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With the gradual improvement in coal mining efficiency, the disturbance of groundwater systems caused by high-intensity mining also increases, leading to challenges in maintaining mine safety and protecting water resources in mining areas. How to accurately describe the dynamic changes in the groundwater system under mining and quantitatively predict mine water inflow are currently major problems to be addressed. Based on a full analysis of the response characteristics of a groundwater system to the extraction disturbance, this paper presents a new method to establish a mine hydrogeological conceptual model that can accurately represent the water inrush process. The unstructured-grid package of MODFLOW is used to accurately characterize the formation structure and finally make accurate water inflow predictions. Taking the Caojiatan coal mine in Shaanxi Province, China, as an example, a numerical model of unstructured water inflow is established, and the changes in the water inflow source and intensity are quantitatively evaluated. Compared with the traditional water inflow prediction method, the prediction accuracy of the new model is improved by 12–17%, which is achieved by detailing the response of the complex groundwater system under high-intensity mining conditions. The method presented in this paper has great significance and applicatory value for obtaining a comprehensive understanding of the disturbance characteristics of human underground engineering activities (e.g., coal mining) on groundwater systems, as well as accurately predicting water inflow. [ABSTRACT FROM AUTHOR]

Currently, the demand for water is rising, and as a result, the groundwater is declining. Water supplies are not sufficient for agricultural productivity, environmental preservation, or ecosystem services, resulting in an unbalanced water budget in the basin. The goal of this paper is to assess the groundwater recharge in the Jedeb sub-basin using WetSpass-MODFLOW coupling. A spatially distributed water balance model is developed to simulate long-term average recharge depending on land cover, soil texture, topography, and hydro meteorological parameters. The groundwater model is iteratively connected to the recharge model in order to simulate recharge. This means that the depth of the groundwater affects the recharge estimate and vice versa. The average yearly evapotranspiration, surface runoff, and groundwater recharge were determined using WetSpass-M to be 574, 898, and 99 mm, respectively. Groundwater recharge accounted for 6.3% of precipitation, while actual evapotranspiration and surface runoff accounted for 36.4% and 57% of precipitation, respectively. In such seasonal variations, the groundwater level in the Jedeb Sub-basin was studied under various stress conditions (dry season, wet season, and annually). The groundwater level distribution varied from 2,052.3 to 3,063.06 m in the summer stress period (recharge). While in the winter stress period (recharge), the groundwater level varied from 2,051.41 to 3,061.92 m, and the groundwater level due to the annual stress period (recharge) varied from 2,053.76 to 3,064.5 m. With a correlation coefficient of.89, which is an acceptable fit between the simulated and observed heads in steady state for all stress periods (summer, winter, and annual recharge). The contribution of this study could be used as baseline information for regional water resource experts, policymakers, and researchers for further investigation. [ABSTRACT FROM AUTHOR]

This paper investigates the optimal remediation process in an aquifer using Modflow 6 software and genetic algorithms. A theoretical confined aquifer has been polluted over a long period of time by unnoticed leakage in a pipeline conveying leachate from an adjacent landfill to a wastewater treatment plant. When the extended leakage and groundwater pollution are discovered, the optimal planning of the remediation strategy is investigated using the pump-and-treat method or/and hydrodynamic control of the pollution. The practical goal is to find the optimal locations and flow rates of two additional pumping wells, which will pump the polluted water or/and control pollution, protecting an existing drinking water pumping well, securing its fully operational mode even during the remediation process with the minimum possible cost, simply represented by the pumped water volume of the additional wells. The remediation process is considered complete when the maximum concentration in the aquifer drops below a certain limit. The Modflow software (handled by the Flopy Python package) simulates the flow field and advective–dispersive mass transport, and a genetic algorithm is used as the optimization tool. The coupled simulation–optimization model, Modflow-GA, complemented by a sophisticated post-processing results analysis, provides optimal and alternate sub-optimal remediation strategies for the decision makers to select from. [ABSTRACT FROM AUTHOR]

The paper investigates the mechanism of seawater intrusion and the performance of free and open-source codes for the simulation of variable density flow problems in coastal aquifers. For this purpose, the research focused on the Marathon Watershed, located in the northeastern tip of Attica, Greece. For the simulation of the groundwater system, MODFLOW, MT3DMS and SEAWAT codes were implemented, while sensitivity analysis and calibration processes were carried out with UCODE. Hydraulic head calibration was performed on the MODFLOW model, and TDS concentration was validated in the SEAWAT model. The calibrated parameters of the MODFLOW model were obtained for the variable density flow simulation with SEAWAT. The MODFLOW and SEAWAT hydraulic head outputs were analyzed and compared to one another. The outcome of this analysis is that SEAWAT produced slightly better results in terms of the hydraulic heads, concluding that parameter transferability can take place between the two models. For the purpose of the seawater intrusion assessment, the use of the SEAWAT code revealed that the aquifer is subjected to passive and passive–active seawater intrusion during wet and dry seasons, respectively. Finally, an irregular shape of a saltwater wedge is developed at a specific area associated with the hydraulic parameters of the aquifer. [ABSTRACT FROM AUTHOR]

Groundwater level (GWL) refers to the depth of the water table or the level of water below the Earth's surface in underground formations. It is an important factor in managing and sustaining the groundwater resources that are used for drinking water, irrigation, and other purposes. Groundwater level prediction is a critical aspect of water resource management and requires accurate and efficient modelling techniques. This study reviews the most commonly used conventional numerical, machine learning, and deep learning models for predicting GWL. Significant advancements have been made in terms of prediction efficiency over the last two decades. However, while researchers have primarily focused on predicting monthly, weekly, daily, and hourly GWL, water managers and strategists require multi-year GWL simulations to take effective steps towards ensuring the sustainable supply of groundwater. In this paper, we consider a collection of state-of-the-art theories to develop and design a novel methodology and improve modelling efficiency in this field of evaluation. We examined 109 research articles published from 2008 to 2022 that investigated different modelling techniques. Finally, we concluded that machine learning and deep learning approaches are efficient for modelling GWL. Moreover, we provide possible future research directions and recommendations to enhance the accuracy of GWL prediction models and improve relevant understanding. [ABSTRACT FROM AUTHOR]

