Mapping uncertainty in managed aquifer recharge potential across unconfined and confined aquifers of the Murray-Darling Basin

Managed aquifer recharge (MAR) is essential for enhancing groundwater storage and ensuring long-term water sustainability, particularly in semiarid regions. This study focuses on identifying and mapping suitable MAR areas in the Chiba watershed, Tunisia, by integrating hydrogeophysical, hydrological, and socioeconomic criteria. The methodology combines geographical information systems (GISs), multicriteria decision analysis (MCDA), and hydrological modeling. A stakeholder-driven analytical hierarchical process (AHP) is used to assess the MAR suitability criteria. To capture seasonal variability, the feasibility assessment is conducted separately for wet and dry periods. Three thematic layers are considered: the intrinsic hydrogeophysical conditions of the site (IS), water availability (WA), and water demand (WD). The results indicate that water availability is the dominant factor (49.3%), followed by water demand (30%) and site conditions (20%). MAR feasibility maps show that areas classified ‘highly’ to ‘very highly feasible’ represent 19% of the total watershed area. The maps highlight also the coastal areas as highly suitable because of their optimal hydrogeological characteristics, surplus water resources, and high agricultural and ecological demands. In contrast, upstream areas are less feasible because of their limited recharge potential and lower water availability. The maps also suggest specific MAR typologies, such as using treated wastewater in coastal areas and infiltration basins upstream. In conclusion, this study provides a replicable framework for integrating MAR into water policies by aligning site selection with recharge objectives, available water sources, and socioeconomic factors. The findings emphasize the critical role of stakeholder engagement in MAR planning and its embedding in existing water policies, providing a replicable framework for improving groundwater management in semiarid regions.HighlightsManaged aquifer recharge (MAR) suitable areas are identified and mapped.A participatory decision-making process is proposed to select feasible MAR areas.MAR-related criteria are grouped into three thematic layers.The recharge problem is formulated in terms of MAR typology.Stakeholders are engaged in different components of the decision-making process.

Managed aquifer recharge (MAR) is a promising adaptation measure to reduce vulnerability to climate change and hydrological variability. However, in areas where the basin is highly polluted, densely populated, and intensely cultivated, implementing suitable MAR strategies is a significant challenge. This study used a geographic information system-based multicriteria decision analysis (GIS-MCDA) approach to delineate the MAR potential sites using seven thematic layers describing surface and subsurface features. Further, basin-specific MAR approach was developed using information such as polluted water areas, canal network distribution for water supply, and cropping patterns. The results of this study indicate that only 17% of the area is highly suitable, while 54% and 29% were found moderately suitable and unsuitable for the MAR approach. Since most highly and moderately suitable sites were falling in the agricultural areas, agricultural-based MAR (AgMAR) was considered a preferred option. AquaCrop model for sugarcane was developed considering excess canal water supply during the grand growth stage to understand the AgMAR potential in the study area. It was observed that the potential recharge under normal irrigation scenarios varies from 135.5 to 272mm/year, which can be increased through AgMAR up to 545mm/year depending on the water availability for excess irrigations. This study provides an improved understanding of the parameters that should be considered for MAR site selection and post-GIS-MCDA analysis to assess the basin-specific MAR strategy.

