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The article discusses the depletion of rivers and groundwater due to climate change and human activity, which poses a threat to water security and ecosystems. Initiatives such as river ecological restoration and groundwater artificial recharge have been implemented to mitigate this trend. However, these actions can alter the natural connections between river water and groundwater, impacting their hydrological characteristics and material exchange. The article introduces a special issue that aims to further understand these behaviors and mechanisms through fifteen papers covering three research fields: hydrobiogeochemical cycles in riverbank filtration, behavior of pollutants in river-groundwater systems, and the impact of climate change and human activities on groundwater dynamics. These papers provide valuable scientific evidence for the sustainable management of water resources and the protection of water ecological security. [Extracted from the article]

This article summarizes a special issue of the journal Water, which focuses on the 11th International Symposium on Managed Aquifer Recharge (ISMAR 11). The papers in this special issue discuss the importance of managed aquifer recharge (MAR) for sustainability worldwide, particularly in the face of water-related events like floods and droughts. The articles cover a range of topics including cost-benefit analysis, stakeholder engagement, and climate change adaptation. The research presented in the articles provides valuable insights into the benefits and feasibility of MAR for addressing water shortages and environmental challenges. The text also mentions the potential future focus on information technologies in MAR and the importance of web resources for sharing research results. [Extracted from the article]

Water-resource challenges, encompassing both quality and quantity, pose significant threats to Florida's ecosystems, especially in the face of climate change, rising sea levels, and rapid urbanization. This paper explores the innovative stormwater-management system implemented at Naples Botanical Garden as a model for addressing these challenges. The Garden's approach, treating stormwater as a valuable resource, involves dry and wet retention areas, created lakes, and a unique River of Grass, mimicking natural ecosystems. This system not only mitigates flooding, but also effectively removes pollutants, recharges the aquifer, and provides a habitat for diverse wildlife. The paper emphasizes the economic, environmental, and social impacts of traditional stormwater-management practices in Florida. Naples Botanical Garden's case serves as a guide for botanical gardens and zoos globally, showcasing the pivotal role these institutions can play in sustainable water-resource management. The collaborative design process involving landscape architects, engineers, and horticulturists ensures a holistic and aesthetically pleasing approach to stormwater management. The paper underscores the role of botanical gardens in promoting nature-based solutions, educating the public, and offering tangible steps for implementing similar systems worldwide. It can help guide regional adaptation strategies to manage stormwater as a resource. [ABSTRACT FROM AUTHOR]

This document provides an overview of the use of environmental isotopes in hydrogeology, focusing on the importance of groundwater as a vital resource and addressing issues such as water scarcity, overexploitation, and contamination. It explains how isotopes can be used to identify the origin and replenishment rates of groundwater systems, assess groundwater contamination, and understand groundwater dynamics. The document includes research papers that demonstrate the application of isotopes in various hydrogeological contexts. It concludes by emphasizing the need for comprehensive isotopic studies to support the sustainable management of groundwater resources. The authors express gratitude to the researchers and reviewers who have contributed to a Special Issue and acknowledge the valuable comments that have improved the outcome of the issue. [Extracted from the article]

Jiamusi is situated in Heilongjiang Province, China, in the center of the Sanjiang Plain. The 1980s' overplanting of paddy fields resulted in a decrease in groundwater levels, scarcity of groundwater resources, and frequent earth collapses. Examining and safeguarding the groundwater resources in this region has emerged as a crucial subject. In light of this, this paper uses the remote sensing water balance method and the SWAT distributed hydrological model to calculate groundwater resources in the Jiamusi area. It also conducts scientific experiments by examining various factors, including rainfall, the degree of water supply, soil type, and land use. The measured monthly runoff of Jiamusi City's Tongjiang and Fuyuan City's hydrology stations was utilized to establish the model parameters for the SWAT model. A preliminary assessment of the distribution features of shallow groundwater in the Jiamusi area is conducted using the two methodologies mentioned above, and the following results are reached: (1) Tongjiang Hydrological Station and Fuyuan Hydrological Station both had good runoff modeling results, with R2 and NS values of 0.81, 0.77, and 0.77, 0.75, respectively. (2) The SWAT model works well for assessing groundwater resources. Between 2010 and 2016 (two preheating years), Jiamusi's average groundwater recharge was 61.03 × 108 m3, with a recoverable amount of 27.4 × 108 m3. (3) Based on the remote sensing water balancing approach, the average exploitable quantity of groundwater recharge in the Jiamusi area between 2008 and 2016 is 23.94 × 108 m3, while the average recharge in the area is 53.2 × 108 m3. (4) The Jiamusi metropolitan area is the core of the groundwater phreatic reservoir water reserves, which progressively decline in both the northeast and southeast directions. It falls to the southwest as Fuyuan City's center. The Songhua River's main stream area near Tongjiang City has the least volume of water reserves in the phreatic layer, and the area's groundwater reserves converge to the southeast and northwest, where surface water makes up the majority of the water resources. [ABSTRACT FROM AUTHOR]