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Aquifer systems, because of the presence of frequently complex geological structures, may extend beyond watersheds limits. Interbasin groundwater flow is often identified among watersheds. Because geological systems are complex ones, modelling tools are needed for its estimation. In this paper, we quantify the outflows from the endhoreic Gallocanta watershed (Spain) by means of a MODFLOW numerical model in order to assess the robustness of the boundaries of the Gallocanta Groundwater Body. Our results show the Gallocanta watershed is hydrogeologically connected with the adjoining Piedra-Ortiz and Jiloca watersheds (discharging annually in these basins about 4 and 1 Mm3 respectively). Furthermore, we hypothesized the presence of geological features altering the groundwater flow. Additional simulations were run to analyse the changes in the water budget in the cases of: i) groundwater pumping no longer allowed by the authorities, and ii) a potential drought scenario. In the first case, the results forecast an increase in discharge to the Piedra-Ortiz and Jiloca watersheds, while in the second case a diminution of the outflows to the two neighboring basins is foreseen. We then propose a larger and unique groundwater body, spanning from the Caminreal Springs on the east and the Piedra-Ortiz basin on the west, including a moving groundwater divide internal to the Gallocanta watershed. Monitoring the baseflow of the Piedra-Ortiz river and of the Caminreal Springs will allow to get information on the evolution of the groundwater resource availability in the Gallocanta watershed. Our results stress the importance of conjunctively using data and traditional geologic knowledge (i.e. surface geology maps) along with numerical modelling analyses. This holds especially true in areas, such those of hard-rock aquifers, where scarce hydrogeologic data are available, to test conceptual models, to derive and to infer information on water budgets and on the presence of relevant structural features driving the groundwater flow. This approach may lead to informed decision-making on groundwater body boundaries definition for the application of relevant groundwater management regulations. [ABSTRACT FROM AUTHOR]

This paper focuses on deriving new approximate analytical solutions in wedge‐shaped aquifers. The proposed methodology is applicable to any type of aquifer namely, leaky, confined and unconfined, under both steady state and transient flow conditions. By applying the method of images and separating the flow field into sections using physical arguments, approximate analytical expressions are obtained for the drawdown function, which in contrast to the conventional theory, are applicable to any arbitrary wedge angle. Moreover, the solutions fully observe the boundary conditions, while they preserve the continuity of the drawdown, which can be calculated directly at any point of the flow field. Nevertheless, comparison of the results of the new approximate analytical solutions to numerical ones, has been considered necessary to check their validity. MODFLOW, a well‐known numerical tool is used to calculate the numerical results. The discrepancies between the numerical results and those of the approximate analytical solution are negligible. The main advantages of the proposed methodology are the following: (a) The model needs only finite number of terms compared to conventional analytical and numerical solutions that involve infinite series, (b) The computational load is low, so it can be easily used in conjunction with meta‐heuristic algorithms to solve groundwater resources optimization problems, (c) Stream depletion rate can be calculated rather accurately and (d) The method is applicable to related flow problems. Key Points: New functions for drawdown calculation in wedge‐shaped aquifers are presentedThe proposed functions are suitable to be used in conjuction with meta‐heuristic algorithms to solve groundwater optimization problemsConvergence of the results obtained from the set of functions and numerical methods (MODFLOW) point out the validity of the proposed solutions [ABSTRACT FROM AUTHOR]

The multi-aquifer system of the Nubian aquifer in central Sudan hydrogeological system was simulated using a three-dimensional steady-state model. The goal of the study is to detect the effect of pumping on the groundwater flow and thus, the aquifer productivity. The conceptual model of the study area was built based on the available geological and hydrogeological data guided by geophysical survey. Processing MODFLOW numerical code was used to calculate the hydraulic head and water balance under the existing boundary conditions. The model accurately simulated the hydraulic head with a determination coefficient of 0.88. The calibrated model indicated that the change in storage is 0.56 m3/day indicating the study area constitutes highly productive zone and is recommended for groundwater developments. [ABSTRACT FROM AUTHOR]

Agricultural intensification has boosted land productivity, but it has also created new sustainability issues. As one of the most important human habitations and agricultural farming areas in arid areas, the Cele Oasis has a very developed agricultural system. This paper studies the long-term effects of different types of agricultural intensification strategies on groundwater level fluctuations in the Cele Oasis. A soil water flow (HYDRUS-1D) and aquifer simulation (MODFLOW) coupling model were used to construct the geometric structures of the vadose zone and saturated zone in the Cele Oasis and to analyze the recharge and discharge mechanism of the oasis. The results showed that HYDRUS-1D accurately simulated soil moisture transport in the Cele Oasis, providing reliable data for calibration of the MODFLOW model. The groundwater level simulated by MODFLOW was in good agreement with the observed value. The results of the R2, RMSE, and NSE were ranges of 0.77–0.90, 0.45–0.74 m, and 0.76–0.87, respectively. The errors were acceptable limits. The coupling model predicted the responses of different agricultural types and cropping scenarios to groundwater. Predictions showed that the groundwater level in the Cele Oasis remained stable under the current cropping scenario (100% cropping intensity), and that the groundwater level decreased slightly under the cropping scenario (110% cropping intensity and 130% cropping intensity). When the cropping scenario was at 170% cropping intensity, the groundwater level decreased rapidly, and the maximum drawdown value was 7 m. Therefore, the maximum cropping intensity of the Cele Oasis in the future should be 130% of the current cropping intensity. [ABSTRACT FROM AUTHOR]

