it may help in mitigating climate change effects.

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

Agricultural managed aquifer recharge (AgMAR) is a strategy whereby surface water is used to intentionally flood croplands to recharge underlying aquifers. However, nitrate (NO3−) contamination in agriculturally intensive regions poses a threat to groundwater resources under AgMAR. We use a reactive transport model to understand the effects of AgMAR management strategies (i.e., by varying the frequency, duration between flooding events, and amount of water) on NO3− leaching to groundwater under different stratigraphic configurations and antecedent moisture conditions. We examine the potential of denitrification and nitrogen retention in deep vadose zone sediments (∼15 m) using variable AgMAR application rates on two-dimensional representations of differently textured soils, soils with discontinuous bands/channels, and with preferential flow paths characteristic of agricultural fields. Simulations indicate finer textured sediments, alone or embedded within/adjacent to high flow regions, are important reducing zones providing conditions needed for denitrification. Simulation results suggest that applying water all-at-once rather than in increments transports higher concentrations of NO3− deeper into the profile, which may exacerbate groundwater quality. This transport into deeper depths can be aggravated by wetter antecedent soil moisture conditions. However, applying water all-at-once also increases denitrification within the vadose zone by promoting anoxic conditions. We conclude that AgMAR can be designed to enhance denitrification in the subsurface and reduce NO3− leaching to groundwater, while specifically accounting for lithologic heterogeneity, antecedent soil moisture conditions, and depth to the water table. Our findings are potentially relevant to other systems that experience flooding inundation such as floodplains and dedicated recharge basins.

Push-pull tests (PPTs) were evaluated with 1-D radially axisymmetric multi-component geochemical reactive transport modelling (RTM) to assess aquifer reactivity controlling groundwater quality. Nutrient fate and redox processes were investigated in an Aquifer Storage and Recovery (ASR) system, in which oxic tile drainage water (TDW; nitrate ~14 mg/L; phosphate ~17 mg/L) was stored in an anoxic aquifer for later re-use as irrigation water. During the PPTs, the ASR system did not operate. PPTs were performed in two monitoring wells (MW2, MW3), with 1 m well screens in contrasting geochemical formations at different depths. In these wells, 300 L TDW was injected, and consecutively 720 L was abstracted within 12 days, during which water quality changes were studied. The RTM simulated cation exchange, precipitation of Hydrous Ferric Oxides, Iron (III)-phosphate and Calcium-phosphate minerals, and surface complexation as equilibrium processes. Oxidation of Pyrite, soil organic matter, and dissolved ferrous iron were simulated with kinetic rate expressions. Oxygen (within 2 days) and nitrate (within 4–7 days) were fully reduced during the PPTs. The main reductants were ferrous iron (Monitoring Well (MW) 2: 2%, MW3: 13%), soil organic matter (MW2: 93%, MW3: 6%), and Pyrite (MW2: 5%, MW3: 81%). The intra aquifer differences in dominant reduction pathways are remarkable as higher reduction rates coincided with lower contents of soil organic matter and Pyrite, respectively. Phosphate was mostly re-abstracted (MW2: 73%, MW3: 64%) and partially immobilized due to precipitation of Iron-hydroxyphosphates (MW2: 4.6%, MW3: 35%), Hydroxyapatite (MW2: 23%, MW3: 0%), and to a lesser extent by surface complexation on various minerals (MW2-3: <1%). The PPT-RTM approach enables a better understanding of reaction networks controlling water quality changes, and the reaction kinetics. PPT-RTM is a promising tool in exploratory studies or regular monitoring of water quality aspects of s, Sanitary Engineering

