Aquifer Research Articles

Visualizing Electron Transfer through Silver Nanoparticle Formation and Photothermal Imaging: A Case Study of Nanoscale Zerovalent Iron.

Electron release and transfer are pivotal to the efficiency of multiple biogeochemical and pollutant processes. Despite substantial efforts to develop electron-transfer characterization techniques, in situ visualization of electron transfer remains challenging. This study introduces an innovative strategy for mapping electron-transfer distance using nanoscale zerovalent iron (nZVI) as a case study. In this method, silver ions (Ag+) are employed as electron traps, forming silver nanoparticles. These nanoparticles can then be immobilized in the agarose-solidified gel used as a heterogeneous porous medium to simulate the underground aquifer and visualized through photothermal imaging. In situ detection has unveiled remarkably extensive electron transfer, reaching distances of up to centimeters from the nZVI source. Nationwide groundwater investigations have further confirmed this long electron-transfer distance, ranging from 1.7 ± 0.4 to 9.6 ± 0.1 mm (agarose gel may not fully replicate the complex and heterogeneous conditions of groundwater environments). Importantly, the efficiency of electron transfer from nZVI was primarily influenced by factors such as nZVI dosage and groundwater matrix conditions, particularly the abundance of electron-shuttling materials like natural organic matter. Surprisingly, the inherent properties of nZVI had a lesser impact on electron-transfer distance. Our work highlights the long-distance electron transfer from nZVI, revealing a previously overlooked but ubiquitous nZVI remediation process.

Interdependence Between River Aquifer Groundwater Flow and Temperature–Depth Profiles: Type Curves Based on Pi Theorem and Numerical Simulations

Interdependence Between River Aquifer Groundwater Flow and Temperature–Depth Profiles: Type Curves Based on Pi Theorem and Numerical Simulations

Evaluating major element hydrogeochemistry and fluoride occurrence in groundwater of crystalline bedrock aquifers and associated controlling factors of Eumseong basin area, South Korea.

Long-term intake of high-fluoride water can cause fluorosis in bones and teeth or damage to organs. Fluoride in groundwater is primarily derived from reactions with rocks containing fluorine-related minerals, and fluoride concentrations are elevated in groundwater that has been reacting with these rocks for a long time. The purpose of this study is to investigate the origin and distribution of fluoride in groundwater and to assess the influence of various factors, including geology, on fluoride concentrations in groundwater. The Eumseong basin and surrounding areas were selected as the study area due to the diversity of geologic factors. 139 groundwater samples and 14 rock samples were collected, with groundwater samples subjected to field water quality measurements, chemical analysis, and statistical analysis, and rock samples subjected to microscopic observation and chemical analysis. Fluoride concentration in groundwater increased with well depth, and was highest in groundwater associated with granitic rocks rich in biotite. The fluoride concentration in groundwater showed a negative correlation with the distance to the fault, suggesting that deep groundwater may preferentially flow along fault zones in certain areas. In addition, high-fluoride groundwater had depleted water-stable isotope values, which is likely to be resulted from higher degree of water-rock interaction in groundwater recharged at higher elevations. Calcite precipitation in most groundwater appears to weaken fluorite solubility control on fluoride concentration. Multivariate statistical analysis revealed that water-rock interactions generally governed fluoride and major element concentrations, with high-fluoride groundwater clearly distinguished. These findings can aid in assessing fluoride occurrence in groundwater and managing water quality in areas with similar geological characteristics.

Regional hydro-climatic characterization for the efficient use and management of water Study case

Objective: To analyze official information to project future groundwater availability and demand scenarios, based on the different consumptive uses of the Alto Atoyac aquifer, in Tlaxcala, Mexico. Design/Methodology/Approach: The methodology used in this study included a bibliographic and documentary research. Likewise, based on the Penman-Monteith equation, quantitative research was used to calculate and estimate crop irrigation requirements. Results: The results of the availability and demand of groundwater showed a surplus of ≈23.34% in 2020. This percentage will gradually decrease in the following years until it reaches a 24.71% deficit by 2070. Consequently, a groundwater deficit in the Alto Atoyac aquifer will take place throughout the whole period (2020-2070). From 2040 to 2050, this deficit will gradually increase. Study Limitations/Implications: Measures for a sustainable use, exploitation, and conservation of the aquifer must be urgently implemented, as a regular and frequent measurements of aquifer depletion, through measures of phreatic and dynamic groundwater levels, also regular and frequent measures of groundwater extraction, water conduction through the conveyance and distribution system, and finally amounts of water applied to all crop pattern. Findings/Conclusions: The integration of the consulted and generated data allowed the development of groundwater availability and demand scenarios in the aquifer. In addition, comparisons between the said scenarios were established and conclusions were drawn. The growing water demand in the region —required to meet the basic needs of the localities and inhabitants and to keep driving the economic activities in the region— would have negative effects on the environment and the inhabitants, due to the overexploitation of the aquifer groundwater.

