Managed Aquifer Recharge Operations Research Articles

Multi-Facet analysis of analytical and numerical models to resolve sustainable artificial recharge rates in unconfined aquifers

Managed aquifer recharge (MAR) has emerged as a potential solution to resolve water insecurity, globally. However, integrated studies quantifying the surplus source water, suitable recharge sites and safe recharge capacity is limited. In this study, a novel methodology is presented to quantify transient injection rates in unconfined aquifers and generate MAR suitability maps based on estimated surplus water and permissible aquifer recharge capacity (PARC). Subbasin scale monthly surplus surface runoff was estimated at 75% dependability using a SWAT model. A linear regression model based on numerical solution was used to capture the aquifer response to injection and to calculate PARC values at subbasin level. The available surplus runoff and PARC values was then used to determine the suitable site and recharge rate during MAR operation. The developed methodology was applied in the semi-arid region of Lower Betwa River Basin (LBRB), India. The estimated surplus runoff was generally confined to the monsoon months of June to September and exhibited spatial heterogeneity with an average runoff rate of 5000 m3/d in 85% of the LBRB. Analysis of the PARC results revealed that thick alluvial aquifers had large permissible storage capacity and about 50% of the LBRB was capable of storing over 3500 m3/d of water. This study revealed that sufficient surplus runoff was generated in the LBRB, but it lacked the adequate safe aquifer storage capacity to conserve it. A total 65 subbasins was identified as the best suited sites for MAR which had enough surplus water and storage capacity to suffice 20% of the total water demand in the LBRB. The developed methodology was computationally efficient, could augment the field problem of determining scheduled recharge rates and could be used as a decision-making tool in artificial recharge projects.

Introducing a tailored site delineation approach to optimize the design of managed aquifer recharge surface spreading infrastructure

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, scale of MAR schemes, 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 complex geology, thereby reducing water costs, minimizing the environmental impact of infrastructure construction, and reducing land use conflicts.

Managed aquifer recharge as a strategy to redistribute excess surface flow to baseflow in snowmelt hydrologic regimes

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

Groundwater and surface water nitrate pollution in an intensively irrigated system: Sources, dynamics and adaptation to climate change

Freshwater pollution by nitrate is a major threat to human and ecosystem health. Basin-scale studies on nitrate pollution generally focus separately on surface water or on groundwater bodies, thus the role played by their interaction on nitrate concentrations, possibly including also agricultural irrigation, is often overlooked and so is addressed here in the intensively irrigated hydro-system of the Oglio River basin (Northern Italy). Tracers of groundwater recharge (stable water isotopes and Cl/Br ratio) together with nitrate and boron stable isotopes indicate that the main source of the diffuse nitrate pollution affecting groundwater resources in the area is related to agricultural activities and, locally, to untreated civil/industrial effluents. Moreover, these data reveal the strong control of irrigation return flow on groundwater nitrate concentrations, with contrasting effects: groundwater-fed irrigation promotes higher concentrations due to the recirculation of high-NO3 groundwater, whereas intensive surface-water-irrigation, fed by low-NO3 river water, generates lower concentrations due to dilution. The control of irrigation return flow on groundwater nitrate links nitrate pollution and climate change: if surface-water-irrigation will be abandoned, as a consequence of intensified summer droughts, in favor of groundwater-fed irrigation, an increase in groundwater nitrates is expected due to a basin-scale groundwater recirculation and the cessation of the dilution effect. In addition to the reduction of the N input to soils from fertilizers, i.e., the sole pollution mitigation strategy able to solve the problem, an adaptation strategy to climate change might be the implementation, during non-irrigation rainy periods, of managed aquifer recharge operations, such as the so-called “forested infiltration areas”, to take advantage of water abundancy from rivers under high-flow conditions, thus combining a supplement on groundwater recharge with the beneficial dilution effect on dissolved nitrate.