This paper constitutes an assessment of the climate change (CC) impacts on the Zeuss–Koutine (ZK) aquifer in southeastern Tunisia using a WEAP-MODFLOW decision support system (DSS). Efficiency criteria are calculated for hydraulic heads to validate the MODFLOW model. The DSS simulates the behavior of the aquifer while representing demands and other water sources. It is able to evaluate monthly water management scenarios up to 2030. It emphasizes the seriousness of the water resource situation in the region exhausted by the increasing demands and the climate circumstances which leads to the risk of salinization. The DSS shows a calculated aquifer drawdown during the simulation period (1982–2010) of 22.0 m which is exactly the recorded one. To simulate future CC, data are collected from the "Climate Wizard" web site, providing results of 16 general circulation climate models under A2, A1B, and B1 emission scenarios. Based on precipitation changes, three scenarios are deduced: the mean, the worst, and the best CC. Results show that the forecasted average drawdown (2010–2030) would be between 30.5 (1.5 m/year) and 33.9 m (1.7 m/year) under the best and the worst CC scenarios, respectively. The worst CC scenario could lead to the intrusion of brackish lagoon water or even a long-term marine intrusion. The use of the Jerba Sea Water Desalinization Plant (JSWDP), in 2018, would improve the situation, and the average estimated drawdown would be 16.9 m (0.8 m/year) under the mean CC, presenting then an improvement of about 49%. The ZK aquifer would lose 121% of its storage under the coupled JSWDP_mean CC scenario, between 1982 and 2030, presenting an improvement of about 52% compared to CC scenarios. [ABSTRACT FROM AUTHOR]

Objective Hetao Irrigation District relies on Yellow River water for irrigation, but excessive use of the river water had resulted in soil salinity. Jointly using groundwater and river water has been postulated as a feasible mitigation technology, and the purpose of this paper is to present the results of a study on how to achieve optimal use of groundwater and surface water. Method A three-dimensional groundwater model for the region was calibrated and verified using MODFLOW based on measured groundwater depths and other datasets. We then applied the model to four typical well-canal combination areas in four sub-districts: Wulanbuhe, Jiefangzha, Yongji and Yichang. 44 scenarios with four different well-irrigation areas and 11 kinds of canal-well combination ratios were considered. For each scenario, we predicted how the groundwater depth changed with the well-canal combination ratio and well-irrigation area. Result The three-dimensional groundwater model correctly captured physical properties of the aquifers and soils and reproduced the observed change in groundwater depth at different scenarios. When the ratio of well-irrigated to canal- irrigated areas was the same, the average groundwater depth in Jiefangzha and Wulanbuhe was the shallowest followed by Yongji, with that in Yichang the deepest. Isograms of groundwater depth in areas with well-canal irrigation in Wulanbuhe was the densest, followed by Yichang, with Yongji and Jiefangzha the sparsest. When the well-irrigated area was constant, the average groundwater depth decreased asymptoticall as the canal-well combination ratio increased. Conclusion The suitable canal-well combination ratio and well-irrigation area for controlling groundwater depth not exceeding 3 m varied with the sub-districts due to their difference in hydrogeological conditions. The well-irrigation areas in Wulanbuhe, Jiefangzha, Yongji and Yichang should not exceed 12.25 km2, 12.25 km2, 9 km2 and 6.25 km2 respectively, with their associated ratio of canal-irrigated area to well- irrigation area not exceeding 2.5, 2.5, 3.0 and 3.3 respectively. [ABSTRACT FROM AUTHOR]

Climate change is one of the most significant issues facing humanity, and an increased number of countries are proactively addressing this problem. Any changes in water resources brought on by climate change would pose a serious risk to a lot of nations. Egypt is one of these nations which will suffer from climate change. One of the consequences of climate change is sea level rise (SLR), which in turn will lead to the advance of shore line in land and more seawater intrusion. The sea water will advance inland, flooding a significant portion of the good lands, and many inhabitants will leave their homes as a result. The Nile Delta is one of the most vulnerable areas to be inundated by sea water due to the flat topographical nature of the area. Moreover, a large part of the water in the Nile Delta aquifer (NDA) will become saline, and the reservoir will become more vulnerable to Seawater intrusion (SWI) Which is affected not only by the rise in sea level and the advance of shore line, but also by the excessive withdrawal from the pumping wells. In this paper (MODFLOW+SEAWAT+ARC GIS) were used to investigate seawater intrusion in Nile Delta aquifer and to determine the position of the new shore line due to 0.25 m and 0.5 m rise of the Mediterranean sea level in Nile Delta. Owing to the lack of data of the topography of the area, because it need high accuracy of Digital Elevation Model (DEM) the position of shore line is obtained based on analyzing the results of saltwater intrusion due to 0.25 m and 0.5 m of sea level rise of recent studies through SEAWAT and the results were exported to ARC GIS to get maps of new shore line. [ABSTRACT FROM AUTHOR]

Groundwater-dependent agricultural intensification has led to unsustainability of groundwater systems in many parts of the world. The unconfined aquifers in the Eastern Indo-Gangetic Plains (EIGP) of India are one of the most extensive aquifer systems in South Asia and are prone to ever intensifying agricultural systems. This paper aims at evaluating the long-term impacts of agricultural intensification on groundwater dynamics in an agriculturally important sub-region of EIGP. The study proposes a multi-model approach, combining the capabilities of vadose zone model (HYDRUS-1D) and aquifer simulation model (MODFLOW) to analyse the recharge and discharge mechanisms in the alluvial Gangetic Plains. The study mathematically reconstructed the vadose zone and aquifer geometry and implemented them into flow models. We demonstrate that the loosely coupled vadose zone and groundwater flow modelling framework is highly suitable for simulating the impact of changed cropping intensity on groundwater dynamics. The recharge estimates from HYDRUS-1D and calibration of regional groundwater flow model offered a robust set of parameter values for the prevalent conditions of EIGP. The results show good correspondence between the observed and simulated water table levels during calibration, with RMSE = 0.56–0.59 m, NSE = 0.76–0.99 and R2 = 0.83–0.91, all within acceptable limits. Projections showed that although the water table in the region would remain fairly stable under lower levels of cropping intensity (135–150%), further increase to 200 and 300% would lead to water table decline at the rate of 0.87 and 1.83 m per year, respectively. These changes could therefore impact future groundwater risk management in EIGP. This reinforces the view that groundwater-dependent intensification may be sustainable in long term only if adaptation strategies and compensatory measures are adopted. [ABSTRACT FROM AUTHOR]