Perfluoroalkyl substances (PFASs) in groundwater and surface water in the Turin metropolitan area (Italy): An attempt to unravel potential point sources and compliance with environmental/drinking water quality standards.

The study investigated the contribution of five potential point source categories on the occurrence of 19 highly hazardous perfluoroalkyl substances (PFASs) in freshwater from the Turin metropolitan area (Italy) and assessed the quality of groundwater and surface water in compliance with European and Italian guidelines. PFASs were revealed in 29 and 24% of the investigated shallow (unconfined aquifers) and deep (semi- and confined aquifers) wells with a total concentration, as a sum (ΣPFASs), of 0.01-0.71 and 0.01-0.16μg/L, respectively. The PFAS occurrence in shallow groundwaters appeared more related to (potentially-) contaminated and reclaimed areas, landfills and waste management plants rather than plants subjected to integrated environmental authorisations and wastewater treatment plants. Overall, PFAS occurrences increased with the degree of industrialisation and urbanisation in both unconfined and (semi-) confined aquifers. PFASs were found in 96% of the sampling sites in streams with ΣPFASs values of 0.0002-0.47μg/L, whilst they do not occur in the investigated lake. A slight correlation was found between wastewater treatment plants and the occurrence of PFASs in streams. The annual ΣPFASs loads downstream of the Turin metropolitan Area were estimated around 150-220kg. Exceedances of the environmental and drinking water quality standards of Italy and Europe were frequently revealed.

Tracing nitrate contamination sources and dynamics in an unconfined alluvial aquifer system (Velika Gorica well field, Croatia).

Nitrate ions (NO3-) are one of the most common contaminants in the groundwater of the Zagreb alluvial aquifer, which hosts strategic groundwater reserves of the Republic of Croatia and supplies drinking water to one million inhabitants of the capital city. To better understand the origin and the dynamics of NO3- in the unsaturated and saturated zones, the stable isotopes of nitrogen (δ15N) and oxygen (δ18O) in dissolved nitrate, combined with physico-chemical, hydrogeochemical and water stable isotope data, were used in the current work, together with statistical tools and mixing models. The study involved monthly sampling of groundwater, surface water, precipitation and soil water samples. Additionally, the isotopic composition of total nitrogen (δ15Nbulk) was determined in solid samples representing the local nitrate sources. The combination of a nitrous oxide isotopic analyzer and the titanium(III) reduction method provides reliable measurements of δ15NNO3 and δ18ONO3, with optimal stability achieved under specific conditions. Nitrate in the study area predominantly originates from organic sources, with nitrification as the main biogeochemical process, while denitrification was identified at sampling sites under specific anaerobic conditions. Although statistical analysis can be a valuable tool, it should be applied with caution if NO3- originates from multiple sources. The isotopic composition of water showed that groundwater is predominantly recharged by the Sava River but its contribution varied spatially. The results also show the existence of a different recharge source in the southern part of the aquifer. Our findings highlighted the importance of employing a diverse range of analytical methods to obtain reliable and comprehensive understanding of nitrate contamination. By integrating multi-method approaches, stakeholders can better understand the complexities of groundwater contamination and implement more targeted measures to safeguard the water supplies for future generations.

On the flow behaviour of unconfined dual porosity aquifers with sloping base

The flow in an unconfined double-porosity aquifer with a sloping base is investigated and equations are developed for its description. In order to obtain a relatively simple description of the problem, similar assumptions as in Moutsopoulos (2021) have been adopted; the pressure in the unsaturated zone, especially in the fractures’ network, is considered to be atmospheric, and the Dupuit-Forchheimer approximation is invoked, reducing the dimensionality by eliminating the vertical direction. The derived equations have been linearized and solved analytically for a problem involving interaction between an inclined aquifer and an adjacent surface water body similar to the one examined by Akylas and Koussis (2007). The analytical solution has been checked against results obtained with state-of-the-art numerical codes. The agreement between the two approaches is excellent. The solution tools were used to gain insight in the influence of the aquifer's base inclination on the flow quantities.