Mapping the spatial distribution of chloride deposition across Australia

Widespread groundwater overdraft in alluvial aquifer systems like the Central Valley (CV) in California, USA, has increased interest in managed aquifer recharge (MAR). Like most clastic sedimentary basins, recharge to the productive semi-confined CV aquifer system remains a challenge due to the presence of nearly ubiquitous, multiple confining units (silt and clay) that limit recharge pathways. Previous studies suggest the presence of interconnected networks of coarse-texture sand and gravel deposits that bypass regional confining units over a small fraction of the CV near the American and Cosumnes rivers. Here, variably saturated infiltration and recharge processes were simulated across a domain that includes high-resolution representation of the heterogeneous alluvial geologic architecture in this area. Results show that recharge potential is highly dependent on subsurface geologic architecture, with a nearly 2 order-of-magnitude range of recharge across the domain. Where interconnected coarse-texture recharge pathways occur, results show that these features can (1) accommodate rapid, high-volume MAR and (2) propagate widespread and rapid pressure responses over multi-kilometer distances in the semi-confined aquifer system. For all MAR simulations, results show that the majority of MAR is accommodated by filling unsaturated-zone (UZ) pore volume. Results also show that coarse-texture UZ facies (where present) accommodate the majority of MAR volume during early time, but fine-texture facies ultimately accommodate the majority of the total MAR volume, even for coarse-dominated sites. These findings highlight the large variability of MAR potential across the landscape and demonstrate the importance of fine-texture facies for accommodating MAR in alluvial aquifer systems.

<p>Increasing aquifers' recharge and storage is of great importance in addressing challenges posed by climate change and growing water demand. Managed Aquifer Recharge (MAR) technologies may ensure water supply for agriculture and diminish impacts from groundwater overexploitation. The expansion of MAR solutions in Europe still requires the implementation of these waterworks at their maximum efficiency. Physical clogging is one of the main bottlenecks for these technologies. In spreading methods, during water recharge, eroded clays from surface runoff reach the infiltrating surface and intrude into the soil matrix, decreasing the basin infiltration capacity over time. The resulting loss in performance increases the operation and maintenance (O&M) costs and, in extreme cases, can lead to the MAR site's abandonment. Thus, it is vital to assess the risk of physical clogging during the MAR planning phase, extending the MAR scheme lifespan and minimising O&M costs. Our study aims to develop a comprehensive model for physical clogging transferable to multiple MAR sites, based on the characterisation of the sediment matrix and MAR operations. To achieve this, we built a semi-empirical 1D numerical model for physical clogging. Evolution in soil permeability via the Kozeny-Carman equation is computed in function of depth based on the input of fines into the soil matrix and the porous media characteristics. The vertical distribution of fines is derived through a general relationship from a systematic review of multiple studies in the literature. The model allows computing the evolution in infiltration rates over time for the MAR site and the depth of soil to be treated to restore infiltration efficiency. Preliminary validation at the field scale is conducted at a MAR infiltration basin in Suvereto, Italy. To spatially apply the model, zoning is performed through an electromagnetic induction (EMI) survey, defining areas with similar soil properties. Values of hydraulic conductivity near saturation and soil samples were collected to characterise the sediment matrix and fines content for the entire basin. Predictions of the expected decrease in infiltration capacity for spreading methods assists maintenance scheduling and reduce O&M costs for the specific site. The proposed model for physical clogging can serve as a tool for decision support when exploring a set of design alternatives prior to MAR construction.</p>

ABSTRACTMilpa Alta, located southeast of Mexico City, is a key region for environmental sustainability due to its volcanic soil, biodiversity, and critical role in aquifer recharge, which supports the city's water supply. However, rapid urbanization has severely impacted the area, causing reduced vegetation cover, increased runoff, and diminished groundwater recharge, which intensify flooding, soil erosion, and water scarcity. This study aims to identify optimal sites for managed aquifer recharge (MAR) structures in Milpa Alta through a multi‐criteria analysis incorporating criteria such as topography, land use, proximity to urban areas, and drainage networks. Uniquely, hydraulic simulations of flood scenarios were integrated into the analysis to improve the precision of site selection. Geographic information systems (GIS) were used to assess and combine these criteria, providing a spatial evaluation of suitability. Results indicate that the central and northern regions of Milpa Alta, particularly around San Francisco Tecoxpa and San Antonio Tecómitl, are most suitable for MAR implementation due to their permeable soils, gentle slopes, and proximity to agricultural lands and drainage networks. These MAR structures can enhance groundwater recharge and mitigate flood risks during extreme rainfall events, with the potential to capture up to 300,000 m3 of surface runoff during a single high‐intensity storm event. Despite its strengths, the study acknowledges limitations such as the absence of detailed water quality analyses and the need for sensitivity testing of the criteria weighting. This research provides an innovative approach to MAR site selection by integrating flood simulations, offering a replicable model for similar regions. Successful implementation of MAR in Milpa Alta requires addressing water quality concerns, engaging stakeholders, and ensuring compliance with regulatory frameworks. The findings emphasize MAR's potential to balance urbanization pressures with sustainable water management and flood mitigation strategies in Mexico City's rapidly developing areas.