Stable isotopes in natural water bodies serve as hydrologic tracers, with a history of extensive application in karst groundwater research. The present paper is a systematic review of previous research results, with the objective of sorting out and summarizing the stable isotopic characteristics of karst groundwater in southwest China, which is the most typical karst region worldwide. Comprehensive analysis reveals that the deuterium and oxygen isotope values of most karst groundwater are characterized temporally as 'enriched in the rainy season and depleted in the dry season', which is the opposite of the pattern of precipitation. While the spatial distribution feature is basically consistent with the spatial variation pattern of precipitation, which is characterized as 'depleted from the coast to the interior'. Additionally, the main applications of stable isotopes to karst groundwater are discussed, including karst groundwater recharge source and recharge elevation identification, research on karst groundwater in the hydrological cycle, the hydrological process of karst groundwater, and karst groundwater contamination tracking. Finally, we looked forward to future research on karst groundwater based on deuterium and oxygen isotopes. It is our hope that this review may provide insight into the study of karst groundwater. [ABSTRACT FROM AUTHOR]

The increasing interest in hydrological studies in the United Arab Emirates (UAE) has resulted in the publication of several papers on hydrology and its broad use for addressing contemporaneous challenges confronting humans and the environment in the region. However, for several reasons, these efforts have remained invisible and unrecognized. This paper has reviewed the literature on hydrological research in the UAE to provide a comprehensive source of information for researchers, practitioners, policymakers, and other stakeholders. The documented studies were carefully selected, relying on a bibliometric analysis methodology of five phases to specify the boundary of the study area, adopt the primary keywords for the search, evaluate the obtained papers, exclude the non-conforming ones, and classify the final results into four distinguished topics—namely, rainfall analysis, urban growth and flood hazards, cloud seeding and changing climate, and groundwater situation and utilization. The evaluation process considered assessing the papers' relevancy, authenticity, and coverage of the main issues of interest. In all, a total of 50 published papers were identified based on the specified criteria and reviewed. The main findings were first that the amount of rainfall over the UAE has been declining in the last decade, and this trend is expected to continue, although intensities are rising, suggesting shorter duration events. Secondly, the extensive urban growth in the country has resulted in increasing incidences of urban floods and declining groundwater recharge. Both of these are to be expected as consequences of the increased imperviousness from urbanization and the higher intensities from shorter-duration rainfall events. Thirdly, although the cloud-seeding program has proved to be successful in increasing precipitation amounts, the impact of this on flooding due to more extreme rainfall intensities and on air quality remains worrisome. Finally, groundwater analyses have shown that it is still the main freshwater resource in the country, but its long-term sustainability and quality are being threatened by the declining recharge. This calls for a national policy for groundwater management in the UAE to tackle the challenges associated with the increasing demand for water in all sectors of the economy. The study recommended addressing the gap in the hydrological literature of the UAE, specifically in the field of big meteorological data analysis, the socioeconomic impacts of urban floods, the impacts of climate change in urbanized regions, and the possibility of using alternative resources to recharge groundwater as part of sustainable water management. [ABSTRACT FROM AUTHOR]

Managed Aquifer Recharge (MAR) and water banking are of increasing importance to water resources management. MAR can be used to buffer against drought and changing or variable climate, as well as provide water to meet demand growth, by making use of excess surface water supplies and recycled waters. Along with hydrologic and geologic considerations, economic and policy analyses are essential to a complete analysis of MAR and water banking opportunities. The papers included in this Special Issue fill a gap in the literature by revealing the range of economic and policy considerations relevant to the development and implementation of MAR programs. They illustrate novel techniques that can be used to select MAR locations and the importance and economic viability of MAR in semi-arid to arid environments. The studies explain how MAR can be utilized to meet municipal and agricultural water demands in water-scarce regions, as well as assist in the reuse of wastewater. Some papers demonstrate how stakeholder engagement, ranging from consideration of alternatives to monitoring, and multi-disciplinary analyses to support decision-making are of high value to development and implementation of MAR programs. The approaches discussed in this collection of papers, along with the complementary and necessary hydrologic and geologic analyses, provide important inputs to water resource managers. [ABSTRACT FROM AUTHOR]

The aim of this paper is to assess the correlation of groundwater level changes (or groundwater level anomalies (GWLA)) obtained from direct measurements in wells with groundwater storage anomalies (GWSA) calculated using Gravity Recovery and Climate Experiment (GRACE) products and Global Land Data Assimilation Systems (GLDAS) models across different climate zones, from temperate Poland to Arctic Sweden. We recognize that such validation studies are needed to increase the understanding of the spatio-temporal limits of remote sensing model applicability, not least in data-scarce sub-Arctic and Arctic environments where processes are complex due to the impacts of snow and (perma) frost. Results for temperate climates in Poland and southern Sweden show that, whereas one of the models (JPL_NOAH_GWSA) failed due to water balance term overestimation, the other model (CSR_CLM_GWSA) produced excellent results of monthly groundwater dynamics when compared with the observations in 387 groundwater wells in the region during 2003–2022 (cross-correlation coefficient of 0.8). However, for the sub-Arctic and Arctic northern Sweden, the model suitable for other regions failed to reproduce typical northern groundwater regimes (of the region's 85 wells), where winter levels decrease due to the blocking effect of ground frost on groundwater recharge. This suggests, more generally, that conventional methods for deriving GWSA and its seasonality ceases to be reliable in the presence of considerably infiltration-blocking ground frost and permafrost (whereas snow storage modules perform well), which hence need further attention in future research. Regarding long-term groundwater level trends, remote sensing results for southern Sweden show increasing levels, in contrast with observed unchanged to decreasing (~10 mm/a) levels, which may not necessarily be due to errors in the remote sensing model but may rather emphasize impacts of anthropogenic pressures, which are higher near the observation wells that are often located in eskers used for water supply. For sub-Arctic and Arctic Sweden, the (relatively uncertain) trend of the remote sensing results nevertheless agrees reasonably well with the groundwater well observations that show increasing groundwater levels of up to ~14 mm/a, which, e.g., is consistent with reported trends of large Siberian river basins. [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]