With aquifers around the world stressed by over-extraction, water managers are increasingly turning to managed aquifer recharge (MAR), directly replenishing groundwater resources through injection wells, recharge basins, or other approaches. While there has been progress in understanding the geological and infrastructure-related considerations to make MAR more effective, critical evaluations of its institutional design and implementation are limited. This study assesses MAR projects, using a case study of projects proposed by groundwater sustainability agencies (GSAs) in California to comply with the state's Sustainable Groundwater Management Act of 2014; these projects will almost double the number of MAR projects in the United States. We draw on content analysis of groundwater sustainability plans that propose these projects. We first assess the types of recharge projects proposed and the stated aims of the projects, to assess when and why agencies are turning to MAR as a solution. We find that recharge basins are by far the most common approach, and that GSAs hope these basins will improve water table levels, reduce subsidence, and improve water quality. We then analyze potential barriers to project implementation and assess the projects' ability to achieve the stated goals. Primary concerns identified include a potential lack of available water, a potentially challenging legal framework, and minimal consideration of funding and cumulative land needs. To conclude, we discuss broader considerations for ensuring that MAR is an effective water management tool.

To cope with water scarcity in drylands, stormwater is often collected in surface basins and subsequently stored in shallow aquifers via infiltration. These stormwater harvesting systems are often accompanied by high evaporation rates and hygiene problems. This is commonly a consequence of low infiltration rates, which are caused by clogging layers that form on top of the soil profile and the presence of a thick vadose zone. The present study aims to develop a conceptual solution to increase groundwater recharge rates in stormwater harvesting systems. The efficiency of vadose-zone wells and infiltration trenches is tested using analytical equations, numerical models, and sensitivity analyses. Dams built in the channel of ephemeral streams (wadis) are selected as a study case to construct the numerical simulations. The modelling demonstrated that vadose-zone wells and infiltration trenches contribute to effective bypassing of the clogging layer. By implementing these solutions, recharge begins 2250–8100% faster than via infiltration from the bed surface of the wadi reservoir. The sensitivity analysis showed that the recharge rates are especially responsive to well length and trench depth. In terms of recharge quantity, the well had the best performance; it can infiltrate up to 1642% more water than the reservoir, and between 336 and 825% more than the trench. Moreover, the well can yield the highest cumulative recharge per dollar and high recharge rates when there are limitations to the available area. The methods investigated here significantly increased recharge rates, providing practical solutions to enhance aquifer water storage in drylands.

The use of reclaimed water for agricultural irrigation is an increasingly common practice, which recently has found its own European regulatory frame. However, the partial removal of organic contaminants together with other xenobiotic substances in current wastewater treatment plants leads to the occurrence of residues of such pollutants in the treated effluents. Wastewater reclamation techniques are thus required to provide reclaimed water fitting the minimum quality standards set up for irrigation of crops intended for human consumption. This work describes the development and validation of a simple QuEChERS-based extraction and liquid chromatography quadrupole-linear ion trap mass spectrometry (LC-QqLIT-MS/MS) method for the simultaneous quantitative analysis of 55 pharmaceuticals and personal care products (PPCPs) in lettuces irrigated with treated wastewater and reclaimed water. The method showed good recovery rates (80-120%) and low detection limits (0.04-0.8 ng/g dw). In comparison with previous analytical methodologies, this method was simpler, faster and, in most cases, more sensitive. Moreover, is the first one analysing selected personal care products in lettuces. The proposed method was applied to assess the potential transfer of contaminants of urban origin in the use of reclaimed water in agriculture. The case study consisted of the evaluation of the lettuce uptake of the selected contaminants at field scale under two irrigation systems, two soil compositions, and two water types. Benzophenone-2, 4-hydroxybenzophenone, 1H-benzotriazole, 2-(2-Benzotriazol-2-yl)-p-cresol, nalidixic acid, diclofenac, carbamazepine 10,11-epoxy, N-des-methylvenlafaxine, and salicylic acid were transferred to all samples. Highest detected values corresponded to 4-hydroxybenzophenone (84.1 ng/g dw), benzophenone-2 (54.4 ng/g dw), and salicylic acid (53.8 ng/g dw). The best combination to minimize the transfer of the target contaminants from the irrigation water to the lettuce