This study aimed to control land subsidence by improving the groundwater balance in the Varamin plain using the Groundwater Modelling System software and a multi-criteria decision model. For this purpose, aquifer level quantification and subsidence rate simulation were performed with the MODFLOW model and SUB package, respectively. The results showed a 6 m decrease in the aquifer level over a 5-year period and the subsidence rate in the central parts was 37 cm. Accordingly, the aquifer was evaluated by considering eight different restoration strategies based on reduced exploitation and artificial feeding. The results showed that the environmental criterion related to the subsidence adjustment index had the highest weight (0.27) and was introduced as the most important decision-making criterion. The evaluation of the results and priorities using the Complex Proportional Assessment (COPRAS) method showed that a 30% reduction in exploitation with artificial feeding is the best restoration strategy and can improve the subsidence rate and aquifer level by 36% and 76%, respectively, over a 5-year period (2024). [ABSTRACT FROM AUTHOR]

Groundwater, essential for supplying drinking water to half of the global population and supporting nearly half of all irrigation needs, faces significant contamination risks. These risks pose serious threats to human health and ecosystem integrity, driven by increasing pressures from both concentrated and diffuse pollution sources, as well as from growing exploitation. The presented research was conducted with the dual objectives of identifying sources of nitrate contamination (up to 128.1 mg/L) in an oxic groundwater source (Perkićevo, Serbia) and proposing an optimal extraction regimen to ensure a sufficient supply of potable water. Correlations between chemical elements' concentrations and principal component analysis (PCA) indicated a significant relationship between anthropogenic impact indicators (NO3−, Na+, B, Cl−, SO42−, KMnO4 consumption, and electroconductivity), unambiguously showing that groundwater quality was primarily impacted by untreated sewage inflow and confirming nitrate's tracer behavior in oxic environments. The spatial distribution of selected parameter concentration gradients highlighted the expansion and distribution of the contamination front. A numerical groundwater flow model (Vistas 4 and Modflow) was applied to determine the groundwater flow direction and the quantity of groundwater originating from different parts of the investigated area. Through four simulated groundwater extraction scenarios, Scenario 2, with an average extraction rate of 80 L/s from 12 wells, and Scenario 3, with an average extraction rate of 75 L/s and 4 additional wells, were identified as the most optimal, providing a sufficient quantity of adequately sanitary water. [ABSTRACT FROM AUTHOR]

Water scarcity poses a significant challenge in arid and semi-arid regions, necessitating a focused exploration of groundwater resources. Egypt, confronted with various water challenges, particularly in its Western Desert, relies heavily on groundwater as the exclusive water source due to the presence of the Nubian Sandstone aquifer. Effective groundwater management in this region is imperative. This study delves into the hydrogeological characteristics of the Nubian Sandstone aquifer system (NSAS) in the prominent New Valley Oases--Kharga, Dakhla, and Farafra--where agricultural activities heavily depend on groundwater. The primary objective entails a meticulous temporal assessment of the impact of groundwater development on aquifer behavior, groundwater levels, and drawdown. Employing a remote sensing approach, agricultural expansion from 1995 to 2020 was scrutinized. The Visual MODFLOW package served as a robust tool for simulating groundwater flow in the study areas. Noteworthy findings reveal an upward trajectory in agricultural crop areas, escalating by approximately 6% from 1740 km² in 1995 to 1850 km² in 2020. Concurrently, drawdown, influenced by current groundwater extraction, is anticipated to range from 0.5 to 5 meters per year. To ensure the sustainable development of these areas, stringent regulations must be implemented, underscoring the imperative for judicious groundwater management practices. This research underscores the critical need for informed decision-making and proactive measures to address the evolving dynamics of groundwater resources in the New Valley Oases. [ABSTRACT FROM AUTHOR]

With the gradual improvement in coal mining efficiency, the disturbance of groundwater systems caused by high-intensity mining also increases, leading to challenges in maintaining mine safety and protecting water resources in mining areas. How to accurately describe the dynamic changes in the groundwater system under mining and quantitatively predict mine water inflow are currently major problems to be addressed. Based on a full analysis of the response characteristics of a groundwater system to the extraction disturbance, this paper presents a new method to establish a mine hydrogeological conceptual model that can accurately represent the water inrush process. The unstructured-grid package of MODFLOW is used to accurately characterize the formation structure and finally make accurate water inflow predictions. Taking the Caojiatan coal mine in Shaanxi Province, China, as an example, a numerical model of unstructured water inflow is established, and the changes in the water inflow source and intensity are quantitatively evaluated. Compared with the traditional water inflow prediction method, the prediction accuracy of the new model is improved by 12–17%, which is achieved by detailing the response of the complex groundwater system under high-intensity mining conditions. The method presented in this paper has great significance and applicatory value for obtaining a comprehensive understanding of the disturbance characteristics of human underground engineering activities (e.g., coal mining) on groundwater systems, as well as accurately predicting water inflow.

In arid regions, the optimal utilization of river channels to collect rainwater resources can effectively alleviate the problem of water scarcity. This paper employs visual MODFLOW software to simulate the infiltration volume of rainwater under different schemes, with the objective of identifying the optimal infiltration volume. The results indicate that the infiltration volume of rainwater is 0.6, 79.7, 36.5, 62, and 10,000 m3 under different design schemes. COMSOL software is employed to simulate the infiltration situation of rainwater under different schemes, and the scheme with the most favourable infiltration effect is identified. The simulation results indicate that scenarios 2, 4, and 5 demonstrate superior early-stage infiltration performance. Ultimately, the optimal infiltration scheme is selected by integrating the infiltration volume, infiltration effect, construction, economic, and ecological factors to achieve the objective of enhancing rainwater harvesting and utilization. This study offers effective and reasonable measures for addressing the challenge of water resources management in arid regions. It provides suitable reference schemes for river channel rainwater storage projects and offers innovative approaches to rainwater resource utilization, thereby contributing to the alleviation of water scarcity in arid areas.

