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This study evaluates the vulnerability of aquifers to the nitrate concentration variations. Prediction of nitrate concentration using MT3DMs modeling for a period of 10 years. The results showed th...

As part of the Springer Nature Content Sharing Initiative, you can publicly share full-text access to a view-only version of your paper by using thefollowing SharedIt link: https://rdcu.be/cCd8u; International audience; The study of groundwater resources using pumping test data is usually carried out with the Theis solution, which enables the hydraulic parameters of porous aquifers such as the transmissivity and storage coefficient, to be estimated from the water-level drawdown. However, the data fitting can fail and provide only an indication that the pumped aquifer has a complex structure. Here, a diagnostic plot on log-derivative drawdown is used to identify flow regimes and thus aquifer heterogeneities, leading to plausible conceptual models. Nevertheless, the diagnostic plot is insufficient and must be accompanied by further modelling because of the nonuniqueness of the drawdown log-derivative signal. The proposed approach is applied to an alluvial plain in France, known to be complex because the deposition processes change over time, resulting in channel belts limited by low-permeability deposits in the floodplain or three-dimensional (3D) interconnected structures. Six analytical models were used to simulate drawdown and its derivatives during a three-day transient pumping test. The diagnostic performed on the pumping well showed that four conceptual models, with highly contrasted hydrodynamic behaviours, may correspond to the diagnostic. The joint use of pumping-well and observation-well data allowed the only appropriate model to be identified—a dual-permeability model characterizing a multilayer aquifer. The conceptual model matched the geological observations in boreholes and corroborates the fluvial sequence stratigraphy of the alluvial plain. The pumping test used here is a tool to explore the 3D architecture of the fluvial reservoir at the scale of the depositional sequence in the floodplain.; El estudio de los recursos hídricos subterráneos a partir de los datos de los ensayos de bombeo suele realizarse con la solución de Theis, que permite estimar los parámetros hidráulicos de los acuíferos porosos, como la transmisividad y el coeficiente de almacenamiento, a partir del descenso del nivel del agua. Sin embargo, el ajuste de los datos puede no funcionar y proporcionar sólo una indicación de que el acuífero bombeado tiene una estructura compleja. En este caso, se utiliza un diagrama de diagnóstico de la depresión logarítmica derivada para identificar los regímenes de flujo y, por tanto, las heterogeneidades del acuífero, lo que conduce a modelos conceptuales plausibles. Sin embargo, el diagrama de diagnóstico es insuficiente y debe ir acompañado de una modelización adicional debido a la no unicidad de la señal log-derivada de la depresión. El enfoque propuesto se aplica a una llanura aluvial en Francia, conocida por su complejidad debido a que los procesos de deposición cambian con el tiempo, dando lugar a franjas de canales limitadas por depósitos de baja permeabilidad en la llanura de inundación o a estructuras tridimensionales (3D) interconectadas. Se utilizaron seis modelos analíticos para simular la depresión y sus derivados durante un ensayo de bombeo transitorio de tres días. El diagnóstico realizado en el pozo de bombeo mostró que pueden corresponder cuatro modelos conceptuales, con comportamientos hidrodinámicos muy contrastados. La utilización conjunta de los datos del pozo de bombeo y del pozo de observación permitió identificar el único modelo apropiado: un modelo de doble permeabilidad que caracteriza un acuífero multicapa. El modelo conceptual coincidió con las observaciones geológicas en pozos de sondeo y corrobora la estratigrafía de la secuencia fluvial de la llanura aluvial. El ensayo de bombeo utilizado aquí es una herramienta para explorar la arquitectura 3D del depósito fluvial a escala de la secuencia deposicional en la llanura aluvial.; L’étude des ressources en eau souterraine à partir de données d’essais de pompage est généralement réalisée avec la solution de Theis, qui permet d’estimer les paramètres hydrauliques des aquifères poreux, tels que la transmissivité et le coefficient d’emmagasinement, à partir du rabattement du niveau d’eau. Cependant, l’ajustement des données peut échouer et fournir seulement une indication relative à la complexité de la structure de l’aquifère sollicité par pompage. Ici, un tracé de diagnostic de la dérivé du rabattement selon une échelle logarithmique est utilisé pour identifier les régimes d’écoulement et donc les hétérogénéités de l’aquifère, conduisant à des modèles conceptuels plausibles. Néanmoins, le diagnostic de puits est insuffisant et doit être accompagné d’une modélisation plus poussée en raison de la non-unicité du signal de la dérivée du rabattement selon une échelle logarithmique. L’approche proposée est appliquée à une plaine alluviale en France, connue pour être complexe car les processus de dépôt ont évolué au cours du temps, donnant lieu à des zones de chenaux limitées par des dépôts peu perméables dans la plaine d’inondation ou à des structures tridimensionnelles (3D) interconnectées. Six modèles analytiques ont été utilisés pour simuler le rabattement et ses dérivés pendant un essai de pompage transitoire de trois jours. Le diagnostic réalisé sur le puits de pompage a montré que quatre modèles conceptuels, aux comportements hydrodynamiques très contrastés, peuvent correspondre au diagnostic. L’utilisation conjointe des données des puits de pompage et des puits d’observation a permis d’identifier le seul modèle approprié - un modèle à double perméabilité caractérisant un aquifère multicouche. Le modèle conceptuel correspond aux observations géologiques dans les forages et corrobore la stratigraphie séquentielle fluviale de la plaine alluviale. L’essai de pompage utilisé ici est un outil permettant d’explorer l’architecture 3D du réservoir fluvial à l’échelle de la séquence de dépôt dans la plaine d’inondation.; O estudo dos recursos hídricos subterrâneos utilizando dados de teste de vazão é comumente resolvido por meio da equação de Theis, o que permite que os parâmetros hidráulicos dos aquíferos porosos, como a transmissividade e o coeficiente de armazenamento, possam ser estimados a partir do rebaixamento do nível d’água. Porém, o ajuste dos dados pode falhar, indicando apenas que o aquífero bombeado apresenta uma estrutura complexa. Aqui, um gráfico de diagnóstico da derivada logarítmica do rebaixamento é usado para identificar o regime de fluxo e, portanto, a heterogeneidade do aquífero, levando a modelos conceituais plausíveis. Ainda assim, o gráfico de diagnóstico é insuficiente e deve ser acompanhado de mais modelos, devido ao sinal não único da derivada logarítmica do rebaixamento. A abordagem proposta foi utilizada em uma planície aluvial na França, conhecida por ser complexa, pois os processos de deposição mudam com o tempo, o que resulta em um cinturão de canais limitados por depósitos de baixa permeabilidade na planície de inundação ou por estruturas tridimensionais (3D) interconectadas. Seis modelos analíticos foram utilizados para simular o rebaixamento, e suas funções derivadas, durante um teste de bombeamento transiente de 3 dias. O diagnóstico simulado para o poço de bombeamento mostrou que quatro modelos conceituais, cada um com comportamento hidrodinâmico contrastante, podem corresponder ao diagnóstico. A junção dos dados do poço de bombeamento e dos dados de poço de observação permitiu a identificação do único modelo apropriado – um modelo de permeabilidade dual caracterizando um aquífero multicamadas. O modelo conceitual coincide com as observações da geologia dos poços e corrobora com a sequência estratigráfica fluvial da planície aluvial. O teste de bombeamento utilizado é uma ferramenta para explorar a arquitetura 3D do reservatório fluvial na escala da sequência deposicional da planície de inundação.; 利用抽水试验数据研究地下水资源通常采用 Theis 解, 它可以根据水位降深估算多孔介质含水层的水力参数, 如传导系数和蓄水系数。然而, 数据拟合可能会失败, 并且只能表明抽水含水层具有复杂的结构。在这里, 对数导数降深的诊断图用于识别流态, 从而识别含水层的异质性, 由此可形成合理的概念模型。然而, 由于降深对数导数信号的非唯一性, 仅用诊断图是不够的, 必须再建模分析。所提出的方法应用于法国众所周知复杂的冲积平原, 由于沉积过程随时间变化, 导致河岸带受到漫滩中低渗透性沉积物或三维 (3D) 互连结构的影响。在为期三天的非稳定抽水测试期间, 六个解析解模型用于模拟降深及其导数。抽水井上进行的诊断表明, 具有高度异质的水动力行为的四个概念模型可能与诊断相符。抽水井和观测井数据的联合使用可确定唯一合适的模型, 即表征多层含水层的双渗透模型。概念模型与钻孔中的地质观察相匹配, 并证实了冲积平原的河流相地层。此处使用的抽水试验是在漫滩沉积相尺度上探索冲积相储层 3D 结构的工具。