Coordinating management of groundwater, surface water, and irrigated crops is fundamental economically for many arid and semi-arid regions. This paper examines conjunctive water management for agriculture using hydro-economic optimization modeling. The analysis is integrated across two timescales: a two-stage stochastic decadal model for managing annual and perennial crops spanning dry and wet years and a far-horizon dynamic program embedding the decadal model into a longer groundwater policy setting. The modeling loosely represents California's San Joaquin Valley and has insights for many irrigated arid and semi-arid regions relying on groundwater with variable annual hydrology. Results show how conjunctive water management can stabilize crop decisions and improve agricultural profitability across different water years by pumping more in dry years and increasing recharging groundwater in wetter years. Using groundwater as a buffer for droughts allows growing more higher-value perennial crops, which maximizes profit even with water-scarce conditions. Nevertheless, ending overdraft in basins with declining groundwater for profit-maximizing farming reduces annual crops to maintain more profitable perennial crops through droughts. Results are affected by economic discount rates and future climates. Operating and opportunity costs from forgone annual crops can reduce aquifer recharge early in regulatory periods. [ABSTRACT FROM AUTHOR]

This paper investigates porous concrete and the influence of water level variations and porosity on the mechanical, physical, and hydraulic properties of porous concrete. The effect of different void percentages and various water levels on the properties of porous concrete was studied. Fabricated specimens with targeted porosities of 20% and 25% were subjected to a series of tests to evaluate their compressive strength, hydraulic conductivity (permeability), and porosity. The permeability of the specimens was assessed using a falling head permeameter to ensure effective water percolation. Porosity was quantified through a volumetric method, providing insights into void content. Both cubical and cylindrical specimens were used for all tests, along with compression tests under both air-dried and oven-dried conditions. The results showed that the maximum compressive strength occurred under oven-dried conditions for both cubical (7.05 MPa, 5.58 MPa) and cylindrical (8.36 MPa, 4.81 MPa) specimens, with 20% and 25% porosities, respectively. The compressive strength was found to be low in air-dried samples and increased with higher water levels, peaking at the 40% water level. Furthermore, the porosity exhibited a significant correlation with the reduction in density, affecting the mechanical properties. For the cylindrical and cubical samples, the dry density decreased by 16.03 kg/m3 and 20.85 kg/m3 and the permeability increased by 0.41 mm/s and 0.84 mm/s, respectively, for every 1% increase in porosity. The results showcased the effect of water level variation on porous concrete properties as well as its promising ability to infiltrate water. This promotes the development of sustainable pavement systems by minimizing surface runoff and aiding groundwater recharge. [ABSTRACT FROM AUTHOR]

As an important hydrological ecosystem component, the glacier basin has great significance for climate and environment, and it is also linked to regional water sustainability. In this paper, the sampling and isotope analysis of glacial ice, ice-melt water, river water (river midstream and river downstream), groundwater (spring), and precipitation were carried out in a hydrological year of the Mingyong Glacier basin, which is located at the Meili Snow Mountains, Southeastern Tibetan Plateau. At the same time, the hydrograph separation of the recharge sources of the lower mountain pass is studied. The results show that the range of δD, δ18O, and d-excess (deuterium excess) in natural water bodies are significantly different, and the precipitation is the most obvious. The high values of δD and δ18O in the water samples all appeared in spring and summer, and the low values appeared in autumn and winter, while glacial ice showed opposite trends. Meanwhile, the local meteoric water line (LMWL) of the Mingyong Glacier basin is δD = 8.04δ18O + 13.06. The End-Member Mixing Analysis (EMMA) was adopted to determine the sources proportion of river water (river downstream) according to the δD, δ18O, and d-excess ratio relationships. The results showed that the proportion of ice-melt water, groundwater, and precipitation in the ablation period was 80.6%, 17.2%, and 2.2% as well as 19.2%, 73.1%, and 7.7% in the accumulation period, respectively. Ice-melt water has a higher conversion recharge rate to groundwater and indirectly recharges river water, especially in nonmonsoon seasons. In other words, the main recharge source of river water in the lower reaches of the Mingyong Glacier basin during the ablation period is ice-melt water. In the accumulation period, the main recharge source of river water in the lower reaches of the Mingyong Glacier basin is groundwater, while nearly half of the recharge of groundwater comes from ice-melt water. Therefore, regardless of the ablation period or the accumulation period, ice-melt water is sustainable and important to this region. [ABSTRACT FROM AUTHOR]