Corrigendum to “Investigating Steady Unconfined Groundwater Flow using Physics Informed Neural Networks” [Advances in Water Resources Volume 177 (2023), 104445

Corrigendum to “Investigating Steady Unconfined Groundwater Flow using Physics Informed Neural Networks” [Advances in Water Resources Volume 177 (2023), 104445

Extensive Admixture Among Karst-Obligate Salamanders Reveals Evidence of Recent Divergence and Gene Exchange Through Aquifers.

Karst ecosystems often contain extraordinary biodiversity, but the complex underground aquifers of karst regions present challenges for assessing and conserving stygobiont diversity and investigating their evolutionary history. We examined the karst-obligate salamanders of the Eurycea neotenes species complex in the Edwards Plateau region of central Texas using population genomics data to address questions about population connectivity and the potential for gene exchange within the underlying aquifer system. The E. neotenes species complex has historically been divided into three nominal species, but their status, and spatial extent of species ranges, have remained uncertain. We discovered evidence of extensive admixture among species within the complex and with adjacent lineages. We observed relatively low levels of differentiation among all sampling localities which supports the hypothesis of recent divergence. Nominal taxonomy, aquifer region and geography each accounted for a modest amount of the overall population genomic variation; however, these predictors were largely confounded and difficult to disentangle. Importantly, current taxonomy of the three nominal species does not reflect the admixture apparent in clustering analyses. Inference of migration events revealed a complex pattern of gene exchange, suggesting that Eurycea salamanders have a dynamic history of dispersal through the aquifer system. These results highlight the need for greater understanding of how stygobiont populations are connected via dispersal and gene exchange through karst aquifers. These results also highlight the applicability of population genomics data as a powerful lever for investigating connectivity among populations in systems where direct detection of dispersal paths is difficult, as in underground, aquatic systems.

Application of Pumping Tests to Estimate Hydraulic Parameters of Volcanic Aquifers in Lake Tana Basin, Ethiopia

The purpose of this study was to enhance the understanding and sustainable groundwater management of volcanic aquifer systems by estimating key hydrogeological parameters. The transmissivity of a volcanic aquifer system was estimated using analytical solutions based on 68 constant rate and recovery data sets collected from various sources. A combination of hydro-lithostratigraphy and diagnostic plots was employed to identify the aquifer types and flow conditions, which facilitated model selection. Transmissivity of the confined aquifer was modeled using both Theis and Cooper–Jacob methods, with the Theis residual drawdown solution utilized for estimation. For the unconfined aquifer, the Neuman method was used, and the Hantush/Jacob method was employed for leaky aquifers. The results showed that the transmissivity of the Tertiary basalt varied from 0.38 m2/d to 860 m2/d, while the Quaternary aquifer system ranged from 2.33 m2/d to 1.8 × 104 m2/d, indicating an increase in transmissivity with younger volcanic flows. Specific capacity (SC) was estimated for 74 wells and the values ranged from 0.62 to 5860 m2/d. This wide variation of specific capacity and transmissivity showed significant heterogeneity within the volcanic aquifers. This study introduces the innovative application of derivative diagnostic plots in groundwater research, offering an efficient approach for analyzing and interpreting pumping test data to characterize aquifer systems in various hydrogeologic units. This study focuses on aquifer characterization in hard rock formation, demonstrating methods that can be applied to similar geological environments globally. For the Blue Nile basin in general and for the Lake Tana basin in particular, the study result of aquifer characterization will contribute to exploration, development, and improved groundwater management in the region.