Response of groundwater quality to river-aquifer interactions during managed aquifer recharge: A reactive transport modeling analysis

Managed aquifer recharge (MAR) has been applied for groundwater restoration as an effective strategy in many overdraft regions. In Jinan, China, MAR through river infiltration was conducted regularly in recent years because of the most famous spring groups’ drying up due to continuous decline of groundwater level caused by extensive pumping. A substantial rise of water table (∼20 m) has been observed near the river, however, the potential change in groundwater quality and geochemistry during MAR process remains unknown. In this study, a flow and multi-component reactive transport model was developed to evaluate the impact of MAR on chemical reaction processes and the response of groundwater quality to the interaction of river water and groundwater. The geochemical conditions of the river water and groundwater are significantly different, as river water contained more dissolved organic carbon (DOC) and less nitrate than groundwater did in the study area with intensive agricultural activity. This study revealed that nitrate dilution rather than denitrification was the main process responsible for observed groundwater quality change during MAR. Preferential flow occurring in the aquifer resulted in strong spatial variability of nitrate concentrations in the groundwater. River water DOC, aquifer hydraulic conductivity distribution, and river-aquifer hydrodynamic conditions can all affect the redox condition in the riparian zone by changing either reaction rate or residence time. The results from this study indicate that groundwater geochemistry can be significantly altered during MAR, suggesting the importance of regular monitoring plan to assess the changes in groundwater quality, especially in the area where river sediments are rich in organic carbon. Such monitoring and reactive transport modeling analysis is critical to ensuring that the adverse impact on groundwater quality by potential MAR operations be kept to a minimum.

A numerical assessment on the managed aquifer recharge to achieve sustainable groundwater development in Chaobai River area, Beijing, China

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.

A review on risk assessment in managed aquifer recharge

Managed aquifer recharge (MAR) refers to a suite of methods that is increasingly being applied worldwide for sustainable groundwater management to tackle drinking or irrigation water shortage or to restore and maintain groundwater ecosystems. The potential for MAR is far from being exhausted, not only due to geological and hydrogeological conditions or technical and economic feasibility but also due to its lack of acceptance by the public and policymakers. One approach to enable the safe and accepted use of MAR could be to provide comprehensive risk management, including the identification, analysis, and evaluation of potential risks related to MAR. This article reviews current MAR risk assessment methodologies and guidelines and summarizes possible hazards and related processes. It may help planners and operators select the appropriate MAR risk assessment approaches and support the risk identification process. In addition to risk assessment (and subsequent risk treatment) related to the MAR implementation phase, this review also addresses risk assessment for MAR operation. We also highlight the limitations and lessons learned from the application and development of risk assessment methodologies. Moreover, developments are recommended in the area of MAR-related risk assessment methodologies and regulation. Depending on data availability, collected methodologies may be applicable for MAR sites worldwide. Integr Environ Assess Manag 2022;18:1513-1529. © 2022 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Using Heat as a Tracer to Detect the Development of the Recharge Bulb in Managed Aquifer Recharge Schemes

Managed Aquifer Recharge (MAR), the intentional recharge of aquifers, has surged worldwide in the last 60 years as one of the options to preserve and increase water resources availability. However, estimating the extent of the area impacted by the recharge operations is not an obvious task. In this descriptive study, we monitored the spatiotemporal variation of the groundwater temperature in a phreatic aquifer before and during MAR operations, for 15 days, at the LIFE REWAT pilot infiltration basin using surface water as recharge source. The study was carried out in the winter season, taking advantage of the existing marked difference in temperature between the surface water (cold, between 8 and 13 °C, and in quasi-equilibrium with the air temperature) and the groundwater temperature, ranging between 10 and 18 °C. This difference in heat carried by groundwater was then used as a tracer. Results show that in the experiment the cold infiltrated surface water moved through the aquifer, allowing us to identify the development and extension in two dimensions of the recharge plume resulting from the MAR infiltration basin operations. Forced convection is the dominant heat transport mechanism. Further data, to be gathered at high frequency, and modeling analyses using the heat distribution at different depths are needed to identify the evolution of the recharge bulb in the three-dimensional space.