The components of water balance (WBC) that involve precipitation, evapotranspiration, runoff, irrigation, and groundwater recharge are critical for understanding the hydrological cycle and water management of resources in semi-arid and arid areas. This paper assesses temporal and spatial distributions of surface runoff, actual evapotranspiration, and groundwater recharge upstream of the New Assiut Barrage (NAB) in the Nile Valley, Upper Egypt, using the WetSpass-M model for the period 2012–2020. Moreover, this study evaluates the effect of land cover/land use (LULC) alterations in the study period on the WBC of the NAB. The data provided as input for the WetSpass-M model in the structure of raster maps using the Arc-GIS tool. Monthly meteorological factors (e.g., temperature, rainfall, and wind speed), a digital elevation model (DEM), slope, land cover, irrigation cover, a soil map, and depth to groundwater are included. The long-term temporal and spatial mean monthly irrigation and precipitation (127 mm) is distributed as 49% (62 mm) actual evapotranspiration, 15% (19 mm) groundwater recharge, and 36% (46 mm) surface runoff. The replacement of cropland by built-up areas was recognized as the primary factor responsible for the major decrease in groundwater, an increase in evapotranspiration and an increase in surface runoff between LCLU in 2012 and 2020. The integration of the WetSpass model with GIS has shown its effectiveness as a powerful approach for assessing WBC. Results were more accurate and reliable when hydrological modeling and spatial analysis were combined. The results of this research can help make well-informed decisions about land use planning and sustainable management of water resources in the upstream area of the NAB. [ABSTRACT FROM AUTHOR]

Recognizing how human activities affect hydrological systems is vital for the sustainable preservation and effective management of water resources in the watershed. Hence, this paper focuses on the hydrological response to land use and land cover (LULC) change scenarios in the Anyang watershed, South Korea. We obtained LULC data maps for the years 2000, 2013, and 2022 from the local government, revealing significant changes over the years. Agricultural lands experienced a 6.2% increase from 2000 to 2022, and pastureland expanded by 8.67% over two decades. The SWAT model was utilized to assess the impact of LULC on the hydrological components of the study watershed. Model calibration and validation for each LULC change were carried out using the SWAT-CUP program, considering the recorded streamflow information of the region. An excellent agreement was reached between the simulated and measured streamflow in both the calibration and validation stages under various LULC conditions. The Nash–Sutcliffe model efficiency (NSE), the objective function, demonstrated values of 0.9, 0.89, and 0.89 during the calibration for 2000, 2013, and 2022, respectively, in the LULC scenario, while for the validation, we obtained values of 0.82, 0.78, and 0.80 for 2000, 2013, and 2022, respectively. Our findings indicate that the surface runoff rise contributed much to the water yield increase over the two decades compared to the other components in terms of the water yield, while the contribution of evapotranspiration (ET) to the watershed hydrological cycle declined by 1.66% from 2000 to 2022. The southeastern sub-basin part showed a high groundwater recharge distribution due to agricultural land, rice area, and forest area changes. [ABSTRACT FROM AUTHOR]

Climate change will lead to prolonged droughts in various regions of the world, which may significantly affect agricultural production. This is particularly problematic for soils with low water retention capacity, which cannot store sufficient water for crops. In this paper, we investigate how a change in the water‐holding capacity of the soil material, as could be achieved by increasing the soil organic carbon (SOC) amount, affects the components of the soil water balance (evaporation, transpiration, and groundwater recharge). Specifically, we state the hypothesis that an increased water‐holding capacity in a shallow soil layer, as it is achieved through SOC enrichment at the soil surface, will result in more water being stored near the soil surface and lost to unproductive evaporation, thereby reducing the amount of water available to plants and groundwater recharge. The hypothesis was tested by numerical simulations, employing the Hydrus‐1D program package to model the water balance in a soil–plant–atmosphere system for an arable crop in hydrologically contrasting years. The study considered soils with varying textures and different depths of a soil layer with increased SOC content. The soil hydraulic properties (SHP) of the soil material, including the effect of SOC on the SHP, were determined using a recently developed pedotransfer model based on data from over 500 samples. We showed that both the improved water retention by SOC and its vertical distribution affect the soil water balance in a complex manner. In sandy soils, increasing the water‐holding capacity in shallow layers up to 0.1 m led to enhanced evaporation and thus a decrease in water availability for crops. However, deeper incorporated SOC could ameliorate these negative effects. Our findings suggest that not only the amount but also the vertical SOC distribution should be considered if enrichment of SOC shall be applied to mitigate the effect of droughts. Core Ideas: Addition of soil organic carbon (SOC) alters soil material's hydraulic properties.This, in turn, impacts the water balance of soils under agricultural use.The depth at which SOC is incorporated into soils plays a crucial role in the partitioning of evapotranspiration (ET) into evaporation (E) and transpiration (T).Deeper incorporation of SOC results in greater water availability for plants. [ABSTRACT FROM AUTHOR]