Synthesis of research findings and general criteria for sustainable groundwater recharge and recovery in saline aquifers

<p>Groundwater is depleting across the globe. According to NASA, 33% of the world’s major basins are overexploited. This water shortage could be alleviated by using Managed aquifer recharge (MAR)  techniques. MAR is defined by Gale, 2005 as “Intentional storage and treatment of water in aquifers”. The three most common methods of MAR are a) direct infiltration into the aquifer through wells, b) interception in the river bed, c) indirect infiltration from the land surface (Dillon et al., 2009a). Baluchistan, the largest province of Pakistan by area (44 % of the total area of Pakistan) has hyper-arid to dry climate and is comprised of 18 river basins, 11 of which are suffering from groundwater depletion (2-3 m cumulative decline in watertable) . To solve the issue, 300 delay action dams were constructed but due to high-intensity rainfalls, steep slopes, and lack of vegetative cover, the sediment erosion rate was very high which converted the delay action dams into evaporation ponds and this scheme failed. After the failure of delay action dams, the leaky dam technique along with effective watershed management was applied, this enhanced the percolation and reduced the sedimentation in the reservoir (Asharaf and Sheikh 2017). Leaky dams reduce the energy of flood, initiate the sedimentation of suspended load and release the water downstream through leakage to infiltrate in the riverbed (Gale, 2005). The integrated approach of watershed management, leaky dams, ditches, and furrows positively affected the watertable in the area (Asharaf and Sheikh, 2017). The goals of this research are to revise the development of MAR in Baluchistan (Pakistan), to display a MAR suitability map using INOWAS platform and update of MAR sites in Baluchistan at Global MAR portal. To delineate potential MAR sites, thematic layers such as slope, rainfall, drainage, land cover, and soil characteristics are integrated using GIS multi-criteria decision analysis (based on weighted linear combination method) (Senanayake et al, 2016).  MAR suitability maps are used as a preliminary step to field investigation to decide whether an area is suitable for a particular MAR type and hold the potential to be integrated into sustainable groundwater management plans . This study helps design a suitable groundwater management plan for Baluchistan.</p><p><strong>Acknowledgement:</strong></p><p>"This work is part of a project that has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 810980."</p><p> </p><p>References</p><ul><li> Dillon, P., I. Gale, S. Contreras, P. Pavelic, R. Evans & J. Ward. (2009a), Managing aquifer recharge and discharge to sustain irrigation livelihoods under water scarcity and climate change. IAHS Publication 330, pp.1-12</li> <li> Gale, I. (2005). Strategies for Managed Aquifer Recharge (MAR) in semi-arid areas.UNESCO</li> <li> M.Ashraf and Ashfaq A. Sheikh (2017). Sustainable Groundwater Management in Balochistan. Pakistan Council of Research in Water Resources (PCRWR), pp. 34.</li> <li> Senanayake, I.P., Dissanayake, D.M.D.O.K., Mayadunna, B.B., Weerasekera, W.L.,( 2016). An approach to delineate groundwater recharge potential sites in Ambalantota, Sri Lanka using GIS techniques. Geoscience Frontiers, Special Issue: Progress of Machine Learning in Geosciences 7, 115–124.</li> </ul>

Evaluating the feasibility of Managed Aquifer Recharge techniques as a drought mitigation strategy for the Seville water supply system (southern Spain).