Metropolitan Tuguegarao Water District is one of Northern Luzon's leading groundwater consumers, averaging a monthly extraction of 1.43 million cubic meters. Since its inception, the water supply system has relied mainly on groundwater, triggering well sources to deteriorate. While recharge through soil moisture accounting is sufficient for safe yield estimation, a groundwater flow model was created to account for the spatiotemporal distribution of groundwater levels in response to hydraulic and hydrologic stresses. MODFLOW, a finite-difference model, aided in the development of local grids from a regional basin--the Cagayan Valley Aquifer System. A three-dimensional numerical flow model was satisfactorily calibrated, with the goodness offit between the simulated and observed heads determined through three statistical indices: Mean Absolute Error (0.5376 m), Root-Mean-Squared Error (0.8061 m), and Normalized Root-Mean-Squared Error (2.23%). The model simulated a 10.60% recharge from rainfall for the regional basin, which is comparable to the average recharge rate estimated by the Department of Environment and Natural Resources. Continuous pumping demonstrated head reductions that exceeded critical levels in four wells at current rates, 12 wells at adjusted rates, and five wells affected by pumping the proposed wells. Notably, four production wells, which constitute 31% of the present groundwater production, remained below critical levels. With the proposed surface water facility, however, groundwater production may be reduced up to 63%, allowing for the resource to recover. The findings of this research on all model scenarios showed that groundwater levels will decrease in the coming years. Thus, efficient planning for sustainable resource use is crucial. This study presents the relevance of numerical hydraulic analysis for a more comprehensive groundwater resource assessment. [ABSTRACT FROM AUTHOR]

This study presents the development of a comprehensive three-dimensional groundwater flow model for the Erbil Basin utilizing the Groundwater Modeling System (GMS). The Erbil Basin, situated in the Kurdistan Region of Iraq, is a vital water resource area facing increasing water demands and environmental challenges. The three-dimensional nature of the groundwater flow system is crucial for accurately understanding and managing water resources in the basin. The modeling process involved data collection, geological and hydrogeological characterization, conceptual model development, and numerical simulation using GMS software MODFLOW 2000 package. Various parameters such as hydraulic conductivity, recharge rates, and boundary conditions were integrated into the model to represent the complex hydrogeological conditions of the basin. Model calibration was performed by comparing simulated groundwater levels with observed data from monitoring wells across the basin, using the automatic calibration method of automated Parameter Estimation (PEST). Pilot points were applied to adjust the hydraulic conductivity in the model area spatially. Sensitivity analysis was conducted to assess the influence of key parameters on model predictions and to identify areas of uncertainty. The developed three-dimensional groundwater flow model provides valuable insights into the dynamics of groundwater flow, recharge-discharge mechanisms, and potential impacts of future scenarios such as climate change and water resource management strategies. It serves as a useful tool for decision-makers, water resource managers, and researchers to evaluate different management scenarios and formulate sustainable groundwater management policies for the Erbil Basin. In conclusion, this study demonstrates the effectiveness of using GMS for developing three-dimensional groundwater flow models in complex hydrogeological settings like the Erbil Basin, contributing to improved understanding and management of groundwater resources in the region. [ABSTRACT FROM AUTHOR]

Abstract Aquifer systems, because of the presence of frequently complex geological structures, may extend beyond watersheds limits. Interbasin groundwater flow is often identified among watersheds. Because geological systems are complex ones, modelling tools are needed for its estimation. In this paper, we quantify the outflows from the endhoreic Gallocanta watershed (Spain) by means of a MODFLOW numerical model in order to assess the robustness of the boundaries of the Gallocanta Groundwater Body. Our results show the Gallocanta watershed is hydrogeologically connected with the adjoining Piedra-Ortiz and Jiloca watersheds (discharging annually in these basins about 4 and 1 Mm3 respectively). Furthermore, we hypothesized the presence of geological features altering the groundwater flow. Additional simulations were run to analyse the changes in the water budget in the cases of: i) groundwater pumping no longer allowed by the authorities, and ii) a potential drought scenario. In the first case, the results forecast an increase in discharge to the Piedra-Ortiz and Jiloca watersheds, while in the second case a diminution of the outflows to the two neighboring basins is foreseen. We then propose a larger and unique groundwater body, spanning from the Caminreal Springs on the east and the Piedra-Ortiz basin on the west, including a moving groundwater divide internal to the Gallocanta watershed. Monitoring the baseflow of the Piedra-Ortiz river and of the Caminreal Springs will allow to get information on the evolution of the groundwater resource availability in the Gallocanta watershed. Our results stress the importance of conjunctively using data and traditional geologic knowledge (i.e. surface geology maps) along with numerical modelling analyses. This holds especially true in areas, such those of hard-rock aquifers, where scarce hydrogeologic data are available, to test conceptual models, to derive and to infer information on water budgets and on the presence of relevant structural features driving the groundwater flow. This approach may lead to informed decision-making on groundwater body boundaries definition for the application of relevant groundwater management regulations.

This study investigated the interaction of groundwater flow and foundation piles located in the vicinity of the Danube River. The piles represent an obstacle to the groundwater flow, causing a backwater effect upstream whilst increasing the local flow velocity. On the other hand, a high flow velocity around the piles can cause suffusion of the surrounding soil in the long term, thus significantly reducing the shaft resistance of the piles. A 3D model of groundwater flow and its impact on the piles was developed in the software 10.3 package GMS based on MODFLOW 2005. The model was calibrated by comparing the calculated results with the measured values in the control well for different values of the filtration coefficients. In the calibration process, foundation piles were not applied in the model. After the calibration process, the piles were implemented into the model and the underground flow was simulated in the study area for the calibrated year 2006. The impact analysis was carried out by comparing the groundwater level change over time in the pile zone at three control points, in cases with and without the piles, along with the flow net analysis at the piles' location. The results indicate no influence of the piles on the groundwater flow in the study area, both in terms of critical flow velocities and a possible backwater effect upstream. [ABSTRACT FROM AUTHOR]