Managed aquifer recharge as a drought mitigation strategy in heavily-stressed aquifers

Increasing meteorological drought frequency and rising water demand drive groundwater exploitation beyond sustainable limits. In heavily-stressed aquifers mitigation strategies, such as Managed Aquifer Recharge (MAR), are needed to restore depleted groundwater storage. MAR is also designed to overcome short dry periods. However, wider impacts of MAR as a drought mitigation strategy remain to be quantified. The objective of this study is to assess impacts of MAR in heavily-stressed aquifers using a case study of the Central Valley in California (USA). The novelty of this study lies in its analytical approach based on long-term observational data of precipitation, groundwater levels, and MAR operations. The impact of MAR operations is assessed regionally and for different temporal scales. Results show spatially-coherent clusters of groundwater level time series in the Central Valley representing three main patterns that manifest themselves in different groundwater drought characteristics and long-term trends. The first regional pattern shows lengthened groundwater droughts and declining groundwater levels over time, indicating effects of over abstraction in aquifer sections without MAR. The second regional pattern shows reduced groundwater drought duration and magnitude related to periodically rising groundwater levels, showing short-term MAR impacts. The third regional pattern shows alleviated groundwater droughts and groundwater levels show a long-term rise, representing long-term MAR impacts. Mitigated groundwater droughts and long-term rise in groundwater levels reveal the value of long-term MAR operations and their contribution toward sustainable groundwater management. Increased institutional support is recommended to ensure longevity of MAR and thereby amplify its success as regional drought mitigation strategy in heavily-stressed aquifers.

Deriving optimal operational policies for off-stream man-made reservoir considering conjunctive use of surface- and groundwater at the Bar dam reservoir (Iran)

Study regionThe off-stream artificial Bar lake, built in 2015 to store the flood flows of the Bar river for domestic and industrial needs and with the objective to intentionally recharge the aquifer, is situated in the Razavi Khorasan province (Iran). Study focusWe present a methodology, based on the combination of a MODFLOW groundwater flow model for estimating seepage rates, and an optimization model, for the management and operation of an artificial reservoir considering surface/groundwater interactions for satisfying 12 Mm3/year of water demand. We simulated the reliable amount of water that can be supplied from the reservoir, considering reservoir seepage, maximizing water supply yields subject to the water supply reliability requirements, and the additional intentional volume of groundwater recharge. New hydrological insights for the regionOur results demonstrate the reliability of conjunctive use of surface-and ground-water in water scarce areas by exploiting reservoir infrastructures with relevant leakage losses, also for creating additional aquifer storage. In such systems, man-induced changes of lake stages can significantly affect the volume of water that seeps through the lakebed. The aquifer, under managed aquifer recharge operations, may then provide the resource not satisfied by the reservoir release, fulfilling 100 % reliability of water supply. The conjunctive use of surface- and ground-water, by improving water security, may open new sustainability views for leaking reservoirs, even if they were not initially designed for increasing aquifer recharge, in many areas worldwide.

Application of QMRA to MAR operations for safe agricultural water reuses in coastal areas

A pathogenic Escherichia coli (E.coli) O157:H7 and O26:H11 dose-response model was set up for a quantitative microbial risk assessment (QMRA) of the waterborne diseases associated with managed aquifer recharge (MAR) practices in semiarid regions. The MAR facility at Forcatella (Southern Italy) was selected for the QMRA application. The target counts of pathogens incidentally exposed to hosts by eating contaminated raw crops or while bathing at beaches of the coastal area were determined by applying the Monte Carlo Markov Chain (MCMC) Bayesian method to the water sampling results. The MCMC provided the most probable pathogen count reaching the target and allowed for the minimization of the number of water samplings, and hence, reducing the associated costs. The sampling stations along the coast were positioned based on the results of a groundwater flow and pathogen transport model, which highlighted the preferential flow pathways of the transported E. coli in the fractured coastal aquifer. QMRA indicated tolerable (<10−6 DALY) health risks for bathing at beaches and irrigation with wastewater, with 0.4 infectious diseases per year (11.4% probability of occurrence) associated with the reuse of reclaimed water via soil irrigation even though exceeding the E. coli regulation limit of 10 CFU/100 mL by five times. The results show negligible health risk and insignificant impacts on the coastal water quality due to pathogenic E. coli in the wastewater used for MAR. However, droughts and reclaimed water quality can be considered the main issues of MAR practices in semiarid regions suggesting additional reclaimed water treatments and further stress-tests via QMRAs by considering more persistent pathogens than E. coli.