Geoelectrical assessment of groundwater potential and aquifer characteristics in the west region of Cameroon

Geoelectrical assessment of groundwater potential and aquifer characteristics in the west region of Cameroon

The Utilisation of Solar-Powered Boreholes for Groundwater Supply: Addressing Water Scarcity in the Polokwane Municipality, Mankweng Cluster

In many African countries, including South Africa, groundwater remains vital for rural communities, yet sustainable methods of its supply still require improvement. The purpose of this study is to enhance groundwater supply through an innovative and sustainable borehole system that improves reliability and ensures a consistent water supply. This study was motivated by the need to provide sustainable water access in rural communities by addressing critical gaps in existing groundwater supply systems, thereby enhancing community resilience. This study identified a problem of water scarcity in the Polokwane Municipality, Mankweng Cluster, where the existing borehole systems are inadequate to supply groundwater. Handpumps demand significant physical effort, grid-powered boreholes cease to operate during frequent power cuts, and the inconsistent diesel supply further limits borehole operation. The study was conducted using a qualitative approach, involving data collection through interviews that were analysed using content analysis. Findings indicate several challenges, including power cuts, diesel supply shortages, poor infrastructure maintenance, vandalism, and theft of equipment, which affect the proper operation of boreholes. The study concludes that water scarcity in the Mankweng Cluster stems from inadequate water infrastructure. The study recommends implementing a solar-powered borehole system that uses photovoltaic energy to pump water from underground aquifers.

Analysis of shortcomings in the strategy and practice of water supply to the population, based on the war experience

The problems associated with the quantitative, qualitative, environmental, economic and other aspects of water resources, in particular the quality of drinking water, are of paramount importance today. The amount of water used is many times greater than other extractive resources. Water is the most important substance on our planet, primarily because it is necessary to sustain life. Providing the population with a sufficient amount of good quality drinking water is a strategic task for the national government.Drinking water used for centralised water supply to the population is drawn from surface water sources and groundwater aquifers. Historically, surface water has been preferred as the main source of water supply.The Dnipro River and its numerous tributaries are the main source of water supply for 75% of the Ukrainian population. However, due to significant technogenic pressures on the water quality in the Dnipro River and its catchment area the surface water is characterised as polluted and highly polluted in terms of chemical and bacterial contamination.In order to improve the quality component of the domestic drinking water supply to the population and industrial enterprises (mainly food production), particular attention should be paid to the increased use of groundwater. The experience gained during the war suggests the need to establish a local water supply system based on pumping stations (i.e., buvettes) with reserve water sources and means of delivering water to the consumption network.The article analyses the existing shortcomings and problems in the organisation of domestic drinking water supply in Ukraine and outlines some steps to improve the situation.

USE OF GEO-INFORMATION SYSTEMS FOR GROUNDWATER MONITORING

Abstract . The article is devoted to the study of the possibilities of using geographic information systems (GIS) for monitoring the state of groundwater, which is important for ensuring environmental safety and sustainable management of water resources. Groundwater is an important source of fresh water for the population, industry and agriculture, but it is vulnerable to various pollutions caused by both natural and anthropogenic factors. Therefore, the implementation of reliable monitoring systems that allow timely detection, assessment and forecasting of changes in water quality is necessary to prevent the deterioration of the ecological situation and prevent the spread of pollution. Geographic information systems (GIS ) offer significant opportunities for the collection and integration of large volumes of spatial data, including satellite images, remote sensing results, automated sensor data, and field observations. GIS allow creating multi-layered maps reflecting the ecological state of underground aquifers, modeling pollution processes and predicting their possible impact on nearby ecosystems and water sources. Thanks to the use of GIS, it is possible to combine data from different sources in a single interactive system, which simplifies analysis and provides the ability to quickly respond to any detected deviations. The article examines in detail the key methods used within GIS for groundwater monitoring, including satellite sounding to analyze changes in the earth's surface, spectral indices to assess the state of vegetation and soil salinity, and radar methods to determine soil electrical conductivity. Particular attention is paid to the application of three-dimensional modeling, which allows visualization of the spread of pollution in underground aquifers, which facilitates decision-making regarding the optimal location of monitoring stations and the design of protective structures. In combination with automated sensors recording water parameters in real time, GIS provides continuous monitoring of the physico-chemical indicators of groundwater and allows for prompt assessment of their condition. The article also analyzes the possibilities of using predictive modeling in GIS to assess the further spread of pollution and develop environmental risk management measures. It is described how mathematical models in GIS can help predict the impact of anthropogenic and natural factors on groundwater, which ensures the development of scientifically based solutions to reduce pollution and maintain water quality at a safe level. The implementation of GIS in groundwater monitoring is an important step towards increasing the efficiency of water resources management, ensuring their protection from pollution and preserving the ecological stability of the regions.