Groundwater modeling is a useful tool for assessing sustainability in water resources planning. However, groundwater models are difficult to construct in regions with limited data availability, areas where planning is most crucial. We illustrate how remote sensing data can be used with limited in situ data to build and calibrate a regional groundwater model in the Goulbi Maradi alluvial aquifer in southern Niger in Western Africa. We used data from the NASA Gravity Recovery and Climate Experiment (GRACE) satellite mission to estimate recharge rates, the primary source of water to the aquifer. We used the groundwater storage changes obtained from GRACE data from 2009 to 2021 to establish an overall water budget. We used this water budget to back-calculate groundwater withdrawals from pumping in the region. There are only very limited historic data on withdrawals. This approach allowed us to calibrate the model and use it as a predictive tool to analyze the impact of various assumptions about future recharge and groundwater extraction patterns associated with the development of groundwater infrastructure in the region. The results indicate that water extraction from the Goulbi Maradi alluvial aquifer is sustainable, even if current groundwater extraction is increased by up to 28%. [ABSTRACT FROM AUTHOR]

It is important to clarify the suitable ratio of well–canal combined irrigation and the suitable range for ecological groundwater depth for the ecological stability of the arid zone. The MODFLOW model was used to reconstruct long-term groundwater depth by analyzing the response relationship between vegetation cover and groundwater depth in the Weigan River irrigation district. The suitable range for ecological groundwater depth was obtained, and based on this range, the suitable well–canal combined irrigation ratio in the research area was further simulated. The results show the following: (1) The average annual depth of groundwater in 82.9% of the study area increased from 2012 to 2021, and the average annual depth of groundwater increased by 1.03 m in 2021 compared to 2012. The average depth of the groundwater in the upstream area increased the most, with an increase of 1.96 m. (2) The vegetation cover in the study area from 2012 to 2021 increased in general, with an increase of 0.0461 over the 10-year period, but it fluctuated between years. (3) The depth of the groundwater in the study area suitable for the growth of vegetation in the irrigation area ranged from 3 to 5 m, and the value of NDVI within this range concentrated near 0.564–0.731, which represents a good state of vegetation growth. (4) The ratio of combined well and canal irrigation in the study area from 2012 to 2014 surged from 0.13 in 2012 to 0.48 in 2014, and the irrational harvesting and replenishment relationship led to a rapid increase in the depth of buried groundwater. A suitable well–canal combined irrigation ratio of 0.396 in the study area was obtained. This study is beneficial for maintaining the sustainable development and utilization of water resources and ecological stability in the Weigan River irrigation district. [ABSTRACT FROM AUTHOR]

The paper investigates the mechanism of seawater intrusion and the performance of free and open-source codes for the simulation of variable density flow problems in coastal aquifers. For this purpose, the research focused on the Marathon Watershed, located in the northeastern tip of Attica, Greece. For the simulation of the groundwater system, MODFLOW, MT3DMS and SEAWAT codes were implemented, while sensitivity analysis and calibration processes were carried out with UCODE. Hydraulic head calibration was performed on the MODFLOW model, and TDS concentration was validated in the SEAWAT model. The calibrated parameters of the MODFLOW model were obtained for the variable density flow simulation with SEAWAT. The MODFLOW and SEAWAT hydraulic head outputs were analyzed and compared to one another. The outcome of this analysis is that SEAWAT produced slightly better results in terms of the hydraulic heads, concluding that parameter transferability can take place between the two models. For the purpose of the seawater intrusion assessment, the use of the SEAWAT code revealed that the aquifer is subjected to passive and passive–active seawater intrusion during wet and dry seasons, respectively. Finally, an irregular shape of a saltwater wedge is developed at a specific area associated with the hydraulic parameters of the aquifer.

The Hueco Bolson aquifer is a binational aquifer shared by the United States of America (USA) and Mexico that is strongly interconnected with the transboundary river, Rio Grande/Rio Bravo. Limited recharge, increasing urbanization, and intensified agriculture have resulted in the over-drafting of groundwater resources and stressed the aquifer, threatening its sustainability if mitigation actions are not taken soon. Research indicates that the aquifer's hydraulic gradients and flow directions have changed due to the high groundwater withdrawal rates from the two major cities—El Paso (USA) and Ciudad Juarez (Mexico). This paper presents a comprehensive overview of the Hueco Bolson aquifer modeling history and makes a case for future modeling and binational engagement efforts. First, we discuss the evolution of groundwater modeling for Hueco Bolson from the past to recent times. Second, we discuss the main water management issues in the area, including water quality and quantity, stakeholders' participation, and climate change. To address the challenges of holistic water management, we propose developing a graphical quantitative modeling framework (e.g., system model and Bayesian belief network) to include experts' opinions and enhance stakeholders' participation in the model. Though the insights are based on a case study of Hueco Bolson, the approaches discussed in this study can provide new strategies to overcome the challenges of managing a transboundary aquifer. [ABSTRACT FROM AUTHOR]

Assessing the relationship between Surface Water (SW) and Groundwater (GW) is an important aspect of hydrology, as it aids in the conjunctive and effective management of water resources. This study characterized the surface–groundwater interaction in the Modjo River catchment, central Ethiopia using the Soil and Water Assessment Tool (SWAT) and MODFLOW models. The SWAT model adequately simulated the hydrology of the study area for the calibration (2007–2011, R2 = 0.83) and validation (2012–2015, R2 = 0.7) periods. The semi-distributed average GW recharge from the SWAT model simulation with other hydrogeologic parameters and boundary conditions was utilized to construct the GW flow model using the MODFLOW–NWT version. The integrated modeling result showed that about 43Mm3 of water leaks to the groundwater system annually, whereas the flux from GW to rivers is about 165Mm3/yr. Most reaches of the Modjo River in the northern and central areas of the catchment are gaining, with fluxes reaching up to 4940 m3/day. The downstream part of the catchment is characterized by a losing-disconnected river, with a lower flux of up to 675m3/day. In general, most reaches of the Modjo River are interconnected with the GW system and the GW inflow to streams is higher. Based on these findings, future exploitation and management of both SW and GW resources should consider the nature of their interconnection for sustainable utilization of the water resources in the catchment. [ABSTRACT FROM AUTHOR]