Groundwater pumping can reduce streamflow by reducing groundwater discharge and/or inducing streamflow infiltration, which together are referred to as streamflow depletion. Recently, analytical depletion functions (ADFs) have been suggested as rapid and accurate tools for streamflow depletion assessment, but their performance has only been tested in a few hydrogeological settings. To evaluate whether they will be useful tools for other regions with contrasting stream network and hydrogeological characteristics, we compared ADFs to calibrated MODFLOW models in BX Creek and Peace Region with distinct hydrogeological settings (interior plateaus & highlands, and boreal plains, respectively) and spatial scales (165 km2 and 1952 km2, respectively) in British Columbia, Canada. Results showed that ADFs can accurately identify streams most affected by pumping for 100% and 83% of wells in the BX Creek and Peace Region, respectively, and had small prediction errors compared with MODFLOW. Specifically, the mean absolute error of predicted depletion ranged from 2% to 14% of the highest simulated pumping rate over the study period of 30 years, with improved accuracy during the pumping season. We also found contrasting responses of ADF performance to hydrostratigraphic properties such as hydraulic conductivity, aquifer thickness, streambed conductance, and well depth across two domains, indicating that different drivers control ADF accuracy in different hydrogeological settings. Therefore, we conclude that ADFs are useful tools for conjunctive water management, but a good understanding of local hydrogeological conditions is needed to address the potential uncertainty of ADFs for decision-making.

In this study Aeromagnetic, ground-based magnetic and satellite imagery data have been processed and analyzed to delineate surface and subsurface structures to clarify its impacts on groundwater flow direction, and to detect the thickness of groundwater aquifer’s (accumulation) in the study area. To achieve this target, an interpretation of satellite digital elevation data is processed to generate the main drainage pattern in the area to delineate the Watersheds basins and where the surface water can be accumulated. Moreover, Aeromagnetic data have been used to detect the sedimentary cover in the area, and to assess the thickness distribution of the Nubian aquifer to detect the most eligible aquifer with the largest thickness, consequently the largest amount of groundwater reserve. Also, the ground magnetic survey was conducted in Wadi El Amal to reassure the results obtained from the airborne data. Two main approach techniques were applied to the data. Firstly, the trend analysis applied to the first vertical derivative map to detect main trend analysis and faults. The second approach is to calculate the depth to the basement, which represents the base of the Nubian aquifer in the area under consideration. The final results of the main trend found as follow, the ENE-WSW, NW-SE, and NE-SW trend which found to be is the main trend. The water table in this area is about 100 m, the calculated depth to the basement in the deepest parts study area is ranging between −300 and −700 below ground surface. The integration between satellite techniques and geophysical tools can give us the whole picture of groundwater distribution and its recharge sources.

Mapping and monitoring saltwater intrusion are critical for the sustainable management of groundwater in coastal aquifers around the world. Increasingly, geophysical methods, such as electrical resistivity tomography (ERT), have been used to address these needs. We identify methods for the inversion of ERT data that would most accurately map the location and geometry of an intrusion wedge. This is accomplished using laboratory and synthetic experiments, with the classic representation of an intrusion wedge perpendicular to the coast. The laboratory experiments allow us to collect ERT data on a saltwater intrusion wedge in an environment in which we have supporting data that provided (1) the distribution of salinity within the tank with which to verify our inversion results, (2) the resistivity, porosity, and permeability of the porous medium, and (3) the transform between resistivity and salinity. The synthetic experiments allow exploration of issues of specific interest related to the presence of lithologic heterogeneity at a field site: the role of lithologic heterogeneity in introducing complexity into the resistivity-salinity relationship and the geometry of the saltwater intrusion wedge. We find that using a reference model with a good approximation of the wedge to inform the inversion greatly improves the ability of the resulting resistivity profile to map the wedge. Where there is no, or limited, lithologic heterogeneity, a parametric approach, which constrains the range of possible solutions by solving for a sharp interface between the saltwater and freshwater regions, is very effective at capturing the wedge location and geometry. Where there is lithologic heterogeneity, a hybrid between the parametric and informed inversion approaches is most effective, resolving the wedge with a high level of accuracy with little a priori information.

Deep mining is the current and future mining focus in the coalfield of North China. Therefore, it is necessary to establish a water inrush assessment method suitable for deep mining. The conventional water inrush coefficient ( T ) method is simple to use, but its accuracy is low when the mining depth is very small or large because it neglects the role of the aquifer water yield. The main purpose of this paper is to introduce a simple water inrush risk assessment method that is more applicable in deep mining than the T method. In this study, the hydrogeological characteristics in deep mining were studied and the role of the aquifer water yield in water inrush was analyzed. Afterwards, an improved T method considering the aquifer specific yield ( q ) was established. In the new method, the critical water inrush coefficient changes with changing q following a negative correlation. The parameter thresholds were determined based on systematic data analyses of 186 mining cases. The results of the statistical analysis show that the accuracy of the new method at different mining depths is higher than that of the T method.

There are sparse hydrogeological data and insufficient hydrogeological knowledge in many areas of the world reliant on groundwater. Nicaragua’s Pacific coast is one such region that is also experiencing water scarcity resulting from increasing demand on groundwater resources and climate change. The primary source of water in the region is the aquifer system associated with the Brito Formation, which is a marine sedimentary stratum of mostly sandstone that blankets 75 km of coastline in southwest Nicaragua. This study focused on the Tola municipality with the objective to advance a conceptual understanding of the hydrogeology and to support sustainable water development. Results demonstrate a heterogeneous aquifer system with regional flow characteristics and other factors that influence groundwater availability and water quality. Primary porosity is low, and secondary porosity is the primary mechanism of aquifer storage and is influenced by geological structure and diagenesis processes. Groundwater recharge is spatially and temporally heterogeneous and direct recharge is low. Infiltration of streamflow and runoff, especially early in the rainy season, is thought to be a large component of groundwater recharge. Climate, flow and recharge dynamics, and low storage capacity make the Brito Formation a sensitive resource and vulnerable to drought, increased abstraction, and climate change. This assessment provides data and insights useful for informing future studies and investments within the region and may be applicable in other Central American and Caribbean nations with coastal sandstone aquifers.

Natural springs containing volcanic and magmatic components occur in association with these activities. However, features of deeply originated fluids and solutes were less documented from fields, where active volcanic and magmatic activities are not distributed. To characterize the presence of deep components and identify their major pathways 28 groundwater samples (~ 1230 m deep) were collected from hot spring sites located at western coast of Kumamoto, southwestern Japan, where the typical subduction related magmatisms are absent. The samples were measured for dissolved ion concentrations and stable isotope ratios (δ2HH2O, δ18OH2O, δ13CDIC and δ34SSO4) that were compared with data of 33 water samples from vicinity surface systems. The groundwaters were classified into three types based on major hydrochemistry: high Cl− fluid, low concentration fluid, and high HCO3− fluid. Our data set suggests that the high Cl− fluid was formed by saline water mixing with aquifer waters of meteoric origin and subsequently evolved by reverse cation exchange. The low concentration fluid is identical to regional aquifer water of meteoric origin that was subjected to cation exchange. The high HCO3− fluid showed the highest HCO3− concentrations (~ 3,888 mg/l) with the highest δ13CDIC (up to − 1.9‰). Based on our carbon mixing model and observed δ2HH2O and δ18OH2O shifts, it is suggested that dissolved carbon of mantle origin and small fraction of fluids generated in deep crust were transported towards surface through structural weakness under open tectonic setting. These deeply derived components were then mixed with waters in the surface systems and diluted. Their impacts on surface hydrological systems were limited in space except few locations, where deeply connected pathways are anticipated along active structural deformations.

The identification of the hydrological processes taking place at coastal systems and the interaction between aquifers and the sea have been key features for many groundwater-related studies. However, the suitability of different boundary conditions for representing the hydrodynamic conditions along the coast in modelling applications is widely discussed today. In this study, a groundwater flow model is developed for a coastal multilayer semi-arid aquifer system (Lavrio, Greece), which in turn is used for the comparison between alternative boundary conditions that are considered relevant for representing the coast. The sensitivity analysis and parameter estimation of the model parameters were conducted using a statistical approach, and the results show that the head-dependent boundary condition can produce a more representative simulation of the coastal system hydrodynamics. The response of the karstic aquifer is also simulated satisfactorily, proving that the modelling code is also suitable for simulating karstic aquifers, at least at a large scale. Finally, the hydraulic interconnection between the different aquifer layers within the study area is clarified, as groundwater is primarily discharged from the karstic to the alluvial aquifer.