The state of Arizona utilizes a valuable water management tool, Managed AquiferRecharge (MAR), in response to water scarcity and population growth. MAR consists of storing water in an aquifer through a process called artificial recharge. This research analyzes three different aspects of MAR in Central Arizona: a tool called long-term storage credits (LTSCs), a mechanism called the Central Arizona Groundwater Replenishment District (CAGRD), and means for recharge: the reuse of effluent. This research follows a three-article dissertation format. The main body of this dissertation is contained in Appendixes A, B, and C. Appendix A offers a descriptive analysis of sales and purchases of LTSCs and connects LTSCs to Arizona's laws and regulations that ensure sustainable use of water in the most populated areas of the state. LTSCs represent a quantity of water stored in the aquifer. Using data collected and maintained by the Arizona Department of Water Resources (ADWR), this study examines sales of LTSCs to reveal patterns of marketbased transactions. Analysis of 23 years of public records shows several trends: (1) LTSC transactions have been increasing since 2003; (2) municipal water providers and investment firms have been active participants in LTSC transactions; (3) the greatest transaction volumes involve governmental entities established by state law with groundwater recharge and replenishment obligations. The experience with LTSCs in Arizona indicates that market mechanisms of transactions can be helpful in regions that need to facilitate economic growth despite water scarcity. Appendix B provides a problem structuring method for policy analysis. This article uses primary qualitative data acquired in the Fall of 2020 by interviewing sixteen 18 CAGRD experts to find alternatives to CAGRD problems. This article also produces statistical and qualitative analyses of 41 survey responses collected in the Summer of 2021 to gather Arizona stakeholder opinions about CAGRD. R

Worldwide, groundwater overdraft is one issue faced in urban and rural environments impacting water supply. Expansion of irrigated agriculture, changes in consumption habits, population growth, and urbanization are some causes of increased water consumption. In Mexico, 157 of 657 aquifers are overexploited, and 50 are affected by seawater intrusion in coastal areas. Considering that Mexico relies on groundwater, it is urgent to examine policies and programs to reduce groundwater extraction, create and enforce adequate quantity and quality standards, and develop a portfolio of alternatives to increase groundwater recharge. Managed Aquifer Recharge (MAR), using reclaimed water and stormwater, is a tool that can be implemented to augment water recharge in overexploited aquifers. MAR helps to provide water supply for human activities, agriculture, environmental services and is a tool for adaptation to climate change in semi-arid regions of Mexico. In this research, I present an overview of water recharge projects that have been conducted in Mexico in the last 20 years, their methods for recharge, water sources, geographical distribution, and the main results obtained for each project. This research follows a three-article dissertation format. The main body of this dissertation focuses on Appendixes 1, 2, and 3. I conducted three field trips, phone interviews, and online surveys to gather the data used in this research. The information collected was organized and analyzed using qualitative and quantitative methods. Appendix 1. An overview of Managed Aquifer Recharge in Mexico and its legal framework focuses on describing the type of MAR projects that have been designed in the last 20 years, the method used for recharge, their primary outcomes, and limitations. In addition, the opportunities and barriers that operators of these MAR projects face were analyzed and discussed. The main finding of this section of the study identifies that, beyond the technical issues that MAR

The absolute demand for water is increasing due to demographic, industrial, and agricultural growth. Meanwhile, local water resources are constrained based on climate and geology. The deployment of select technologies holds promise to enhance the sustainable use of groundwater resources. Groundwater mapping is an essential first step, to understand the subsurface landscape. This knowledge can then be practically applied to manage and increase groundwater recharge, and to reduce saline groundwater intrusion into freshwater aquifers. Improving water-use efficiency in the agriculture, household, and industrial sectors can increase utility from each available unit of groundwater. However, the net groundwater implications of irrigation efficiency improvements are complex, as “wasted” irrigation water often contributes to groundwater recharge. Technologies can be used to improve the quality of groundwater contaminated by salt, arsenic, fluoride, and organic pathogens. Finally, in regions suffering from economic water scarcity, improved technologies for creating wells and pumping groundwater can increase access to groundwater.