In this study, we present artificial neural networks (ANNs) to aid in a reconnaissance evaluation of an aquifer storage and recovery (ASR) well. Recovery effectiveness (REN) is the proportion of ASR-injected water recovered during subsequent extraction from the same well. ANN-based predictors allow rapid REN prediction without requiring preparation for and execution of solute transport simulations. REN helps estimate blended water quality resulting from a conservative solute in an aquifer, extraction for environmental protection, and other uses, respectively. Assume that into an isotropic homogenous portion of an unconfined, one-layer aquifer, extra surface water is injected at a steady rate during two wet months (61 days) through a fully penetrating ASR well. And then, water is extracted from the well at the same steady rate during three dry months (91-day period of high demand). The presented dimensionless input parameters were designed to be calibrated within the ANNs to match REN values. The values result from groundwater flow and solute transport simulations for ranges of impact factors of unconfined aquifers. The ANNs calibrated the weighting coefficients associated with the input parameters to predict the achievable REN of an ASR well. The ASR steadily injects extra surface water during periods of water availability and, subsequently, steadily extracts groundwater for use. The total extraction volume equaled the total injection volume at the end of extraction day 61. Subsequently, continuing extraction presumes a pre-existing groundwater right. [ABSTRACT FROM AUTHOR]

Groundwater is one of the most important sources of water supply in arid and semi-arid regions, but its availability with sustainable quantity and quality is threatened by various factors, among which climate and land-use change have the most important role. Therefore, it is essential to achieve reliable methods for predicting changes in aquifer storage to plan for the sustainable use of groundwater resources. This study aimed to estimate the potential impact of climate change and land use on the groundwater level of Hashtgerd plain for sustainable use of groundwater resources. In this regard, groundwater supply and demand for 2020 as the base year was simulated to forecast the trends until 2050 by considering climate and land-use changes. Five General Circulation Models under four Representative Concentration Pathways (RCP2.6, RCP4.5, RCP6, and RCP8.5) were used to project future rainfall and temperature. The LARS-WG model was used to downscale the climatic data. Classification of land-use was performed using Landsat satellite images of 1990, 2005, and 2020 in ENVI 5.3 software. Then, by these maps, the Markov chain method implemented in TerrSet software was used to model land-use change for 2050. The indexes used to evaluate the model were the overall accuracy of prediction and the kappa coefficient. The overall accuracy of 94.34% and kappa coefficient of 0.92 were in the calibration stage and 86.34 and 0.82 in the validation stage, respectively. Finally, the effect of climate and land-use change on the decrease of groundwater level was simulated using the MODFLOW model for the period 2020–2050. RMSE and MAE values of steady-state calibration were 0.91 and 0.75, respectively. These values were estimated to be 0.97 and 0.8 in the calibration step for the unsteady-state and 1.01 and 0.91, respectively, in the validation step. The results of climate change showed a decrease in the average annual precipitation and an increase in the average annual temperature. The annual temperature increased by 1.4 °C and 3.2 °C for RCP 4.5 and 8.5 respectively, by 2050. The annual precipitation decreased by 2.45% and 4.47% for both scenarios. The results of land-use change show an increase of residential, barren, and agricultural lands by 105, 41, and 8%, respectively, and a decrease of 94% in pastures lands. The future land-use change reduced aquifer reserve by up to 41%. The combined impacts of climate and land-use change in the most critical state reduced aquifer reserve by 61%. [ABSTRACT FROM AUTHOR]

Egypt has recently inaugurated a mega development project aiming to alleviate the overpopulation along the Nile River and to meet the looming food gap. Toshka is a promising area where groundwater-dependent activities are being expanded adjacent to Lake Nasser. Thus, it is of utmost importance to provide a sustainable development approach and to assess the resulting environmental implications. Accordingly, a coupled groundwater flow and transport model was invoked. The generated model was successfully calibrated for the observed water levels and salinity. The proposed exploitation regime of 102 wells each pumping 1000 m3/day was simulated for a 100-year test period. The maximum resulting drawdown was about 25 m, compatible with the advocated sustainable restriction limit. Climate change (CC) impacts of reducing the lake's storage and increasing the crops' water requirements were investigated. The lake's water level fluctuations were a key factor in the aquifer hydraulics and flow direction. The drawdown breakthrough considering the CC catastrophic scenario (RCP8.5) has increased by about 20%. The developed solute transport model was utilized to simulate the salinity spatial distribution and the lateral movement of leaking pollutants from the underway activities. Cultivation activities were found feasible up to 80 km away from the lake border where salinity does not exceed 2000 ppm. Yet, a protection strip of not less than 4.8, 6.0, and 7.2 km according to the lake operating condition is inevitable to ensure that pollutants do not intrude into the lake. These findings will assist the decision-makers in scheming environmental impact assessment criteria for sustainable development. [ABSTRACT FROM AUTHOR]

Winter deicers are a major source of chloride contamination to shallow aquifers in northern latitudes. In the greater Chicago area of northeast Illinois, chloride has been accumulating for decades and in many places now exceeds the United States Environmental Protection Agency secondary standard of 250 mg/L. MODFLOW‐NWT and MT3D‐USGS were used to simulate the accumulation of chloride with 30 years of data in the shallow aquifer of Will County in northeast Illinois. This aquifer is composed of unconsolidated sediments, largely from glacial deposits, overlying a fractured dolomite bedrock. To calibrate to observed heads and chloride, the model needed refined geologic features, higher chloride concentrations on cells representing commercial or industrial lands, lower chloride concentrations on cells representing roads, and point source areas to speed chloride's emergence in the aquifer. These point sources are locally significant and could represent different anthropogenic or geologic features, such as municipal stormwater infrastructure. Future simulations indicate that chloride is not at steady state in the shallow aquifer and wells are at risk of exceeding the secondary standard if winter deicing applications are not reduced. It may take decades for the full impacts of reduced deicing rates to be observed in wells, owing to the long residence time of water in the aquifer. This transient model calibration was possible because of the 30‐year dataset collected by communities and government agencies. [ABSTRACT FROM AUTHOR]