Low-to-medium temperature geothermal fluids in the granite regions of southeastern China are an important renewable energy resource, but they are also a source of contamination containing highly toxic elements such as fluoride and arsenic. This study analyzed the origin of the geothermal fluids in a regional-scale hydrogeological unit in the city of Xiamen, China, based on isotope and hydrochemical analyses. The Br/Cl ratios suggested that the inland geothermal fluid is merely recharged by rainwater from the mountain edge, while the coastal geothermal fluid is originally recharged by the seawater and later mixed with rain-derived groundwater. The geothermal water featured high SiO2 and detectable Zn concentrations. The former reflects the significant water–granite interaction along the flow path, and the latter indicates the active hydraulic connection between surface waters, shallow aquifers and deep geothermal fluids. High radon content was detected near the deep conductive fault adjacent to a geothermal well, demonstrating that the fault damage zone acts as a major conduit for upward transport of the deep geothermal fluid. As a result, the fault damage zones developed in the granite are necessary for the formation of geothermal water, which leads to the uneven distribution of geothermal water in the subsurface. High-temperature geothermal water can be found in those regions with fairly sparse fault damage zones. In contrast, in the region with high-density fault activities, the active communication between shallow cool water and deep geothermal fluids can decrease the water temperature.

Nitrate isotopic values are often used as a tool to identify sources of nitrate in order to effectively manage ground water quality. In this study, the concentrations of NO3−, NO2−, and NH4+ from 50 boreholes and shallow wells in the Singida and Manyoni Districts were analyzed during the dry and wet seasons, followed by identification of nitrate sources using the hydrochemical method (NO3−/Cl−) and stable isotope (δ15N and δ18O) techniques. Results showed that NO2− and NH4+ concentrations were very low in both seasons due to the nitrification process. The concentrations of NO3− ranged from 2.4 ppm to 929.6 ppm with mean values of 118.5 ppm ± 118.5 ppm , during the dry season and from 2.4 ppm to 1620.0 ppm with mean values of 171.6 ppm ± 312.3 ppm , during the wet season. The higher NO3− contamination observed in the wet season could be due to rainfall which accelerated the surface runoff that collects different materials from various settings into the ground water sources. Nitrate source identification through hydrochemical technique revealed that most nitrates originated from sewage effluents and/or organic wastes such as manure. Likewise, the mean values of δ15N-NO3− ( + 20.90 ‰ ± 5.17 ‰ and + 18.30 ‰ ± 6.33 ‰ ) and the mean values of δ18O-NO3−( + 13.86 ‰ ± 3.18 ‰ and + 13.69 ‰ ± 3.97 ‰ ) suggest that 80% of boreholes and 52% of shallow wells were dominated with nitrate from sewage effluents and/or manure as most ground water sources were situated in densely populated areas with congested and poorly constructed onsite sanitation facilities such as pit latrines and manure. Therefore, to reduce nitrate pollution in the study area, a central sewer must be constructed to treat the discharged wastes. Also, groundwater harvesting should consider the proper principles for groundwater harvesting recommended by the respective authority to minimize chances of contamination and hence prevention of health risk.

The purpose of the work is to carry out integrated isotope-geochemical studies of the mineral waters of the Belokurikha deposit. The methods of titrimetry, ion chromatography, inductively coupled plasma mass spectrometry (ICPMS) have been used in the laboratory investigation of the chemical composition of waters. The isotope composition of oxygen, hydrogen and carbon in dissolved carbon dioxide has been studied with the help of the Isotope Ratio Mass Spectrometer FinniganTM MAT 253 equipped with the attachments for sample preparation H/Device (to analyze the δD ratio) and GasBench II (to analyze δ18O and δ13СDIC ratios). There are two aquifers at the deposit. The first nonartesian aquifer comprises loose sediments of the Quaternary age. The second artesian aquifer includes the granites of the upper Paleozoic age with the different fracture degree: from monolith to loosened. Three groups of waters are distinguished on the basis of geochemical coefficients: fracture-vein waters bedded in weathered granites; groundwaters of the zone of rare earth mineralization and background composition; surface waters of the Belokurikha river. The isotope data on oxygen and hydrogen provide evidence that the production aquifers of the Belokurikha field are fed through the infiltration of meteoric waters, with the feeding shift to winter precipitation. The paper provides the first data of the integrated isotope-hydrogeochemical studies of nitric-siliceous low-radon thermal waters of the Belokurikha deposit. The composition of these waters is HCO3-SO4 Na and SO4-HCO3 Na with the total dissolved salts value ranging from 198 to 257 mg/dm3. The waters are characterized by alkaline pH of 8.6–9.6, silicon content ranging from 19.8 to 24.6 mg/dm3, and they are referred to the fracture-vein waters of the Upper Paleozoic granites. 222Rn activity is up to 359 Bq/dm3. The ratios of δD (from -126.9 to -102.7 ‰) and δ18O (from -17.5 to -14.2 ‰) in the studied waters indicate their atmospheric origin. The values of δ13СDIC vary from -9.7 to -25.6 ‰ and point to the biogenic origin of carbon.

Groundwater level observations due to the lack of synoptic water-level measurements are often available with irregular time intervals. The results lead to an inaccurate understanding of the parameters affecting groundwater level changes and their time delays. This paper presents a simple and low-cost approach to interpolate the irregular, periodic intervals of recorded groundwater level data for the Najafabad aquifer located in central Iran. Forty-six monitoring wells with an average of 20 years of data were used for this study. Piecewise cubic Hermite interpolating polynomial (PCHIP), cubic spline, linear, and nearest neighbor are the selected interpolation methods. Cross-validation with leave-one-out technique was also applied to evaluate the accuracy of the methods under three conditions, including low, average, and high groundwater level decline. The analysis proved that (1) PCHIP interpolation showed a high performance in all of the groundwater level decline conditions (0.22

The hydraulic conductivity of an unconfined carbonate aquifer at the uplifted atoll of Minami-Daito, Japan, was evaluated by a combination of cross-spectral analysis, analytical solution, and density-dependent groundwater modeling based on observed groundwater levels in 15 wells and at sea level. The island area was divided into 10 subregions based on island morphology and on inland propagation of ocean tides. The hydraulic conductivity was obtained for each subregion using analytical solutions based on phase lags of M2 constituents of ocean tides at each well by assuming two aquifer thicknesses (300 and 1,800 m) and two effective porosities (0.1 and 0.3). The density-dependent groundwater model evaluated the hydraulic conductivity of the subregions by reproducing observed groundwater levels. The hydraulic conductivity in the subregions was estimated as 3.46 × 10−3 to 6.35 × 10−2 m/s for aquifer thickness of 300 m and effective porosity of 0.1, and as 1.73 × 10−3 to 3.17 × 10−2 m/s for aquifer thickness of 1,800 m and the effective porosity of 0.3. It was higher in southern and northern areas, and higher in interior lowland than in the western and eastern areas. Fissures and dolomite distributions on the island control differences of the omnidirectional ocean tidal propagation and cause these differences in hydraulic conductivity. The method used for this study may also be applicable to other small islands that have few or no data for hydraulic conductivity.

This study focuses on the development of two GIS-based approaches that are used jointly to evaluate the groundwater resources associated with granular aquifers in shield environments. The first approach is a multi-criteria analysis (MCA) using an analytical hierarchic process (AHP) based on geological and hydrogeological data for ranking the probability of finding readily available groundwater resources in a specific territory. The second approach relies on GIS-based geometric calculations that were developed for evaluating the extent and volume of aquifers. The approaches are applied on a 100 × 100 m grid in a 185,000-km2 area corresponding to watersheds of the James Bay area in Quebec, Canada. The MCA-AHP approach revealed that the unconfined granular aquifers that present the highest aquifer potential (AP) are sparsely distributed and mostly associated with glaciofluvial formations such as the Harricana and Sakami moraines. The geometric calculations approach allowed for estimating that the total volume of groundwater stored in the unconfined granular aquifers reaches approximately 40 km3. When used jointly, the two approaches reveal that the shallow unconfined aquifers that require increased groundwater protection account for approximately 5% of the territory. In areas of confined granular aquifers, the highest APs are located in river valleys and lowlands. A sensitivity analysis conducted on the MCA-AHP approach revealed that the grid size does not significantly affect the results. Therefore, the approach was expanded northward, to a 490,000-km2 territory reaching the Ungava Bay area. The proposed method could be adapted and applied in other shield areas.