Potential for Managed Aquifer Recharge to Enhance Fish Habitat in a Regulated River

Managed aquifer recharge (MAR) is typically used to enhance the agricultural water supply but may also be promising to maintain summer streamflows and temperatures for cold-water fish. An existing aquifer model, water temperature data, and analysis of water administration were used to assess potential benefits of MAR to cold-water fisheries in Idaho’s Snake River. This highly-regulated river supports irrigated agriculture worth US $10 billion and recreational trout fisheries worth $100 million. The assessment focused on the Henry’s Fork Snake River, which receives groundwater from recharge incidental to irrigation and from MAR operations 8 km from the river, addressing (1) the quantity and timing of MAR-produced streamflow response, (2) the mechanism through which MAR increases streamflow, (3) whether groundwater inputs decrease the local stream temperature, and (4) the legal and administrative hurdles to using MAR for cold-water fisheries conservation in Idaho. The model estimated a long-term 4%–7% increase in summertime streamflow from annual MAR similar to that conducted in 2019. Water temperature observations confirmed that recharge increased streamflow via aquifer discharge rather than reduction in river losses to the aquifer. In addition, groundwater seeps created summer thermal refugia. Measured summer stream temperature at seeps was within the optimal temperature range for brown trout, averaging 14.4 °C, whereas ambient stream temperature exceeded 19 °C, the stress threshold for brown trout. Implementing MAR for fisheries conservation is challenged by administrative water rules and regulations. Well-developed and trusted water rights and water-transaction systems in Idaho and other western states enable MAR. However, in Idaho, conservation groups are unable to engage directly in water transactions, hampering MAR for fisheries protection.

Effects of Phosphate, Silicate, and Bicarbonate on Arsenopyrite Dissolution and Secondary Mineral Precipitation

Managed aquifer recharge (MAR) has been applied to meet quickly growing water demands. However, during MAR operations, the injected water can induce dissolution of local minerals and result in the ...

Statistical and geochemical fingerprinting analysis of arsenic mobilization and natural background associated with artificial groundwater recharge

Differentiation of anthropogenic water-quality impacts and natural water quality is an important consideration for water management, and is a common concern in the vicinity of managed aquifer recharge operations. Application of geochemical fingerprinting methods at a mine site in Nevada, USA allowed for groundwater monitoring wells that have been influenced by infiltration operations to be discriminated from groundwater with naturally elevated arsenic. Increasing arsenic concentrations are shown to correlate with the formation of a groundwater mound on the site. Following filtering of human-impacted water-quality records, a natural background concentration of arsenic in groundwater equal to 0.036 mg/L was calculated using statistical methods suited to non-parametric datasets. This calculated background concentration corresponds well to various observations on the site, where arsenic greater than the drinking water standard is ubiquitous. Results of empirical leach testing (Meteoric Water Mobility Procedure) were compared with temporal changes in arsenic concentrations in groundwater, and indicated that arsenic is likely leached from soils in the unsaturated zone and may be conservatively transported to the water table. The applied methodology allows for regulatory compliance to be easily evaluated and can be applied in a number of different environments aside from mining operations.

Regional-Scale Analysis of the Effect of Managed Aquifer Recharge on Saltwater Intrusion in Irrigated Coastal Aquifers: Long-Term Groundwater Observations and Model Simulations in NE Tunisia

Bachtouli, S. and Comte, J.-C., 2019. Regional-scale analysis of the effect of managed aquifer recharge on saltwater intrusion in irrigated coastal aquifers: Long-term groundwater observations and model simulations in NE Tunisia. Journal of Coastal Research, 35(1), 91–109. Coconut Creek (Florida), ISSN 0749-0208.In overexploited coastal aquifers threatened or affected by saline intrusion, managed aquifer recharge (MAR) is increasingly applied in the aim of maintaining or recovering freshwater quantity and quality. The long-term regionalscale effectiveness of MAR, however, lacks field examples. The Korba coastal aquifer (Tunisia) has been increasingly overexploited since the 1960s and intensively studied over the last few decades. Groundwater abstraction has resulted in a decline of groundwater levels and a dramatic increase in salinity through both lateral seawater intrusion and shallow salinization from irrigation. MAR strategies, including freshwater injection wells and sewage-water infiltration basins, have been progressively implemented since 1990. Using 50 years of groundwater head and salinity records, a regional three-dimensional numerical groundwater model is calibrated to study the spatiotemporal dynamics of groundwater salinization including the past and future impact of the MAR operations. Results suggest that lateral seawater intrusion from the coast and shallow infiltration of evapoconcentrated saline irrigation water are the two interlinked dominant regional processes of groundwater salinization, equivalent in magnitude. In accordance with the groundwater observations, simulated historical MAR operations are shown to have contributed to slowdown and stabilized the regional salinization, which contrasts with the steady rise that is obtained in the hypothetical absence of MAR. The future MAR simulation scenarios suggest that spatial management of irrigation supplies and injection points from dam freshwater has a potential for further reducing the salinization of shallow groundwater and potentially reversing the inland progression of the seawater front. Further works should look at reconciling modelling recommendations with management practice options.