The study proposes a stochastic approach to quantify the uncertainty of groundwater vulnerability (GV) produced by classical index-overlay methods. In the analysis, the physical-based MODFLOW model has been integrated with the DRASTIC method and modified by the analytical hierarchy process (AHP) technique. Specifically, the flow fields from the MODFLOW model provide the parameters of depth to water and the associated hydraulic conductivity (K) for the DRASTIC method. The integrated loops between the MODFLOW and DRASTIC models enable the evaluations of GV maps by considering sources of uncertainty in geological parameters and stress changes in an aquifer system. In illustrating the approach for practical implementations, the study considers the uncertainty produced by the heterogeneity of K in the Pingtung Plain groundwater basin in southern Taiwan. Different degrees of K heterogeneity were assessed to quantify the impact of the K heterogeneity on the GV mappings. Results show that the integration of parameter uncertainty information from the stochastic-based approach for GV mapping can improve the accuracy and reliability of the GV assessment. The stochastic GV maps have accounted for the source of the K uncertainty. There are significant discrepancies in GV values in the spatial distribution and intensity in all GV classes. The results clarify the potential risk of groundwater contamination in the Pingtung Plain groundwater basin. [ABSTRACT FROM AUTHOR]

Global climate change-induced stresses on coastal water resources include water use restrictions, saline intrusions, and permanently modifying or damaging regional resources. Groundwater in coastal regions is often the only freshwater resource available, so an in-depth understanding of the aquifer, and the aquifer's response to climate change, is essential for decision-makers. In this study, we focus on the coastal aquifer of Roussillon (southern France) by developing and investigating a steady-state groundwater flow model (MODFLOW 6) and calibrated with PEST++ on a Python interface (FloPy and PyEmu). Model input and boundary conditions are constrained by various scenarios of climate projections by 2080, with model results predicting the aquifer's response (and associated uncertainty) to these external forcings. Using simple assumptions of intrusion estimates, model results highlight both strong climatic and anthropogenic impacts on the water table. These include aquifer drawdowns reaching several meters locally, and the seawater interface advancing locally several hundred meters inland and rising by several meters. Intrusions of this magnitude risk endangering exploited water wells and their sustainability. Our results demonstrate the critical importance of properly characterizing the geology and its heterogeneity for understanding aquifers at risk because poor predictions may lead to inappropriate decisions, putting critical resources at risk, particularly in coastal environments. [ABSTRACT FROM AUTHOR]

Groundwater flow modeling is commonly used to calculate groundwater heads, estimate groundwater flow paths and travel times, and provide insights into solute transport processes within an aquifer. However, the values of input parameters that drive groundwater flow models are often highly uncertain due to subsurface heterogeneity and geologic complexity in combination with lack of measurements/unreliable measurements. This uncertainty affects the accuracy and reliability of model outputs. Therefore, parameters' uncertainty must be quantified before adopting the model as an engineering tool. In this study, we model the uncertain parameters as random variables and use a Bayesian inversion approach to obtain a posterior, data-informed, probability density function (pdf) for them: in particular, the likelihood function we consider takes into account both well measurements and our prior knowledge about the extent of the springs in the domain under study. To keep the modelistic and computational complexities under control, we assume Gaussianity of the posterior pdf of the parameters. To corroborate this assumption, we run an identifiability analysis of the model: we apply the inversion procedure to several sets of synthetic data polluted by increasing levels of noise, and we determine at which levels of noise we can effectively recover the "true value" of the parameters. We then move to real well data (coming from the Ticino River basin, in northern Italy, and spanning a month in summer 2014), and use the posterior pdf of the parameters as a starting point to perform an uncertainty quantification analysis on groundwater travel-time distributions. [ABSTRACT FROM AUTHOR]

Salinity can have major detrimental impacts on soil health, crop yield, and environmental ecosystem services. In this paper we introduce SWAT-MODFLOW-Salt, a version of SWAT-MODFLOW that simulates the fate and transport of major salt ions (SO 4 2−, Cl−, CO 3 2−, HCO 3 −, Ca2+, Na+, Mg2+, K+) in watershed systems, and focus on its development and application to irrigated stream-aquifer systems. The modeling code accounts for water and salt mass storage in soils, aquifer, and streams, and the movement of water and salt mass in surface runoff, soil lateral flow, percolation and recharge, groundwater flow, and groundwater-surface water exchange. The model is applied to a highly managed, irrigated 700 km2 region of the saline Lower Arkansas River Valley in Colorado, USA. The model is tested against groundwater salt concentrations and in-stream salt mass loadings, and then used to quantify the impact of soil salinity on crop yield. • We provide a new version of SWAT-MODFLOW that simulates salt ion transport in watershed systems • Salt ions are subject to all major hydrologic fluxes and precipitation-dissolution of salt minerals • The SWAT-MODFLOW-Salt code is applied to a saline stream-aquifer system in Colorado • The model can be used for salinity management scenario analysis [ABSTRACT FROM AUTHOR]

MODFLOW is a modular hydrologic model developed by the United States Geological Service since 1984. The last version, MODFLOW 6, allows the use of finite volume (FV) general unstructured grid approach to solve the groundwater flow equations. The FV method entails constraints that are implicitly satisfied by a Voronoi discretization. In this paper, new versions of the freeware VORO2MESH and TOUGH2Viewer tools are presented for Voronoi grid generation for MODFLOW. Originally developed for the TOUGH family of codes, both software has been improved to also work with MODFLOW. VORO2MESH and TOUGH2Viewer have been applied to two case studies and the results have been compared with analytical solutions. Outcomes have demonstrated that VORO2MESH grids give simulation results very close to locally refined Grids created using the Quadtree approach; furthermore, the simulation activities are substantially enhanced using TOUGH2Viewer. • New pre and post processing tools for MODFLOW-compliant Voronoi grids are presented. • VORO2MESH allows the generation of unstructured MODFLOW-compliant Voronoi grids. • TOUGH2Viewer allows visualization of MODFLOW simulations performed on Voronoi grids. • TOUGH2Viewer allows the export of MODFLOW results to PARAVIEW. [ABSTRACT FROM AUTHOR]