Monitoring the quantity and quality of groundwater is a non-separable part of the environmental information system. In this paper, we attempted to develop a new method for the flexible design of groundwater monitoring networks based on monitoring wells priority. In other words, this method could suggest a network commensurate with the budget. DRASTIC model was used to calculate the vulnerability of the aquifer, which layer weights were optimized using the Differential Evolution (DE) algorithm to find the maximum correlation between the vulnerable points and the points that had a high concentration of electrical conductivity (EC). So, the aquifer net recharge had the highest correlation, which was verified by comparing the recharge maps and EC. The 10-year analytical capture zones for wells were calculated by WhAEM2000 and Monte Carlo simulation was used to uncertainty analysis of each layer in DRASTIC method. In the first strategy, “Average of optimized DRASTIC”, and the second strategy, “Average plus standard deviation of optimized DRASTIC”, was the vulnerability threshold. Finally monitoring priority was calculated by counting vulnerable pixels enclosed by capture zones. As a result, a list of the wells with priority is calculated that a decision-maker can choose high priority wells, considering the budget allocated to the project.

Physically based distributed hydrological models that coupled surface and groundwater processes are the key tools for groundwater resources management. WASH123D is one of the models that integrate multimedia multi-processes to simulate flow in different components of the watershed system at various spatio-temporal scale for watershed planning, management and support decision-making activities. This review study on WASH123D discussed its applications, numerical challenges, issues and future needs. Total 68 research articles were acknowledged since 1998; approximately half of these studies were conducted in south Florida for rehabilitation and management of Floridian aquifer system while others were conducted in river basins of Taiwan for flood forecasting and inundation during typhoons. Most of the WASH123D calibration and validation results for river stage and groundwater level were under satisfactory to very good level based on statistical performance indicators. However, coupled 1D river/2D overland/3D groundwater simulations need high-performance computing resources. Moreover, the integration of WASH123D with other numerical models is the most practical approach for stable and reliable real-time inundation forecasting. Besides the model calibration, WASH123D application was also tested as a case study in sub-regional area of Kaohsiung City, Taiwan. The groundwater modeling with multiple pumping scenarios examined the changes in hydraulic drawdown with respect to pumping rate. The long-term pumping slowly increases the drawdown, but it stabilized at a certain level depending on pumping rate. Numerical groundwater modeling is an alternative tool that can best describe aquifer response to external stresses without the need for costly aquifer pumping tests.

The remediation of petroleum-contaminated soil and groundwater is a challenging task. The petroleum hydrocarbons have a long persistence in both the vadose zone and in the aquifer and potentially represent secondary and residual sources of contamination. This is particularly evident in the presence of residual free-phase. Pump-and-treat is the most common hydrocarbon decontamination strategy. Besides, it acts primarily on the water dissolved phase and reduces concentrations of contaminants to an asymptotic trend. This study presents a case of enhanced light non-aqueous phase liquid (LNAPL) remediation monitored using noninvasive techniques. A pilot-scale field experiment was conducted through the injection of reagents into the subsoil to stimulate the desorption and the oxidation of residual hydrocarbons. Geophysical and groundwater monitoring during pilot testing controlled the effectiveness of the intervention, both in terms of product diffusion capacity and in terms of effective reduction of pollutant concentrations. In particular, non-invasive monitoring of the reagent migration and its capability to reach the target areas is a major add-on to the remediation technique. Most of the organic contaminants were decomposed, mobilized, and subsequently removed using physical recovery techniques. A considerable mass of contaminant was recovered resulting in the reduction of concentrations in the intervention areas.

The city of Essaouira is located along the north-west coast of Morocco, where groundwater is the main source of drinking, domestic and agricultural water. In recent decades, the salinity of groundwater has increased, which is why geochemical techniques and environmental isotopes have been used to determine the main sources of groundwater recharge and salinization. The hydrochemical study shows that for the years 1995, 2007, 2016 and 2019, the chemical composition of groundwater in the study area consists of HCO3–Ca–Mg, Cl–Ca–Mg, SO4–Ca and Cl–Na chemical facies. The results show that from 1995 to 2019, electrical conductivity increased and that could be explained by a decrease in annual rainfall in relation to climate change and water–rock interaction processes. Geochemical and environmental isotope data show that the main geochemical mechanisms controlling the hydrochemical evolution of groundwater in the Cenomanian–Turonian aquifer are the water–rock interaction and the cation exchange process. The diagram of δ2H = 8 * δ18O + 10 shows that the isotopic contents are close or above to the Global Meteoric Water Line, which suggests that the aquifer is recharged by precipitation of Atlantic origin. In conclusion, groundwater withdrawal should be well controlled to prevent groundwater salinization and further intrusion of seawater due to the lack of annual groundwater recharge in the Essaouira region.

In the Lake Winnipeg Basin (LWB), at both basin and regional scales, there are currently gaps regarding the significance of groundwater as a mediator of nutrient and contaminant fluxes to Lake Winnipeg. During 2018, surface water and groundwater samples were collected from various locations across the largest sand and gravel aquifer (Assiniboine Delta Aquifer [ADA]; 3800 km2) in the LWB as well as from surface water courses flowing above this aquifer. The samples collected during spring and fall were analyzed for anions and cations as well as for a series of isotopic and geochemical tracers (e.g. water isotopes, carbon 14, artificial sweeteners, pesticides, etc.). The results reveal that groundwater and the small watercourses flowing above the ADA have a similar chemical composition, which is in contrast with the chemical composition of the main watercourse flowing above the aquifer (Assiniboine River [AR]). When corroborated with stream discharge measurements this indicates that groundwater plays a significant role at local scale in controlling both the flow and the chemical composition of the AR tributaries. Nitrate showed low to non-detectable concentrations in both groundwater and surface water. With respect to groundwater, this could be related to the reducing conditions in the deeper aquifer in conjunction with relatively large groundwater travel times of up to 2400 years.

The study aims at employing geo-electrically and hydrogeologically derived indices to assess the vulnerability in an alluvial environment of Obot Akara and Nsit Atai counties in the hinterland of Akwa Ibom State, Southern-eastern Nigeria. Vulnerability maps have been generated using seven indices: depth to groundwater (D); net groundwater recharge (R); aquifer media (A); soil media (S); topography (T); impact of vadose zone (I) and hydraulic conductivity acronymized as DRASTIC. The DRASTIC vulnerability index (V) was computed as the sum of the product of weights and ratings. The results indicate that, for Obot Akara site, about 20% of the aquifer is classified as medium vulnerability, about 40% is high vulnerability and very high vulnerability. . For Nsit Atai, about 60% of the aquifer is classified as medium vulnerability while 20% represents high and very high vulnerability respectively. The results of the vulnerability assessment shows that the DRASTIC quality category in percentage is contributory from the seven parameters and hence avoidable anthropogenic activities leading contamination of groundwater should be avoided while the vulnerability maps should be employed to avoid locating boreholes in areas with very high vulnerability. With appropriate software programmes, ground-based geophysical data, hydrogeological and environmental inputs, the vulnerability assessment has been made to cover both the present and future exploitable groundwater resources for the healthy and economic benefits of human existence.

The Edwards Aquifer (EA) in Central Texas provides water supply for over two million people and contains springs that are hydrologically and ecologically important to the region. The residence time of groundwater in the EA ranges from a few days to many thousands of years, since water in the aquifer is contained and transported within both matrix porosity and large conduits. In this study, stable isotopes of water from five springs are investigated for tracing the origin of water and hydrological processes in the EA system during 2017–2019. There is a quick response of the isotopic signals measured at these springs to changes in the isotopic compositions of precipitation. By utilizing an isotope mixing model, we have identified sources of water for these springs with a bi-modal distribution of groundwater supply in the EA: water supplied from deep groundwater with a longer residence time (an average of 67%) and supplemental epikarst interflow with a shorter residence time (an average of 33%). The evolution of hydrochemical water types from HCO3–Ca to HCO3·Cl–Ca·Mg along the EA flowpaths indicates that inputs from epikarst interflow are greater in springs within the artesian zone than the springs within the contributing zone. HIGHLIGHTS Stable isotope tracers were utilized to understand the origins of spring water and hydrological processes in the Edwards Aquifer.; There is a quick response for isotopic signals in spring water to changes in the isotopic compositions of precipitation.; There is elevated input from epikarst interflow for spring water balance in the artesian zone than the contributing zone.

Extensive change in land use, climate, and over-exploitation of groundwater has increased pressure on aquifers, especially in the case of crystalline rocks throughout the world. To support sustainability in groundwater management require proper understating of groundwater dynamics and recharge potential. GIS based studies have gained immense popularity in groundwater exploration in recent years because they are fast and provide recent information on the resource for future growth. Thus, the present study utilized a GIS-based Weighted Overlay Index (WOI) model to identify the potential recharge zones and to gain deep knowledge of groundwater dynamics. The in situ infiltration tests have been carried out, which is the key process in groundwater recharge and is neglected in many cases for WOI. In the WOI, ten thematic layers from the parameters influencing and involved in the recharge process are considered to identify potential recharge zones. The results suggested a significant underestimation of recharge potential without considering site-specific infiltration rates that one needs to be considered. The present WOI model considered in situ infiltration information and classified the entire area into four recharge zones, good, moderate, poor, and very poor. The final integrated map compared with the real-time field data like water level fluctuation and infiltration to analyse occurrence and quantification of recharge. The estimated average groundwater draft is 21.9 mcm, while annual renewable recharge is only 5.7 mcm that causing a continuous fall of the groundwater table. The study is useful in selecting regions with more focussed recharge studies and suggested the need of reducing groundwater demand by changing cropping patterns through a predictive decision support tool.