Modeling colloid-associated atrazine transport in sand column based on managed aquifer recharge

The Yellow River with high silt concentration is the main source of domestic water supply for downstream cities. After desilting, 85% silt is removed but fine suspended particles remain in the water, which may cause health and environmental risks, and the traditional water treatment technology by a water plant is ineffective in removing fine suspended particles. Atrazine is one of eight priority-controlled trace organic pollutants in Yellow River water. As one of the effective measures, managed aquifer recharge (MAR) is adopted to improve the Yellow River water quality. The model of colloid-associated atrazine transport is simulated at laboratory scale. The migration experiment of atrazine in heterogeneous porous medium (non-uniformity coefficient of 25.2) with saturated and steady flow is conducted under sand washing condition. The observed data of breakthrough curves are numerically simulated using convection–dispersion equation and CXTFIT 2.1 software. Results show that in the absence of montmorillonite, atrazine reaches a peak at approximately 100 min, and the peak is 82% of the initial value; whereas in the presence of montmorillonite, atrazine reaches a peak at approximately 55 min. Thus, atrazine can be absorbed on colloidal particles and spread in the area, and the remaining atrazine aggravates the risk of pollution for groundwater environment. Therefore, preventive measures should be considered in the MAR system to reduce the exogenous colloid into the aquifer, it is significant for sustainable MAR operations. Equilibrium and non-equilibrium models can better fit the experimental data and can be utilized to analyze the colloid-assisted atrazine transport in saturated heterogeneous porous media under a steady state.

Nutrient Removal during Stormwater Aquifer Storage and Recovery in an Anoxic Carbonate Aquifer.

Stormwater harvesting coupled to managed aquifer recharge (MAR) provides a means to use the often wasted stormwater resource while also providing protection of the natural and built environment. Aquifers can act as a treatment barrier within a multiple-barrier approach to harvest and use urban stormwater. However, it remains challenging to assess the treatment performance of a MAR scheme due to the heterogeneity of aquifers and MAR operations, which in turn influences water treatment processes. This study uses a probabilistic method to evaluate aquifer treatment performance based on the removal of total organic C (TOC), N, and P during MAR with urban stormwater in an anoxic carbonate aquifer. Total organic C, N, and P are represented as stochastic variables and described by probability density functions (PDFs) for the "injectant" and "recovery"; these injectant and recovery PDFs are used to derive a theoretical MAR removal efficiency PDF. Four long-term MAR sites targeting one of two tertiary carbonate aquifers (T1 and T2) were used to describe the nutrient removal efficiencies. Removal of TOC and total N (TN) was dominated by redox processes, with median removal of TOC between 50 and 60% at all sites and TN from 40 to 50% at three sites with no change at the fourth. Total P removal due to filtration and sorption accounted for median removal of 29 to 53%. Thus, the statistical method was able to characterize the capacity of the anoxic carbonate aquifer treatment barrier for nutrient removal, which highlights that aquifers can be an effective long-term natural treatment option for management of water quality, as well as storage of urban stormwater.