RESEARCH OF PROCESSES OF SORPTION OF COPPER IONS BETWEEN NATURAL CLAY MATERIALS FOR PROTECTION AGAINST POLLUTION OF UNDERGROUND AQUIFER HORIZONS

Experimental experiments with white clay from three deposits of Mykolaiv and red clay from Cherkasy region regarding sorption properties in relation to Cu2+ ions confirmed the ability to use local natural materials in the processes of cleaning from pollution in the water environment. A comparative analysis of red and white clay samples showed that red clay has a greater sorption capacity. The experiment was performed for two stages of filtration - drip and suspended, which take place during the operation of reclamation facilities and treatment facilities. For the stage of supported filtration, the experiments conducted by the authors showed a decrease in the sorption capacity of all samples, which was also confirmed by the calculations of Freundlich adsorption constants, which quantitatively characterized the adsorption process for each sample, as well as an increase in the averaged filtration coefficients at the stage of supported filtration.Experimental studies on the extraction of heavy metal ions using Cu2+ as an example were carried out according to the standard method using the colometric method with the diethyldithiocarbamate reagent under the condition of an initial concentration of Cu2+ in the solution of 5.8 mg/dm3.Результати проведеного експерименту свідчать, що при облаштуванні екранованих спо-руд глинистим екраном, крім протифільтраційних властивостей облицювання, що залежать від його товщини, отриманої щільності та інших параметрів після укладки, слід враховувати сорбційні властивості такого облицювання, режиму роботи споруди і, відповідно, величину гідравлічного на-пору.The results obtained during this experiment can also be used in the installation of anti-filtration screens of settling tanks and tailings of various kinds, as well as in the sanitation of water bodies in order to prevent pollution of the underground aquifer.

Physicochemical Qualities of Groundwater near Solid Waste Disposal Site in Aba, Abia State, Nigeria

Groundwater aquifer from solid waste dumpsites is probable of discharging toxic pollutant to groundwater which is unsafe to human health and local ecosystem. This study was conducted to examine the physicochemical qualities of groundwater around solid waste dumpsite in Aba, Abia State during wet and dry seasons. The physicochemical analysis of the groundwater samples was determined in accordance with the standards of the American Public Health Association (APHA). The results obtained from the groundwater samples were compared with World Health Organization (WHO) and the Nigerian Standard for Drinking Water Quality (NSDWQ) permissible limit of those studied parameters in drinking water. The physicochemical values obtained from the groundwater around the dumpsite in both season shows that some of the tested parameters existed in values higher than both WHO and NSDWQ standards for drinking water quality. The results also showed that the concentrations of cadmium, aluminum, iron and zinc were within the WHO and NSDWQ standard, whereas, the concentrations of chromium, copper and lead exceeded the WHO and NSDWQ standards for drinking water quality in both studied seasons. Findings from this study suggest that dumpsite solid waste could impact negatively on some physicochemical qualities of groundwater sited around their vicinity. Therefore, the location of solid waste dumpsites around residential areas should be discouraged.

MASTER RECESSION CURVE VISUALIZATION USING SEVEN BASEFLOW RECESSION MODELS IN PAIRED WATERSHEDS

River flow recession analysis plays a crucial role in understanding how watersheds release water during dry periods. Consequently, modeling baseflow recession is closely related to the characteristics of unconfined aquifers, storage behavior, and the discharge properties of the watershed. While several theories exist on modeling recession curves, limited research has compared different approaches regarding baseflow recession characteristics. This study aims to model seven baseflow recession equations in paired watersheds in Ambon City. The research methodology involves calibrating seven baseflow recession models using the Recession Curve (RC) 4.0 Hydro Office software. The tested models include Linear Reservoir, Exponential Reservoir, Double Exponential Horton, Dupuit-Boussinesq Aquifer Storage, Depression Storage, Turbulent Flow Model, and Hyperbolic Function Model. The calibration results yield optimal combinations of recession parameters. The parameterization order from highest to lowest is as follows: Depression Storage, followed by the Hyperbolic Function, Exponential Reservoir, Turbulent Flow Model, Double Exponential Horton, Linear Reservoir, and Dupuit-Boussinesq Aquifer Storage. Quantifying baseflow recession constants and coefficients is essential for understanding baseflow behavior. Visualizing the slope of the Recession Curve (MRC) reveals that models with high recession constants tend to have gradual MRCs, while low recession constants result in steep MRCs. The MRC slope further describes the relationship between storage conditions and discharge from the watershed. The advantage of creating MRCs from discontinuous recession segments lies in their ability to appropriately describe the MRC process and provide quantitative parameters relevant to drainage mechanisms. MRCs also serve as an optimal automated computational tool.