Managed aquifer recharge (MAR) provides a sustainable method to store large volumes of water. However, uncertainties around the associated risks, initial costs and regulatory regime are key influences on its development in the UK. This paper reports a critical review of available risk management frameworks as a first step towards the development of an assessment framework suitable for MAR schemes in the UK. Classification of risks across the MAR process involved deconstructing the process into functional elements; pre-treatment, recharge, storage, recovery, and post-treatment prior to final use, with each element presenting a range of risks to different receptors. An initial listing of seven potential frameworks were reduced to three (hazard and critical control point analysis, the world health organisation’s water safety plans and the Australian guidelines for water recycling using MAR) for detailed assessment. Although the hazard and critical control point analysis and the water safety plans may be adapted for use in MAR, they do not provide specific guidance for potential risks associated with aquifer recharge schemes. Furthermore, neither of them adequately addresses the risks associated with the recharge, storage and recovery elements of a scheme. The Australian guidelines provide guidance specific to MAR and are particularly effective in considering risk to these elements. The main conclusion is that although the Australian guidelines focus on potential hazards and might thereby not be suitable for identifying more process oriented considerations, they do constitute a robust basis for developing a framework for risk management for MAR schemes in the UK.

The Walla Walla Basin in Eastern Oregon and Washington, USA, faces challenges in sustaining agricultural water supplies and endangered fisheries in the Walla Walla River (WWR). 11.1 Mm3/year of managed aquifer recharge (MAR) is currently used in the basin to supplement groundwater with the goal of maximizing instream flow during dry summer months. A numerical groundwater–surface water model was calibrated to observed hydrological conditions and applied to predict future conditions under current management practices (baseline model) and for four alternative water management scenarios. These scenarios were developed to predict how lining canals to eliminate seepage losses and concurrently reducing irrigation diversions from the WWR will impact stream flows and groundwater storage with varying levels of MAR. Model results predict that seasonal low flows in the WWR at the downstream reference location will increase an average of 0.13 m3/s relative to baseline conditions due to instream water savings with conversion of unlined canals to pipelines (Current MAR-Piped). With MAR increased to 18.0 and 29.9 Mm3/year and an additional 58 km piping (Increased MAR-Piped and Maximum MAR-Piped scenarios), the predicted flow increases in the WWR-averaged 0.16 and 0.26 m3/s, respectively. Without MAR (No MAR-Piped), flow is predicted to decrease for the months of August and September relative to baseline conditions. The “No MAR-Piped” and “Current MAR-Piped” scenarios are predicted to reduce groundwater storage relative to the baseline model due to reduced canal seepage. The “Maximum MAR-Piped” scenario is predicted to yield groundwater storage that is greater than baseline conditions, while groundwater storage is predicted to be similar to baseline conditions in the “Increased MAR-Piped” scenario. Model results indicate that canal piping in combination with increased MAR can allow for increased summer flows in the WWR while stabilizing groundwater storage levels for agricultural use and ecological benefits; whereas lining canals without MAR would be detrimental to environmental flows in the WWR and its tributaries.

The increasing demands for food and renewable energy are placing unprecedented pressure on water and land resources, a challenge further exacerbated by climate-induced declines in surface water availability. Globally widespread cropland abandonment presents a unique opportunity for strategic, multi-benefit land repurposing to enhance sustainable water, food, and energy management. Managed Aquifer Recharge (MAR) offers a promising strategy to augment groundwater supplies for agriculture and ecosystems, while water-efficient variable renewable energy (VRE), such as wind power and solar photovoltaic (PV), offers potential to reduce surface water use for hydropower, allowing more water allocation for irrigation and MAR. Despite these promising synergies, the large-scale feasibility and socio-economic value of integrating MAR and VRE development on abandoned cropland remain unclear. In this study, we develop a multi-scale spatial optimization framework to identify priority locations for MAR and VRE expansion, aiming to enhance water, food, and energy security, particularly during droughts. We evaluate the benefits and trade-offs of repurposing global abandoned cropland under various strategies (i.e., MAR only, VRE only, and integrated MAR-VRE) across different climate conditions and spatial scales (local, regional, and global). Our findings highlight that multi-objective spatial optimization and cross-scale coordination are crucial for maximizing synergies and minimizing conflicts between MAR and VRE development. Our study reveals the untapped potential of abandoned cropland for water and energy expansion and proposes a scalable framework to support multi-benefit land management strategies that boost water-food-energy sustainability.