Background. In recent years, mitigation of groundwater contamination resulting from the limited availability of freshwater for domestic use has become an important issue. The presence of heavy metals in water could have adverse effects on both plant and animal life. Objectives. The main objective of the present study was to determine possible heavy metal contamination in groundwater around Al-Buraihi sewage station in Taiz, Yemen and to understand possible sources of contamination and their relationships with groundwater. Methods. Wastewater samples were collected from a wastewater stabilization pond from Al-Buraihi sewage station and borewell water samples were collected from the vicinity. The presence of heavy metals was quantified using inductively coupled plasma-optical emission spectrometry (ICP-OES). Pearson correlation test was performed to understand the relationship between wastewater and groundwater samples. Results. Physical variables including pH, electrical conductivity (EC), dissolved oxygen (DO) and temperature and elements such as silver (Ag), arsenic (As), aluminum (Al), barium (Ba), boron (B), cadmium (Cd), chromium (Cr), iron (Fe), molybdenum, nickel (Ni), selenium (Se) and zinc (Zn) exceeded the permissible limits recommended by international standards in wastewater samples. Conclusions. Treated sewage wastewater in the study area is not suitable for irrigation as the elements/heavy metals are accumulated in soil and plants and may be accumulated in humans and animals through bio-accumulation. In addition, these heavy metals reach the water table and aquifers through percolation, thereby polluting groundwater. Competing Interests. The authors declare no competing financial interests.

In this study, we present the efficiency of remediation scenario to attenuate the impact of acid mine drainage (AMD) contamination in the Kettara abandoned mine site. The study focuses on the AMD groundwater contamination of the Sarhlef shists aquifer. To predict the evolution of AMD groundwater contamination in the Kettara mine site under remediation scenario, a model of groundwater flow and AMD transport was performed.Piezometric heads were measured at the dry and wet periods from eleven wells located downstream of mine wastes. To elaborate a conceptual groundwater flow model, we faced with to the heterogeneity and anisotropy of fractured Sarhlef shists aquifer. Consequently, the study focused on the use of various approaches: 1. The inverse modeling by the CMA-ES algorithm is adopted as an alternative approach to determine hydraulic parameters indirectly, and 2. the model is treated as an equivalent porous media (EPM). The groundwater flow model was carried out in steady-state and transient conditions in the dry and wet periods using the PMWIN interface. The obtained results are satisfactory and show an excellent correlation between measured and computed heads. Contaminant transport model is used to solve the advection–dispersion equation and to generate the AMD concentration by MT3D via the PMWIN interface. A sensitivity analysis of the dispersivity coefficient is carried out. The AMD transport simulation was computed during periods of 1, 5 and 10 years, and the performed model indicates that the simulated concentrations under remediation scenario are reduced 1000 times comparing to the current concentrations. The study revealed a necessary approach in addressing an environmental issue for the AMD contamination. The results of the study will be a start-up for further research work in the study area and implementing it for the prevention of AMD propagation plume.

Newly, the Egyptian government initiated huge national projects for the reclamation and sustainable development of 1.5 million acres. Farafra Oasis is recognized as the focus of the first phase of this project where groundwater is the wellspring of the water for irrigation and drinking. Hence, exploration and assessment of groundwater aquifers are very essential in such area. A reconnaissance geophysical survey was conducted in the centre of Farafra oasis using Vertical Electric Sounding (VES), Transient electromagnetic (TEM), Audio-Magnetotelluric (AMT), Control-source Magnetotelluric (CSAMT), and Very Low Frequency (VLF) techniques for the investigation of shallow and deep groundwater reservoirs. In addition, geologic and stratigraphic information from the nearest well was utilized to confirm the geophysical outcomes. Integrated geophysical measurements succeeded to delineate the three zones A, B and C of the Nubian aquifer system in the investigated area. Also, several fault elements were delineated which control the influx and aggregating of the groundwater in both units; shallow and deeper one. Deeper aquifer (zone C) shows generally higher resistivity values, which consider the major aquifer of Nubian sandstone in the Western Desert of Egypt. Geochemical examinations of the groundwater sample show that the water is remarkable for all agriculture purposes (TDS = 95).

Prediction of groundwater flow fluctuations is considered an important step in understanding groundwater systems at this scale and facilitating sustainable groundwater management. The objective of this study is to determine the factors that influence and control groundwater flow fluctuations in a specific geomorphologic situation, by developing a forecasting model and examining its potential for predicting groundwater flow using limited data. Models for prediction of groundwater flow are developed based on artificial neural networks (ANNs). Neural networks with different numbers of hidden layer neurons were developed using climatic and geomorphological characteristics as input variables, giving predicted groundwater flow as the output. To evaluate enhanced performance models, several regression statistical parameters are compared. As an example, relative mean square error in groundwater flow prediction by ANN and correlation coefficient are 0.015 and 97%, respectively. The results of the study clearly show that ANNs can be used to predict groundwater flow in shallow aquifers of northern Algeria with reasonable accuracy even in the case of limited data. HIGHLIGHTS Combine hydrological and climatic data to estimate groundwater flows.; Test the performance of ANN's models to understand the behavior of groundwater.; Large-scale groundwater flow modeling for better management of water resources.; Proposal of a predictive model for a global vision of the distribution of groundwater.; Determining the order of importance of indicators that can influence groundwater flows.

In recent decades, changes in temperature, wind, and rainfall patterns of Southeast Asia induced by climate warming in the Tibetan Plateau result in many environmental changes that have serious impacts on the lower reach of the Mekong River basin, a region already battling severe water-related environmental problems such as pollution, saltwater intrusion, and intensified flooding. In the densely populated Mekong Delta located at the mouth of the Mekong River basin in southern Vietnam, the hydrogeological systems have been transformed from an almost undisturbed to a human-impacted state and saltwater intrusion into surface water and groundwater systems has grown to be a detrimental issue recently, seriously threatening freshwater supply and degrading the eco-environment. In this article, the impacts of human activities and climate change (e.g., groundwater over-exploitation, relative sea-level rise, storm surge, changing precipitation and temperature regimes, uncontrolled drainage canals, operation of hydropower dams, and rapid development of aquaculture) on saltwater intrusion into groundwater systems in the Mekong Delta are briefly reviewed. Based on current status of research findings regarding saltwater intrusion and the subsequent groundwater quality degradation under the impacts of human activities and climate change, major knowledge gaps and challenges are identified and discussed, including thickness and permeability of the silt and clay aquitard, present-day highly heterogeneous 3D distribution of saline groundwater zones, dynamic variation of saltwater/freshwater transition zone, and the most effective and economical control measure. To bridge these gaps, future work should: 1) apply environmental isotope techniques in combination with borehole tests to gain detailed hydrogeological information regarding spatial variation of permeability and thickness of the silt and clay aquitard; 2) intensify regular groundwater monitoring and collect as much groundwater samples from multiple hydro-stratigraphic units at different depths as possible to visualize the present-day highly heterogeneous 3D distribution of saline groundwater; 3) develop a series of variable-density coupled groundwater flow and salt transport models representing various scenarios of human activities and climate change for predicting future extent of saltwater intrusion; and 4) identify the dominant factor causing saltwater intrusion and determine the most effective and economical engineering technique to address saltwater intrusion problems in the Mekong Delta.

Acquiring sustainable water resources for water-based development of countries is the experts concern in this field, who seek to follow the clean development mechanism (CDM) regulations and overcome water crisis through integrated water resources management (IWRM). The Great Karun River basin is one of the major basins in the Middle East. This basin, containing six of the largest reservoir dams with a cumulative power plant capacity of more than 10,500 MW generates about 93% of hydropower of Iran. The water balance of the aquifer in the study area was simulated using MODFLOW model while water resources and surface water reserves were simulated by the water evaluation and planning (WEAP) model. A separate simulation was performed with each of two models and the results of two models were coupled using a link file. The multi-objective function optimization process including the maximized supply of demands and hydropower and the minimized aquifer drawdown was completed using non-dominated sorting genetic algorithm (NSGA-II). All effective system components, such as inter-basin water transfer, integrated use of water resources, variation of irrigation network efficiencies, and the effect of water shortage were studied and analyzed under the targeted scenarios. Finally, the best scenario, which was capable to supply the future needs until time horizon of 2040 was planned for the basin considering minimization of aquifer drawdown and optimal generation of hydropower resulting in a maximum decrease in emission of greenhouse gases.