Hydrogeological and Hydrochemical Study of Groundwater Aquifer in Wasit Governorate - East of Iraq

The main aim of groundwater studies is to assess the physical and chemical characterizations of water-bearing layers as a goal for assessing their suitability for various purposes Wasit Governorate, which is located in eastern Iraq, is an important area in terms of agriculture and poultry and livestock husbandry. The area mainly depends on groundwater, especially on the Iraqi-Iranian border. The area was investigated (40) wells inventoried during the field study and used to demonstrate the hydrogeological and hydrochemical properties. The groundwater aquifer is composed of Quaternary deposits and Mukdadiyah formation. The mean thickness, transmissivity, and maximum yields were 53 meters, 114 m<sup>2</sup>/day, and 600 m<sup>3</sup>/day, respectively. The groundwater moved partially to the western parts and mainly towards the southern parts of the area towards Shuwaicha Marsh, which is located outside the study area. The salinity map showed a regular decrease in salinity concentrations towards the central and southwestern parts of the area due to groundwater recharge from infiltrated surface water. The groundwater is brackish to saline, with two dominant calcium and sodium sulphate types. The central area between Zurbatia and Badra towns can be a qualified location to increase well drilling due to salinity decreasing as the transmissivity and maximum yields increase.

The reconstruction of coastal carbonate sequence stratigraphy: A modern-systems approach

Sequence stratigraphy is the primary tool used by sedimentologists to predict bed-scale flow properties of both marine carbonate reservoirs (associated with carbon sequestration and hydrocarbon recovery) and groundwater aquifer systems. Coastal carbonate sequence stratigraphic models have been predicated upon the existence of parasequences, shallowing-upward successions bounded by marine flooding surfaces. Transgressive deposits in such models have been assumed to be mostly absent, whereas regressive deposits are presumed to form through the successive basinward stepping of shoals and their associated lagoons over open platforms. A review of modern coastal systems calls these assumptions into question. Transgressive deposits are substantive. In particular, in situ lagoonal and tidal-flat deposits left behind by overriding landward-migrating barriers are common across Holocene carbonate platforms. Furthermore, regressive deposits are not represented by prograding shoals and lagoons, but by lagoonal abandonment, and grainy shoreface progradation capped by strandplains, with overlying accommodation restricted to swales where only thin, discontinuous, intertidal mud flats form. We present a novel sequence-stratigraphic model based on these modern-systems observations with significant implications for subsurface geobody connectivity and fluid-flow prediction.

Comparing Recovery Volumes of Steady and Unsteady Injections into an Aquifer Storage and Recovery Well

Aquifer Storage and Recovery (ASR) can involve injecting available surface water into an unconfined aquifer and then extracting it to provide secondary water for irrigation. This study demonstrates a method for evaluating the appropriateness of steady injection versus unsteady injection for an assumed situation. In design, it can be important to affect the transient: the proportion of the injected water that would be subsequently extracted (versus that remaining in the aquifer) and the proportion within the extracted water that would be an injectate (versus ambient groundwater). These proportions can be predicted from the predicted value of an ASR well’s Recovery Effectiveness (REN)—the time-varying proportion of injectate that is extracted subsequently from the same fully penetrating well. Applying the demonstrated procedure with appropriately detailed data and simulation models can predict the REN values resulting from steady versus unsteady injection, followed by steady extraction. For convenience in displaying and computing REN, the injectate was assumed to have a 100 ppm conservative solute concentration. For this demonstration, a homogenous isotropic unconfined one-layer aquifer was assumed. The scenarios involved steady or unsteady injection for 61 days via a fully penetrating ASR well. Then, 91 days of steady pumping led to the extraction of a total volume equal to that injected. For the assumed hydrogeologic data—31 years of Salt Lake City, Utah, rainfall data and estimated captured runoff—the results show that steady injection is more likely to cause a predictable REN but might not cause a higher REN than daily varying injection of the same total volume. Assuming different runoff or hydrogeologic flows would lead to different REN values. Steady injection causes a predictable groundwater mound and can assure a sufficient vadose zone thickness for overlying plants. Augmentation and storage of captured rainwater can help to provide a steady injection rate. For a situation that requires REN management, appropriate simulations can help water managers design ASR systems that will achieve REN goals and increase sustainable groundwater availability.