Mining and quarrying provide the basic raw materials for sustaining human well-being and are critical for achieving economic developments. At the same time, environmental degradation and its associated social impacts and inequalities have become a grave reality of mining sector that affects all nations, individually and/or collectively. Assessment of the environmental impacts arising from mining and quarrying is critical to limit the environmental problems within the barest minimum levels. Although many impact assessment studies are available on mining/quarrying of different major and minor minerals, not many studies exist on quarrying for laterite blocks which is being widespread in many of the fast developing tropical and sub-tropical regions of the world like India. Therefore, this paper evaluates the impact of laterite quarrying for construction blocks, in one of the twin river basins in SW India, the Netravati–Gurpur river basin, where the activity is widespread. The Rapid Impact Assessment Matrix (RIAM) method was used to evaluate the impacts of laterite quarrying as it allows a comprehensive analysis of the results based on the individual environmental score obtained for each component. RIAM is a valuable assessment tool, owing to its capability in quick, collective and reliable evaluation of the impacts that can aid decision making and minimization of environmental impacts, especially at early planning stages. Data pertaining to resource extraction, identification of impacting actions, mapping of mining hotspots, etc., were collected from primary and secondary sources through systematic field work and sample collection, questionnaire surveys within the local community and other stakeholders such as mine operators, labourers, officials of Government departments, etc. A total of 21 laterite quarries are located in the basin with a total production of 5.7 million laterite bricks/year (0.115 × 106 ty−1). The impact assessment study revealed that the activity not only disturbs the natural environment especially, hydrology, air quality and noise levels, ecology, land use and soil stability but has profound influence on the socio-economic factors of human health and immunity, displacement, etc., of the quarrying-hit areas. The activity also recorded both long-term and short-term positive impacts as a source of employment and income generation. Additionally, the activity favours groundwater replenishment and agriculture productivity of the area where appropriate mine closure measures were taken up. However, the positive impacts of the activity are far outweighed by the fact that most impacts of laterite quarrying are of class − C (moderate negative impact) and − D (significant negative impact) owing to the long-term socio-environmental and bio-ecological implications of the activity. Thus, it is imperative that there is significant improvement in policy and regulatory framework and its implementation for mining and quarrying of building materials which is vital for meeting future development requirements. [ABSTRACT FROM AUTHOR]

Parameter sensitivity analysis plays a critical role in efficiently determining main parameters, enhancing the effectiveness of the estimation of parameters and uncertainty quantification in hydrologic modeling. In this paper, we demonstrate an uncertainty and sensitivity analysis technique for the holistic Soil and Water Assessment Tool (SWAT +) model coupled with new gwflow module, spatially distributed, physically based groundwater flow modeling. The main calculated groundwater inflows and outflows include boundary exchange, pumping, saturation excess flow, groundwater–surface water exchange, recharge, groundwater–lake exchange and tile drainage outflow. We present the method for four watersheds located in different areas of the United States for 16 years (2000–2015), emphasizing regions of extensive tile drainage (Winnebago River, Minnesota, Iowa), intensive surface–groundwater interactions (Nanticoke River, Delaware, Maryland), groundwater pumping for irrigation (Cache River, Missouri, Arkansas) and mountain snowmelt (Arkansas Headwaters, Colorado). The main parameters of the coupled SWAT + gwflow model are estimated utilizing the parameter estimation software PEST. The monthly streamflow of holistic SWAT + gwflow is evaluated based on the Nash–Sutcliffe efficiency index (NSE), percentage bias (PBIAS), determination coefficient (R2) and Kling–Gupta efficiency coefficient (KGE), whereas groundwater head is evaluated using mean absolute error (MAE). The Morris method is employed to identify the key parameters influencing hydrological fluxes. Furthermore, the iterative ensemble smoother (iES) is utilized as a technique for uncertainty quantification (UQ) and parameter estimation (PE) and to decrease the computational cost owing to the large number of parameters. Depending on the watershed, key identified selected parameters include aquifer specific yield, aquifer hydraulic conductivity, recharge delay, streambed thickness, streambed hydraulic conductivity, area of groundwater inflow to tile, depth of tiles below ground surface, hydraulic conductivity of the drain perimeter, river depth (for groundwater flow processes), runoff curve number (for surface runoff processes), plant uptake compensation factor, soil evaporation compensation factor (for potential and actual evapotranspiration processes), soil available water capacity and percolation coefficient (for soil water processes). The presence of gwflow parameters permits the recognition of all key parameters in the surface and/or subsurface flow processes, with results substantially differing if the base SWAT + models are utilized. [ABSTRACT FROM AUTHOR]

Pakistan is currently facing physical and economic water scarcity issues, which have been further complicated by the rapid increase in its population and climate change. In affected areas, many methods are being used to tackle this problem, among which rainwater harvesting (RWH) provides the best alternative source of domestic water supply. In rainwater harvesting, a mechanism is designed to effectively collect surface runoff during rainfall events from residential rooftops. It has also been found that rainwater has great potential as a source of water supply in residential areas of major cities, such as Lahore, which is the focus of our study. This research paper examines rainwater harvesting as a sustainable solution to address the challenges of drinking water scarcity and urban flooding. The study discusses the benefits of rainwater harvesting, including reducing reliance on municipal water sources, improving water quality, and mitigating the impact of urban flooding. Additionally, the paper explores the use of filtered water points in conjunction with rainwater harvesting systems to provide clean drinking water to communities. The research draws on case studies from various regions to illustrate the effectiveness of rainwater harvesting as a sustainable solution to water scarcity and urban flooding. Ultimately, the study concludes that rainwater harvesting, when coupled with filtered water points, can offer an effective and sustainable solution to address drinking water scarcity and urban flooding. [ABSTRACT FROM AUTHOR]

2 Sahin Y, Tayfur G. 3D modelling of surface spreading and underground dam groundwater recharge: Egri Creek Subbasin, Turkey. The study of Peksezer ([1]) was the first one, which had investigated the use of the artificial recharge of groundwater by the surface recharge basins, and the underground dam for the Egri Creek Subbasin. [Extracted from the article]