Groundwater vulnerability assessment has become a crucial step in successfully protecting groundwater against pollution. An attempt of this study has been made to evaluate groundwater contamination risk using intrinsic vulnerability and land-uses in Vanathavillu, Kalpitiya and Katana area in Sri Lanka, using coupled DRASTIC with GIS as feasible methodology. The findings reveal that the groundwater in the areas under study falls under very low to high contamination risk. The higher risk of contamination has been identified in most of the Kalpitiya (about 82%) with the moderate along the beach in the west and next to Puttalam lagoon in the northeast and southeast. This is mainly due to pollution risk inherent with intense vegetable cultivation, over pumping, shallow groundwater tables and permeable sandy soil. Vanathavillu is under very low to moderate contamination risk, in which the moderate risk (about 13%) has especially been found the center, central southwest and west of the area. The relative less deep groundwater tables, possible seepage from the underlying limestone aquifer and less permeable red earth soil could be cause for the moderate risk in the area. Furthermore, results show that the Katana has low to moderately high groundwater contamination risk. Nitrate has a good agreement with the different pollution risk classes and that nitrate can be used as an indicator of aquifer degradation inherent with land-use activities in the coastal areas. Groundwater quality monitoring network should be set up to minimize the anthropogenic acts, particularly in high and moderate contamination risk zones.

Coastal reservoirs can alleviate freshwater shortages occurring in the nearshore zone. Deep pools patched at the bottom of reservoirs at greater depths than their adjacent beds maintain a high salinity and possibly provide preferential paths for saltwater backfill. However, such processes are not well understood. Laboratory experiments and numerical simulations were conducted to investigate the effect of the deep pool on subsurface flow and the salinization of coastal reservoir and adjacent aquifers. When seawater intruded into the initially fresh aquifer, the deep pool accelerated the uptake of saltwater to the reservoir from the salt wedge, forming a temporary salt plume around the pool. The saltwater plume also accelerated salt ingress and the evolution of the total salt mass in the coastal reservoir, resulting in the earlier attainment of a quasi-steady state (a classical saltwater wedge) than that when the deep pool was absent. Under steady-state conditions, the deep pool greatly enhanced the exchange of water across the reservoir-aquifer interface by 107% and raised the salinization level of the coastal reservoir by at least 10.3%. Sensitivity analysis suggested that a deeper pool and/or a pool located closer to the reservoir dam may enhance the water exchange and salinity level in the reservoir because it accelerates the water/salt inflow to the freshwater body to a greater extent. These findings may further contribute to improving the predictability and management of water quality in these coastal facilities.

Construction of managed aquifer recharge structures (MARS) to store floodwater is a common strategy for storing depleted groundwater resources in arid and semi-arid regions, as part of integrated water resources management (IWRM). MARS divert surface water to groundwater, but this can affect downstream fluvial processes. The impact of MARS on fluvial processes was investigated in this study by combining remote sensing techniques with hydro-sediment modeling for the case of the Kaboutar-Ali-Chay aquifer, northwestern Iran. The impact of MARS on groundwater dynamics was assessed, sedimentation across the MARS was modeled using a 2D hydrodynamic model, and morphological changes were quantified in the human-impacted alluvial fan using Landsat time series data and statistical methods. Changes were detected by comparing data for the periods before (1985–1996) and after (1997–2018) MARS construction. The results showed that the rate of groundwater depletion decreased from 2.14 m/yr before to 0.86 m/yr after MARS construction. Hydro-sediment modeling revealed that MARS ponds slowed water outflow, resulting in a severe decrease in sediment load which lead to a change from sediment deposition to sediment erosion in the alluvial fan. Morphometric analyses revealed decreasing alluvial fan area and indicated significant differences (p < 0.01) between pre- and post-impact periods for different morphometric parameters analyzed. The rate of change in area of the Kaboutar-Ali-Chay alluvial fan changed from −0.228 to −0.115 km²/year between pre- and post-impact periods.

Various studies have described upon importance of the performance of multilevel slug tests to assess hydraulic conductivity of aquifer sediment. For this study, slug tests were performed at 33 locations in 107 numbers of observation wells under six physiographic divisions in the Bengal Basin, Bangladesh. The objective of this paper is to evaluate the potential of multilevel slug tests to determine depth distribution and vertical variations of hydraulic conductivity in layered aquifer systems of the Bengal Basin that can be utilized for resource assessment. The studied aquifer sediments are dominated by unconsolidated fine and very fine sand with lenses of clay and silty clay aquitards. The hydraulic conductivity values commonly correspond with the lithology and their settlements. The unconsolidated sand in the Active and Tidal Delta contains high hydraulic conductivity values of up to 24.4 m/day. Older sediments in the Teppera Surface and Coastal Plain show lower average hydraulic conductivity. Very low hydraulic conductivities in few wells indicate the heterogeneities as well as poor development of these newly installed wells. Individual layers have relatively uniform grain size with well sorted sands, and their hydraulic conductivity values have a small variation, while sediments from multiple layers have variations in grain size with anisotropic signature and their hydraulic conductivity values, in many cases, vary by orders of magnitude. However, multilevel slug tests can provide considerable information about vertical variations in hydraulic conductivity under the right conditions. Although the slug tests were performed with precaution, unknown uncertainties in the well during the operation may influence the values of hydraulic conductivity. A more accurate values of the conductivity variations can be achieved by placing thin, low-conductivity layers in the sand pack that reduces vertical flow. Selection of drilling procedure and the techniques of measurement and analysis are also important to get good results. Factors like leakage and partial penetration should also be minimal for optimum results

Karst aquifers have distinct characteristics that make them complex compared to non-karstic aquifers. The complexity increases in coastal areas, due to the complicated mixing dynamics between groundwater and seawater. The combined use of hydrochemical and isotopic data is proved to be a useful tool to better understand the circulation of groundwater at coastal karst aquifer in southwest Turkey. The "Azmak Streamflow Karst System" is composed of about 150 spring outlets whose electrical conductivity values range between 1300 and 15,000 mu S/cm on the coast of the Aegean Sea. The total average flow is about 11 m(3)/s and the average total dissolved solids at the complete mixing point is about 3000 mg/l. This slightly brackish water is regarded to be strategic owing to its possible availability for future use. Major ions and stable isotope analyses as well as in situ measurements of physical parameters were carried out during a period of 2 years and evaluated to better understand the hydrogeological setting. Spatial and temporal variations of hydrochemical and isotopic constituents of sampled waters also provided a significant tool to elucidate the salinization mechanism in the study area. The results revealed that the Azmak streamflow-opposed to the common assumption-is the outflow of a multi-component hydrogeological system whose components are karst aquifer, alluvial aquifer, alluvial fan, seawater, and surface runoff. In addition, the results showed that sources other than seawater mixing contribute to the salinization of groundwater in the system.

Karst aquifers in subtropical regions are characterized by high variability of water availability and quality due to changes associated with rainy and dry seasons. An additional challenge for water management is the combination of surface-water and karst groundwater systems since high spatiotemporal dynamics cause high variability of water quality. In these cases, adapted protection strategies are required. In this study, a protection approach for the catchment of a river-water diversion point in a rural area in northern Vietnam is developed. The variability of water quality was evaluated by rainy and dry season synoptic surveys of suspended particles and microbial contamination at 49 sites and time series at three sets of paired sites under constant hydraulic conditions. The anthropogenic land-use activities in the catchment were mapped to identify potential contamination sources and to highlight the challenging combination of surface-water and karst groundwater management. The analyzed data indicate differences in water quality between the dry and rainy seasons and a higher influence on water quality from land use than from hydrologic conditions. Furthermore, the results suggest a high risk of contamination resulting from residential areas, agriculture, and livestock farming, and reveal the necessity of implementation of appropriate measures such as restricted farming and the hook-up of buildings to municipal sewage disposal. Finally, the data show that water quality can be improved by adjusting water withdrawals by the time of day. The applied methods can be transferred to other surface-water and karst groundwater systems in similar subtropical environments.