<p>Vis, a small remote island in the Adriatic Sea, inhabited since the time of ancient Greeks and Romans, exhibits a unique historical and natural environment. With an area of 89.7 km<sup>2</sup>, the island is mostly composed of karstified carbonate rocks and belongs to Dinaric karst region, locus typicus for karst landforms. Its distance from the mainland is around 50 km from the city of Split, 147 km from the Italian coastline and 18 km from neighbouring Hvar island. The climate on the island is Mediterranean with dry and hot summer and mild, rainy and humid winter (Csa). Vis island, due to its remote location, is not connected to the mainland by submarine water pipeline so it has autonomous water supply due to favourable geological and hydrological conditions which enabled the formation of excellent karst aquifers. The majority of water is abstracted from drilled wells in the central part of the island (Korita extraction site), around 40 l/s, while additional quantities are obtained from coastal spring of Pizdica. Although predominantly of good quality, existing groundwater quantities on Vis are extremely vulnerable to the effects of climate change, namely increase in temperature, quantitative and temporal variability in precipitation trends as well as seawater intrusion. Moreover, Vis island is an attractive location for summer bathing tourism which causes the highest pressure on drinking water resources precisely during the hydrological minimum. An idea to apply artificial recharge of karst aquifer on Vis emerged during the 1970s, however, only on the theoretical level.</p><p>Through the scope of the DEEPWATER-CE project, funded by Interreg Central Europe Programme, the aim is to develop implementation frame for managed aquifer recharge (MAR) solutions. Simplified, MAR is a process by which excess surface water is directed into the ground — either by spreading on the surface, by using recharge wells, or by altering natural conditions to increase infiltration to replenish an aquifer (DILLON et al., 2019). Globally, various designs of MAR schemes have successfully been implemented in unconsolidated aquifers, but there is little experience with artificially recharging karst aquifers (ROLF, 2017). A particular challenge for the technical implementation and operation of MAR is posed by strong hydraulic anisotropy and heterogeneity of karst aquifers and by their high vulnerability to contamination (XANKE, 2017). To investigate whether a MAR operation is feasible and suitable for karst aquifer on Vis, a detailed field and laboratory investigations were carried out. Field investigations included in-situ measurements of physicochemical parameters on water samples from springs and boreholes, groundwater monitoring (conductivity, temperature and water levels), geophysical methods (ERT, magnetotellurics, and seismic refraction) and structural measurements. Laboratory analyses included measurements of stabile water isotopes, and principal cations and anions. Hence, by conducting extensive investigations, coupled with historical data and previous research, a foundation for implementing efficient and sustainable management of karst aquifer through MAR on Vis island will be provided. </p>

Enhancing groundwater recharge in drinking water protection zones in Flanders (Belgium): A novel approach to assess stormwater managed aquifer recharge potential

ABSTRACTWater banking in aquifers is an internationally proven, low-cost solution that could improve drought resilience across the Murray Darling Basin. While significant potential for water banking through managed aquifer recharge (MAR) or conjunctive use of surface and groundwater resources has been identified in the Murray Darling Basin Plan, there is a need to establish clear policy and institutional foundations to incentivise adoption. To provide appropriate incentives for schemes, the legal status of rights to recharge, store and recover water, and the rules and costs which apply to groundwater extraction need to be clear and transparent. This paper aims to clarify principles and frameworks to secure water rights for recharge, storage, and recovery within the sustainable limits of water resources currently set under law. The current Basin Plan supports water banking, and banking would be complementary with objective and outcomes sought by future Basin Plans. Existing water accounting systems would need to accommodate this new capacity. Institutional arrangements and financial structures of water banking in the USA provide guidance for Australia. Demonstration sites would enable concurrent policy development and institutional set-up and provide critical experience to serve as models for wider adoption as part of future Murray Darling Basin plans.