Land-use/land-cover (LULC) change is considered a key human factor influencing groundwater recharge in floodplains. Without accurate estimations, the impact of LULC change on water balance components may be either significantly understated or exaggerated. This paper assesses the impacts of LULC changes from 1990 to 2018 on water balance components and groundwater levels of the Drava floodplain, Hungary, where human interference has led to a critical environmental situation. In this study, a spatially-distributed water balance model (WetSpass-M), and a groundwater flow model (MODFLOW-NWT) were integrated to assess the impacts of LULC changes. The moderate expansion of built-up areas increased surface runoff, while the afforestation of arable land and meadows and the overgrowth of bare mudflats with willow shrubs increased evapotranspiration. As a consequence, total annual groundwater recharge decreased by 5.3 × 107 m3 in the floodplain with an average of 335 mm year−1 and 317 mm year−1 in 2012 and 2018, respectively. Moreover, an average groundwater level decline by 0.1 m is observed in the same period. Declined groundwater recharge, increased runoff, and evapotranspiration exerted a negative effect on water resources in the Drava basin. The approach tested in this paper allows temporal and spatial estimation of hydrological components under the changes of LULC, providing quantitative information for decision-makers and stakeholders to implement efficient and sustainable management of water resources in the Drava floodplain. The provided integrated model is also applicable to regionally. [ABSTRACT FROM AUTHOR]

In Central Africa, groundwater remains the least understood component of the water cycle. Isotopic techniques that are well known to be efficient in tracking the movement of water along its path have been applied for only three decades and can be summarized in a handful of case studies. This review aims to put together all the stable and radioactive isotopic data (>500 samples from rainfall, surface and groundwater) published in Cameroon to: (i) identify the drivers responsible for precipitation isotopes' spatial variation and climatological implications, (ii) elucidate the groundwater recharge mechanisms over the countries and relationships with rivers, and (iii) highlight the existence of paleo-groundwater in the country. It is found that rainfall stable isotope variation is linked to the migration of the Intertropical Convergence Zone (ITCZ): the groundwater recharge can be diffuse and focused. This latter mechanism is mainly observed in the semi-arid region. It is in this relatively dry region that most of the paleo-groundwater resources are identified thanks to 14C dating. This information will be useful to develop water management strategies regarding all the challenges (e.g., climatic and demographic) faced by the country. Finally, this paper discusses the gaps groundwater isotope hydrology can still fill for contributing to a sustainable development of the country. [ABSTRACT FROM AUTHOR]

Geographically isolated wetlands (GIWs) play a critical role in regional hydrology, streamflow, groundwater recharge, evapotranspiration, and water quality. Despite their importance, research on quantifying discharges from these wetlands remains scarce. This study focuses on the hydrological characterization of GIWs in W-C Florida, a region where they cover a significant proportion of the land surface. The paper introduces a new procedure for developing Stage–Storage–Discharge (rating) characteristics essential for deterministic hydrological modeling in larger geographic areas. The approach synthesizes and extends previous research methodologies and offers simplified key modeling coefficients (m and n), which act as intelligent calibration knobs. These coefficients, when coupled with easily derivable physical attributes such as areas, slopes, and elevations, allow for the accurate simulation of downstream discharge timings and magnitudes, including flood behavior. The proposed method was tested using observational data from well-calibrated models. The results indicated a relative error of −7.2% for stage–storage and 15% for stage–discharge. GIS-based techniques were evaluated against surveyed data, and the results showed an accuracy of 0.16 m (0.52 ft) in estimating both the invert elevation and the maximum depth of GIWs. This effort will ultimately contribute to a better understanding and management of these critical ecosystems. [ABSTRACT FROM AUTHOR]

This study aims to illustrate and present various techniques for evaluating the performance of check-dams and proposes some suitable approaches for impact assessment of dams built in the Balochistan province of Pakistan. These dams were built during the last decade to overcome the challenges of water scarcity and depleting aquifers due to excessive Groundwater (GW) extraction. It was expected that these dams would recharge the GW resources and save the aquifer system from collapsing. Check-dams have traditionally been the permanent source of water within the province. A check-dam is used to delay the floodwater runoff to make it available for domestic and agriculture purposes or to recharge GW. The water along these dams permeates into the ground to keep the aquifer genuinely stable throughout the year. The data were collected based on studies of published research papers and reports of international organizations containing key characteristics of performance evaluation techniques. This review will help to evaluate procedures, policy, and governance interventions in Balochistan by comparing them with the adopted practices in other regions of the world and its impact on the well-being of the society. In this paper, the performance evaluation of check-dams for specific cases is presented. The knowledge acquired will be utilized to highlight state-of-the-art practices and to identify the need for further research in this field. [ABSTRACT FROM AUTHOR]

Global warming has had significant effects on the hydrological cycle. In North Africa, these effects have resulted in a continued decrease in the amount of annual precipitation, greatly influencing the availability of surface and groundwater resources. This paper aims to evaluate drought episodes in a long dataset from Djelfa (Algeria) using a statistical approach based on a decision support system enabled by the Hyfran-plus software, to fit the best statistical distribution model and predict non-exceedance probability of precipitation. The standardized precipitation index is used to highlight sequences of meteorological drought and changes in weather patterns. Shift in precipitation has been identified by Wilcoxon Test for homogeneity; Wold-Wolfowitz test of independence, Kendall's test of trend and new cumulative mean difference curve (CMD) developed to visualize the trend of the precipitation and runoff dataset, Autocorrelation function (ACF) and Fourier spectrum and Deuterium excess isotopes has been used to visualize trends. Log–log plot; the mean excess function (MEF), AIC and BIC criteria are used to select the best distribution fitting model. The statistical results obtained indicate that the dataset follows a heavy-tailed distribution (Pearson type III), Values of excess Deuterium indicate that groundwater recharge has occurred in cold weather different from the actual period. SPI analysis shows that dry years cover more than 51% compared to 49% of wet years. The CMD curve shows a change and trend in the precipitation and runoff time series since 1974. Forecasts show drought recurrences to be between 3 and 200 years. [ABSTRACT FROM AUTHOR]