Here we present results of digital modelling of a specific setting of hypogenic carbonic acid speleogenesis (CAS). We study an unconfined aquifer where meteoric water seeps through the vadose zone and becomes saturated with respect to calcite when it arrives at the water table. From below, deep-seated water with high p CO 2 and saturated with respect to calcite invades the limestone formation by forced flow. Two flow domains arise that host exclusively water from the meteoric or deep-seated source. They are separated by a water divide. There by dispersion of flow, a fringe of mixing arises and widening of the fractures is caused by mixing corrosion (MC). The evolution of the cave system is determined by its early state. At sites with high rates of fracture widening, regions of higher hydraulic conductivity are created. They attract flow and support one-by-one mixing with maximal dissolution rates. Therefore, the early evolution is determined by karstification originating close to the input of the upwelling water and at the output at a seepage face. In between these regions, a wide fringe of moderate dissolution is present. In the later stage of evolution, this region is divided by constrictions that originate from statistical variations of fracture aperture widths that favour high dissolution rates and focus flow into this region. This MC-fringe instability is an intrinsic property of cave evolution and is present in all scenarios studied. We have investigated the influence of defined regions with higher fracture aperture widths. These determine the cave patterns and suppress MC-fringe instabilities. We have discussed the influence of the ratio of upwelling water flux rates on the rates of meteoric water. This ratio specifies the position of the mixing fringe and consequently that of the cave system. In a further step, we have explored the influence of time-dependent meteoric recharge. Furthermore, we have modelled scenarios where waters are undersaturated with respect to calcite. These findings give important insight into mechanisms of CAS in a special setting of unconfined aquifers. They also have implications for the understanding of corresponding sulfuric acid speleogenesis (SAS).

Nitrate contamination of subsurface aquifers is an ongoing environmental challenge due to nitrogen (N) leaching from intensive N fertilization and management on agricultural fields. The distribution and fate of nitrate in aquifers are primarily governed by geological, hydrological and geochemical conditions of the subsurface. Therefore, we propose a novel approach to modeling both geology and redox architectures simultaneously in high-resolution 3D (25m×25m×2m) using multiple-point geostatistical (MPS) simulation. Data consist of (1) mainly resistivities of the subsurface mapped with towed transient electromagnetic measurements (tTEM), (2) lithologies from borehole observations, (3) redox conditions from colors reported in borehole observations, and (4) chemistry analyses from water samples. Based on the collected data and supplementary surface geology maps and digital elevation models, the simulation domain was subdivided into geological elements with similar geological traits and depositional histories. The conceptual understandings of the geological and redox architectures of the study system were introduced to the simulation as training images for each geological element. On the basis of these training images and conditioning data, independent realizations were jointly simulated of geology and redox inside each geological element and stitched together into a larger model. The joint simulation of geological and redox architectures, which is one of the strengths of MPS compared to other geostatistical methods, ensures that the two architectures in general show coherent patterns. Despite the inherent subjectivity of interpretations of the training images and geological element boundaries, they enable an easy and intuitive incorporation of qualitative knowledge of geology and geochemistry in quantitative simulations of the subsurface architectures. Altogether, we conclude that our approach effectively simulates the consistent geological and redox architectures of the subsurface that can be used for hydrological modeling with nitrogen (N) transport, which may lead to a better understanding of N fate in the subsurface and to future more targeted regulation of agriculture.

Groundwater is the largest available reservoir of freshwater. But the rapid increase in the population and urbanisation, has led to over exploitation of groundwater which imposed tremendous pressure on global groundwater resources. Because of the hidden and dynamic nature of groundwater, it requires appropriate quantification for the formulation of groundwater planning and management strategies. The present study evaluates the efficacy of geospatial technology based Multi Influence Factor (MIF), Weight of Evidence (WofE) and Frequency Ratio (FR) technique to evaluate groundwater potential using a case study of basaltic terrain. The thematic layers influencing the groundwater occurrence viz. rainfall, slope, geomorphology, soil type, land use, drainage density, lineament density, and elevation were prepared using satellite images, hydrologic, hydrogeologic and relevant field data. Based on the conceptual frameworks of MIF, WofE and FR techniques these thematic layers and their features were assigned with appropriate weight and then integrated in the ArcGIS platform for the generation of aggregated raster layer which portray the groundwater potential zones. The results of validation showed that the groundwater potential delineated using MIF technique has a prediction accuracy of 81.94%, followed by WofE technique (76.19%) and FR techniques (71.43%). It is concluded that for evaluation of groundwater potential, the MIF technique is most reliable, followed by the WofE technique. The evaluated groundwater potential zones are useful as a scientific guide to identify the suitable location of wells and recharge structure in a cost-efficient way and also for the development of structured and pragmatic groundwater management strategies.

Due to the different in-situ stress level, mining stress state, and surrounding rock properties of steeply inclined deep coal mining, the mutation mechanism of underground engineering rock mass is complex. This paper studies the cause and control of mining disaster of steeply inclined deep coal resources in Wudong coal mine. The results show that the structural field is the key of multifield analysis, and particularly a large area of suspended roof is easy to expand energy and induce dynamic hazards. By means of borehole television- (BT-) transient electromagnetic (TEM) detection, it is found that there are hidden dangers of roof safety and suspected water hazards in Wudong coal mine, and the roof above the detection area (+575 m south roadway to 2250–2600 m) is in a suspended state; there is a suspected water-rich area in the range of 2320–2340 m and 2390–2400 m, and the lowest vertical height is +613.8–+615.5 m. Exploring and releasing the water in the aquifer effectively reduced the water pressure; in +575 m south roadway, +587 m measure roadway, and blasting chamber, the suspended roof blasting holes are constructed. Microseism- (MS-) TEM monitoring shows that the apparent resistivity fluctuates significantly, the microseismic energy and events have been significantly reduced, and it is maintained at a low level for two consecutive weeks, confirming the effectiveness of the stable release of the high-stress roof in the +575 m near stope area; at the same time, the safeguard measures for long-term roof dynamic monitoring are constructed.

The determination of changes in hydrogeological properties (e.g., permeability and specific storage) of aquifers disturbed by mining activity is significant to groundwater resource and ecological environment protection in coal mine areas. However, such parameters are difficult to continuously measure in situ using conventional hydrogeological methods, and their temporal changes associated with coal mining are not well understood. The response of well water level to Earth tides provides a unique probe to determine the in situ hydrogeological parameters and their variations. In this study, the tidal responses of well water level were employed to characterize the changes in hydrogeological parameters of the overburden aquifer induced by longwall mining in a coalfield, northwest China. Based on the long-term hourly recorded water level data, two analytical models were used to determine the temporal changes of permeability and specific storage of the overburden aquifer. The results showed that the hydrogeological parameters changed with the longwall coal face advance. When the longwall coal face approached the wells, the aquifer permeability increased several to dozens of times, and the response distance ranged from 80 m to 300 m. The specific storage decreased before the coal face reached wells and recovered after the coal face passed. The results of this study indicate that the hydrogeological parameter changes induced by coal mining are related to the location of the well relative to the coal face and the stress distribution in the overburden aquifer. This study revealed the changes in permeability and specific storage associated with the mining disturbance which could have great significance for quantitative assessment of the impact of mining on overburden aquifer.

Northern part of Lombok island has a unique geological phenomenon of submarine groundwater discharge. Submarine groundwater discharge needs to be conserved for its sustainability. This study asseses groundwater vulnerability for SGD conservation in the northern part of Lombok Island Indonesia. The assessment was conducted using aquifer vulnerability index methods. Vulnerability index value in the study area is high vulnerability index. This vulnerability index is getting higher toward the coast. The layer is tuffaceous pumice layer with a hydraulic conductivity value of 5 m/day. This layer makes the aquifer in the study area very vulnerable to contamination, especially for pollution involving vertical percolation and infiltration. Protective management is needed to prevent groundwater hazard in the research location due to groundwater pollution and heavy pumping. Anthropogenic activity at the study area should be anticipated because of the high index of aquifer susceptibility at the study area.

International audience; Fluid–mineral and fluid–rock interfaces are key parameters controlling the reactivity and fate of fluids in reservoir rocks and aquifers. The interface dynamics through space and time results from complex processes involving a tight coupling between chemical reactions and transport of species as well as a strong dependence on the physical, chemical, mineralogical and structural properties of the reacting solid phases. In this article, we review the recent advances in pore-scale imaging and reactive flow modelling applied to interface dynamics. Digital rocks derived from time-lapse X-ray micro-tomography imaging gives unprecedented opportunity to track the interface evolution during reactive flow experiments in porous or fractured media, and evaluate locally mineral reactivity. The recent improvements in pore-scale reactive transport modelling allow for a fine description of flow and transport that integrates moving fluid–mineral interfaces inherent to chemical reactions. Combined with three-dimensional digital images, pore-scale reactive transport modelling complements and augments laboratory experiments. The most advanced multi-scale models integrate sub-voxel porosity and processes which relate to imaging instrument resolution and improve upscaling possibilities. Two example applications based on the solver porousMedia4Foam illustrate the dynamics of the interface for different transport regimes (i.e., diffusive- to advective-dominant) and rock matrix properties (i.e., permeable vs. impermeable, and homogeneous vs. polymineralic). These parameters affect both the interface roughness and its geometry evolution, from sharp front to smeared (i.e., diffuse) interface. The paper concludes by discussing the challenges associated with precipitation processes in porous media, rock texture and composition (i.e., physical and mineralogical heterogeneity), and upscaling to larger scales.