We are facing a global water crisis exacerbated by hydro-climatic extremes related to climate change. Water scarcity is expected to increasingly affect indigenous and marginalized populations. Supporting the sovereignty of indigenous and rural populations to create water secure futures through place-based knowledge, local management, and Community-based Adaptation (CBA) measures may help tackle this crisis. Zapotec communities in Oaxaca, Mexico have self-organized for collective action to use Managed Aquifer Recharge (MAR) to address water scarcity, resulting in a perceived increase of groundwater availability. Treating groundwater as a common-pool resource (CPR) within a sociohydrological system, the objectives of this paper are two-fold: (1) to explore how MAR may be implemented as a CBA measure, and (2) to understand what factors triggered and/or enabled the widespread implementation of MAR by Zapotec indigenous communities in the Valles Centrales of Oaxaca, Mexico. In doing so, we aim to get a better understanding of local processes while also furthering theories that relate to CBA, CPR, and sociohydrology. This paper was born from the desire of the Zapotec community members to share their experience and lessons learned so other drought-vulnerable communities might benefit.

In coastal areas, groundwater resources are under pressure. To ensure the sustainable provision of safe drinking water under these increasing pressures, groundwater resource management is essential. An important technology to increase the sustainably available groundwater is Managed Aquifer Recharge (MAR). In southwestern Bangladesh, drinking water provision is problematic, leading to the consumption of bacterial-polluted pond water or the consumption of arsenic or brackish groundwater. To overcome these drinking water problems, MAR has been piloted in the form of 99 small-scale, community-run systems. A large part of the thesis focusses on understanding the large variation in groundwater salinity in this data-poor region. This variation is first researched at a local scale, to develop a conceptual model of steering palaeo and present-day hydrological processes and geomorphological controls. Subsequently, this conceptual model is used to understand the relation between landscape features, hydrological processes and groundwater salinity at a regional scale. Next, the research focusses on assessing the attachment of users to their current, often unsafe water options via interviews. The last part of the study builds on the previous results to map the regional potential for MAR based on both social necessity and technical suitability. This study is the first to demonstrate the relation between landscape features, hydrological processes and groundwater salinity throughout southwestern Bangladesh. Additionally, the study utilizes and provides an innovative method to assess and map the socio-hydrogeological potential for MAR, which shows whether implementation should focus on either improving the acceptance of MAR or on overcoming anticipated technical challenges, or on both. The findings and methodology of the study can be used for predicting the occurrence of valuable fresh groundwater and the socio-hydrogeological potential of MAR in coastal areas wor

In this article, we link NGO-supplied drinking water infrastructure projects with collective action development approaches. Although governing local, shared drinking water systems (DWS) requires users to act collectively, users rarely organize such collective action successfully by themselves. Non-governmental organizations (NGOs) are therefore frequently called upon to support local communities to set up or consolidate the kind of local collective action required for governing DWSs. However, the effectiveness of such forms of NGO support remains unclear. Therefore, this paper attempts to assess the form and impact of this kind of NGO support. Combining insights gained from theory on institutions for collective action in the context of shared resource systems, we develop a set of requirements presumed necessary for guaranteeing both day-to-day and long-term collective action among local shared DWS users. We apply this framework to empirically explore if, how and why NGO support targets these requirements, and whether this support influences users’ capacity for collective action. To this end we examine 11 cases where NGOs have worked with users of Managed Aquifer Recharge (MAR) systems in Bangladesh. We collected data through focus group discussions, semi-structured interviews with local leaders, NGO officials, and project staff, and by reviewing project documentation. We find that NGO support favors long-term requirements over the requirements for day-to-day collective action. NGO activities seem based on applying standard approaches to training and awareness raising, and less on empowering users to craft their own solutions. A case for a lasting impact of NGO support on any of the requirements is hard to make. Our results imply that when attempting to organize effective and long-lasting forms of collective action among the users of shared resource systems, both NGOs and commissioners of projects need to engage more explicitly in learning what works and what doesn’t