In such areas, the significant increases in sea level and atmospheric temperatures due to climate change could exacerbate water resources salinization. All over the Earth, more and more studies have shown the effects of climate changes generated by anthropic release of greenhouse gasses on the hydrological cycle [[1]]. The already increased demand of freshwater triggered by climate change and the consequent land use changes, has intensified the research on water resources salinization and the feasible techniques aimed at mitigating such effects, such as for example the wastewater reuse via managed aquifer recharge systems [[10]]. The third paper published in this Special Issue provided a background to the salinity issue in the Murray-Darling Basin (Australia), then reviewed the salinity management strategies, the various actions that have been implemented through these strategies to control salinity, and the role of the recent Basin Plan in salinity management [[15]]. [Extracted from the article]

The arid endorheic basin of northwest China is characterized by rich land resources, water shortage, and a fragile ecological environment. The establishment of a credible coupling model of groundwater and surface water based on multi-source observation data is an effective means to study the change in basin water cycles and the sustainable utilization of water resources in the past and future. Based on the latest understanding of hydrogeological conditions, hydrology and water resource utilization data in the middle reaches of the Heihe River Basin (HRB), this paper constructs an up-to-date coupling model of surface water and groundwater to study the water balance change of the basin. The water resources data series under historical replay and CMIP5 climate model prediction are constructed to predict future changes in water resources. The study shows that, under the joint influence of natural conditions and human activities, the average annual recharge of groundwater in the study area from 1990 to 2020 is 17.98 × 108 m3/a, the average annual discharge is 18.62 × 108 m3/a, and the difference between recharge and discharge is −0.64 × 108 m3/a. The total groundwater storage is −19.99 × 108 m3, of which the groundwater storage from 1990 to 2001 was −17.52 × 108 m3 and from 2002 to 2020 was −2.47 × 108 m3. Abundant water from 2002 to 2020 in the basin significantly improved the loss of groundwater storage. Under the prediction of historical reappearance and the CMIP5 CNRM-CM5 model RCP4.5 and RCP8.5 pathways, the groundwater level of the Heihe River–Liyuanhe River inclined plain falls first because the HRB has just experienced a wet season and then rises according to future climate change. The groundwater level of the inclined plain east of the Heihe River and Yanchi basin decreases continuously because of the change in water cycle caused by human activities. The erosion accumulation plain is located in the groundwater discharge zone, and the water level is basically stable. Under the conditions of water resource development and utilization, the runoff of Zhengyixia hydrological station cannot meet the requirements of the "97 Water Dividing Plan" of the State Council in most years in the future, and the ecological and production water in the lower reaches of HRB cannot be effectively guaranteed. With the implementation of water-saving irrigation under the RCP4.5 and RCP8.5 scenarios, the runoff of Zhengyixia can meet the "97 Water Diversion Plan". It is suggested to further improve the level of agricultural water savings in the middle reaches of the HRB and control the reasonable scale of cultivated land in order to reduce water consumption in the middle reaches of the HRB and implement sustainable utilization of water resources in the HRB. [ABSTRACT FROM AUTHOR]

Climate change and anthropogenic development considerably influence groundwater resource distribution and conditions. Catchment basin groundwater recharge—discharge computation reliability is needed for effective groundwater management policy formulation and implementation and also for resolving environmental challenges in such a watershed. This paper compares groundwater recharge patterns between urbanized and nearly natural small catchment basins of Israel's Western Mountain Aquifer (WMA). The correlation between precipitation volumes and surface runoff shows that surface runoff volume constitutes 3–4% of the precipitation volume in the Natuf catchment and 1–2% in the Te'enim catchment. These assessments reflect the differences in the land use, outcrop lithology, topography and hydrodynamic properties of the WMA within the model basins. A groundwater recharge assessment based on water balance and water table fluctuation methods was performed for the mountainous karstic Te'enim and Natuf catchment basins for all the available data from 2000 to 2020. The water balance method provided reliable estimates. The groundwater recharge assessment considered land use classification and climate changes during this period. The average multiannual groundwater recharge values for the 2000–2021 period varied from 17.6 × 106–24.8 × 106 m3 to 24.5–29.2 × 106 m3 for the Te'enim and Natuf catchment basins, respectively. For the relatively dry period of the 2013/2014–2017/2018 hydrological years when detailed measurements of the surface runoff were available, the corresponding groundwater recharge volumes were 17.6 × 106 m3 and 24.5 × 106 m3. The corresponding local groundwater recharge coefficients constitute 0.46–0.57 for the mostly agricultural Te'enim basin and 0.29–0.32 for the urbanized Natuf basin. A significant difference in the groundwater recharge coefficients between the studied catchments is caused mostly by the differences in land use. It is suggested that applying such a groundwater recharge estimation for small hydrological sub-basins can improve one's understanding of the groundwater recharge distribution within a major basin, enabling the application of an accurate regional hydrogeological model that may be extrapolated to other similar regions. [ABSTRACT FROM AUTHOR]