The effect of waste dumps on groundwater quality on perched aquifers in Nsukka and environs was investigated by applying multivariate statistical analyses using Statgraphics Centurion XVII, ArcGIS ...

Septic systems located near coastal waterways can contribute to nutrients that lead to eutrophication, harmful algal blooms, and high levels of fecal coliforms such as E. coli. This study defines pathways and timescales of nitrogen transport released from septic systems using a groundwater-flow and nitrogen transport model of a coastal subdivision connected to 2,000 septic systems and dissected by a dense network of canals. Lift station effluent data are used as a proxy to quantify average household septic nitrogen and fluid contributions of 11 kg/year and 160 m3/year, respectively. These fluxes are upscaled and applied to five sewer conversion zones, each having a known number of septic systems. Model results provide a basis for assessing nitrogen transport timescales associated with (1) coastal groundwaters for regions with high septic density near the coastline and (2) groundwater–canal interaction. Timescales associated with nitrogen removal by natural groundwater flow in a sandy surficial aquifer, following septic to sewer conversion, are predicted by the model to be on the order of 2–3 years for 50% reduction and 8–10 years for 90% reduction. Both numerical and collected field data indicate that canals significantly influence groundwater flow and have the potential to convey nitrogen to coastal waters at rates several orders of magnitude higher than introduced by submarine discharge along the coast. Pre and post sewer conversion data on nitrate and total nitrogen in shallow groundwater from a nearby field site, obtained post-model development, support the nitrogen concentrations and timescales predicted by the numerical model.

This paper aims to propose a methodology to evaluate and quantify perturbed groundwater budgets considering the projected reduction of Average Snow Fraction of Surface Runoff (ASFSR). Future groundwater budgets are generated considering different CC temporal Scenarios, RCMs, as well as the status of each Groundwater Body (GwB). The proposed methodology is applied to the Central Mountain Range of Iberian Peninsula (Avila Province). Existing studies show a drastic Reduction on Snow Melting (RSM) and on Cumulative Snow Volume (CSV). This leads to a huge reduction of Average Snow Fraction of Surface Runoff (ASFSR) and on groundwater availability calculated through the indicator Perturbed Exploitation Index (PEI). There are important differences depending on the RCM used, on the temporal CC Scenario and on the GwB considered. Main difficulties and challenges comprise the lack of field data and rigorous studies on modelling of groundwater hydrodynamic modelling. Despite of that, research results show a robust and generalized increase in all Exploitation Indexes (EI). EI increase is of 4.17 % for IP1 (Short Term) RCP 4.5, 14.94 % for IP2 (Medium Term) RCP 4.5, 17.65 % for IP3 (Long Term) RCP 4.5. On the other hand, there is an increase of 9.89 % for IP1 RCP 8.5, 19.05 % for IP2 RCP 8.5 and 35.14 % for IP3 RCP 8.5. Thus, there is a generalised and very important decrease of recharge (PARR) of 59.03 % for IP1 RCP 4.5, 88.97 % for IP2 RCP 4.5, 90.02 % for IP3. Likewise, for RCP 8.5, there is a decrease of 72.69 % for IP1 RCP 8.5, 88.97 % for IP2 RCP 8.5 and 97.90 % for IP3.

The United Nations (UN) annual report on water resources released in 2015 announced that the world will face a global water deficit of about 40% by the year 2030. Around half of the world’s population depends on groundwater for fulfilling the daily consumption (drinking; domestic use). As humans require a water supply for their survival, it seems important to establish an adequate strategy for water resources management and for predicting the water balance which in their turn enable the estimation of groundwater recharge. Such a task has been the focus of the present study. This study intends to estimate the average recharge and predict the water situation under different scenarios up to 2050 for the Northern Gafsa aquifer (South-Western Tunisia), characterized by an arid climate. The estimation of the recharge rate and water balance depends on the piezometric data (recorded by 16 piezometers during 18 years (2001–2018)) which was used in the balance sheet method and in the interpolation by Arcgis software. The spatial study of the piezometric variation during the period between 2011 and 2018 has revealed that the southern part of the aquifer is the most vulnerable to depletion. The prediction of the water situation of the studied aquifer is established on three scenarios, corresponding to exploitation growth rates of 2.2, 4.8 and 8.5% for scenarios 1, 2 and 3, respectively. The average recharge rate in the Northern Gafsa aquifer was estimated of 25.6 mm/year. Simulations of the examined aquifer depict a negative water balance and a continuous drawdown. The 8.5% growth rate (Scenario 3) is expected to cause the total depletion of Northern Gafsa groundwater in 2045. Indeed, this serious situation requires the establishment of an adequate strategy to mitigate the current overexploitation (limiting illicit drilling…) and to satisfy the growth in water needs (finding other water resources…).

Evolving optimal management strategies are essential for the sustainable development of water resources. A coupled simulation-optimization model that links the simulation and optimization models internally through a response matrix approach is developed for the conjunctive use of groundwater and surface water in meeting irrigation water demand and municipal water supply, while ensuring groundwater sustainability and maintaining environmental flow in river. It incorporates the stream-aquifer interactions, and the aquifer response matrix is generated from a numerical groundwater model. The optimization model is solved by using MATLAB. The developed model has been applied to the Hormat-Golina valley alluvial stream-aquifer system, Ethiopia, and the optimal pumping schedules were obtained for the existing 43 wells under two different scenarios representing with and without restrictions on stream flow depletion, and satisfying the physical, operational and managerial constraints arising due to hydrological configuration, sustainability and ecological services. The study reveals that the total annual optimal pumping is reduced by 19.75 % due to restrictions on stream flow depletion. It is observed that the groundwater pumping from the aquifer has a significant effect on the stream flow depletion and the optimal conjunctive water use plays a great role in preventing groundwater depletion caused by the extensive pumping for various purposes. The groundwater contribution in optimal conjunctive water use is very high having a value of 92 % because of limited capacity of canal. The findings would be useful to the planners and decision makers for ensuring long-term water sustainability.

Quantification of the amount of the exchanged water between the surface water and a confined aquifer is a basic step in water balance and environmental hydraulics. The hydraulic connection between a surface water and a confined aquifer may occur through different recharge variations. The current research presents new analytical solutions for confined aquifer response to recharge variations and different inflow distributions. Different cases were studied, where a constant piezometric head is applied at the right boundary of the 2D confined aquifer plane and various distributions of water inflow through the recharging windows are considered on a part and/or parts of the left boundary. Finally, a uniform water inflow distribution on parts of the left boundary and a uniform distribution of water outflow at the right boundary was considered. Both steady and unsteady state problems can be solved using proposed equations. The performance of developed analytical solutions was examined compared to the numerical finite difference modeling. The results show reasonable precision of the developed analytical solutions. The developed solutions can be used as a benchmark to verify numerical approaches with similar boundary conditions.

Excessive sand mining to meet the growing demands of the construction industry has resulted in the degradation of rivers, lowering of groundwater table, saltwater intrusion into coastal aquifers, a...

Groundwater depletion poses a major threat to global groundwater resources with increasing trends due to natural and anthropogenic activities. This study presents a surface-groundwater framework for water resources modelling of ill-posed problems in hydrogeologically data-scarce areas. The proposed framework is based on the application of a conceptual water balance model and composed of surface hydrological (UTHBAL) and groundwater flow simulation with the integration of a Newton formulation of the MODFLOW-2005 code (MODFLOW-NWT) and PEST suite modules. The groundwater simulation includes a preprocessor tool for automated calibration and a post-processor tool for automated validation. The methodology was applied to a rural region of Central Greece, Lake Karla Basin, which is degraded due to groundwater resources overexploitation to cover irrigation water demands. The aquifer is modelled focusing on a precise simulation–validation procedure of the conceptual model. The groundwater model was calibrated with the calibration preprocessor tool for spatially distributed hydraulic conductivity with the pilot points method. The calibration process achieved satisfactory results as validated by the post-process analysis of observed and simulated water levels. The findings for the groundwater budget indicate that the groundwater system is still under intense pressure even though farming activity in recent years has turned to less water-intensive crops. HIGHLIGHT My research deals with the pilot points method on groundwater modelling in an area with scarce hydrogeologic data.