Assessing the efficiency of a coastal Managed Aquifer Recharge (MAR) system in Cyprus

Managed Aquifer Recharge (MAR) is becoming an attractive water management option, with more than 223 sites operating in European countries. The quality of the produced water, available for drinking or irrigation processes is strongly depended on the aquifer's hydrogeochemical characteristics and on the MAR system design and operation. The objective of this project is the assessment of the operation efficiency of a MAR system in Cyprus. The coupling of alternative methodologies is used such as water quality monitoring, micro-scale sediment sorption experiments, simulation of groundwater flow and phosphate and copper transport in the subsurface using the FEFLOW model and evaluation of the observed change in the chemical composition of water due to mixing using the geochemical model PHREEQC. The above methodology is tested in the Ezousa MAR project in Cyprus, where treated effluent from the Paphos Waste Water Treatment Plant, is recharged into the aquifer through five sets of artificial ponds along the riverbed. Additionally, groundwater is pumped for irrigation purposes from wells located nearby. A slight attenuation of nutrients is observed, whereas copper in groundwater is overcoming the EPA standards. The FEFLOW simulations reveal no effective mixing in some intermediate infiltration ponds, which is validated by the inverse modeling simulation of the PHREEQC model. Based on the results, better control of the infiltration capacity of some of the ponds and increased travel times are some suggestions that could improve the efficiency of the system.

Monitoring and modeling infiltration–recharge dynamics of managed aquifer recharge with desalinated seawater

Abstract. We study the relation between surface infiltration and groundwater recharge during managed aquifer recharge (MAR) with desalinated seawater in an infiltration pond, at the Menashe site that overlies the northern part of the Israeli Coastal Aquifer. We monitor infiltration dynamics at multiple scales (up to the scale of the entire pond) by measuring the ponding depth, sediment water content and groundwater levels, using pressure sensors, single-ring infiltrometers, soil sensors, and observation wells. During a month (January 2015) of continuous intensive MAR (2.45 × 106 m3 discharged to a 10.7 ha area), groundwater level has risen by 17 m attaining full connection with the pond, while average infiltration rates declined by almost 2 orders of magnitude (from ∼ 11 to ∼ 0.4 m d−1). This reduction can be explained solely by the lithology of the unsaturated zone that includes relatively low-permeability sediments. Clogging processes at the pond-surface – abundant in many MAR operations – are negated by the high-quality desalinated seawater (turbidity ∼ 0.2 NTU, total dissolved solids ∼ 120 mg L−1) or negligible compared to the low-permeability layers. Recharge during infiltration was estimated reasonably well by simple analytical models, whereas a numerical model was used for estimating groundwater recharge after the end of infiltration. It was found that a calibrated numerical model with a one-dimensional representative sediment profile is able to capture MAR dynamics, including temporal reduction of infiltration rates, drainage and groundwater recharge. Measured infiltration rates of an independent MAR event (January 2016) fitted well to those calculated by the calibrated numerical model, showing the model validity. The successful quantification methodologies of the temporal groundwater recharge are useful for MAR practitioners and can serve as an input for groundwater flow models.

Coupling distributed stormwater collection and managed aquifer recharge: Field application and implications

Groundwater is increasingly important for satisfying California's growing fresh water demand. Strategies like managed aquifer recharge (MAR) can improve groundwater supplies, mitigating the negative consequences of persistent groundwater overdraft. Distributed stormwater collection (DSC)–MAR projects collect and infiltrate excess hillslope runoff before it reaches a stream, focusing on 40–400 ha drainage areas (100–1000 ac). We present results from six years of DSC–MAR operation—including high resolution analyses of precipitation, runoff generation, infiltration, and sediment transport—and discuss their implications for regional resource management. This project generated significant water supply benefit over six years, including an extended regional drought, collecting and infiltrating 5.3 × 105 m3 (426 ac-ft). Runoff generation was highly sensitive to sub-daily storm frequency, duration, and intensity, and a single intense storm often accounted for a large fraction of annual runoff. Observed infiltration rates varied widely in space and time. The basin-average infiltration rate during storms was 1–3 m/d, with point-specific rates up to 8 m/d. Despite efforts to limit sediment load, 8.2 × 105 kg of fine-grained sediment accumulated in the infiltration basin over three years, likely reducing soil infiltration capacity. Periodic removal of accumulated material, better source control, and/or improved sediment detention could mitigate this effect in the future. Regional soil analyses can maximize DSC–MAR benefits by identifying high–infiltration capacity features and characterizing upland sediment sources. A regional network of DSC–MAR projects could increase groundwater supplies while contributing to improved groundwater quality, flood mitigation, and stakeholder engagement.