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Over exploitation of groundwater in Changping District of Beijing city has caused serious land subsidence in the past decades. In recent years, the operation of the South-to-North Water Transfer Project has reduced the land subsidence rate. In this paper, Experimental tests are performed using the GDS Consolidation Testing System to characterize the compression and rebound of soils at depths of less than 100 m caused by groundwater withdrawal and recharge in Changping District. The results indicate that the compressible layers are the main contributors to land subsidence. The first compressible layer experiences greater deformation and more considerable hysteresis than the other compressible layers with the same decrease in the pore water pressure. Therefore, the exploitation of the adjacent aquifer should be controlled in the future. The deformation in the second and third compressible layers is a gradual and long-term process with little rebound; therefore, the subsidence should be seriously addressed when the groundwater in the two compressible layers is exploited on a large scale. In the same compressible layer, silty clay is more compressible and hysteretic than silt. For the same soil sample, the deformation rate decreases gradually as the pore water pressure decreases, whereas the creep deformation shows an overall increasing trend. A parameter named the subsidence index Cw is proposed in this paper to describe the soil compressibility during groundwater withdrawal. All the soil samples are characterized by elastic-plastic deformation, and the shallow soil samples with less pore water pressure decrease are more likely to rebound. [ABSTRACT FROM AUTHOR]

Groundwater is one of the main resources for social-ecological systems. As part of the total water cycle and deeply connected with land use, groundwater management faces many challenges, especially in coastal areas. Landscape Scale Planning is an emerging approach for land use planning providing a framework for management based on evidence, given that landscapes have physical and information flows. Landscape Scale Planning embraces the following three dimensions: (i) the spatial dimension centres on the recognition of distinct landscape units; (ii) the temporal dimension entails past, current and future uses of a landscape; and (iii) the modification dimension involves the anthropogenic alterations that affected and will affect the landscape and its features along the spatial and temporal dimensions. Through a systematic literature review of 28 selected publications, this paper explores how groundwater management can be improved through a Landscape Scale Planning approach. The results show that Landscape Scale Planning can be applied as an integrative framework for groundwater management. Landscape units based on, but not limited to, geology, topography, cultural and socio-economic aspects can aid groundwater management to consider the differing spatial and temporal characteristics of the aquifer. Landscape Scale Planning can also favour the inclusion of land use change dynamics in groundwater management processes. To this end, the paper proposes guidelines for applying Landscape Scale Planning to inform groundwater management and consider land use changes. [ABSTRACT FROM AUTHOR]

The systematic assessment of spatial and temporal distribution of groundwater recharge (GWR) is crucial for the sustainable management of the water resources systems, especially in large-scale river basins. This helps in identifying critical zones in which GWR largely varies and thus leads to negative consequences. However, such analyses might not be possible when the models require detailed hydro-climate and hydrogeological data in data-scarce regions. Hence, this calls for alternate suitable modeling approaches that are applicable with the limited data and, however, includes the detailed assessment of the spatial–temporal distribution of different water balance components especially the GWR component. This paper aimed at investigating the spatial and temporal distribution of the GWR at monthly, seasonal and annual scales using the WetSpass-M physically distributed hydrological model, which is not requiring the detailed catchment information. In addition, the study conducted the sensitivity analysis of model parameters to assess the significant variation of GWR. The large-scale river basins such as the Omo river basin, Ethiopia, were chosen to demonstrate the potential of the WetSpass-M model under limited data conditions. From the modeling results, it was found that the maximum average monthly GWR of 13.4 mm occurs in July. The estimated average seasonal GWR is 32.5 mm/yr and 47.6 mm/yr in the summer and winter seasons, respectively. Further, it was found that GWR is highly sensitive to the parameter such as average rainfall intensity factor. [ABSTRACT FROM AUTHOR]

Ethiopia, marked by diverse geography and rapid land use/land cover (LULC) changes, grapples with formidable water resource management challenges. Understanding the hydrological response to these changes is paramount for sustainability. This review paper provides an overview of studies that investigated the hydrological impacts of LULC changes in Ethiopian basins. The review discusses methodologies, key findings, implications for sustainable land and water resource management, research gaps, and future directions. Emphasizing results from diverse studies that utilized hydrological and geospatial modelling, LULC significantly affects surface runoff, streamflow patterns, and groundwater recharge. The observed consequences are increased surface runoff, modified streamflow timing, and reduced groundwater recharge. The review underscores the urgency for integrated land and water management strategies to alleviate adverse effects. Future research priorities include basin-specific studies, long-term monitoring, integrated modelling, consideration of socio-economic factors, and incorporating climate change scenarios to enhance understanding and guide sustainable water resource management in Ethiopian basins. [ABSTRACT FROM AUTHOR]

Groundwater is an important resource for a multitude of purposes, and change in groundwater levels is an important factor in determining the increase and decrease of groundwater quantity in aquifers. This study has been carried out for Gomti River basin, where groundwater is the major drinking water source for the entire region. This paper evaluates the behavior of the groundwater levels using Visual MODFLOW under RCP 4.5 and RCP 8.5 scenarios. For modeling of groundwater flow, the entire study area was discretized into 108480 (X-direction) and 207090 (Y-direction) gridal network with each cell size of 1000 m × 1000 m. The model was calibrated for the period 2002 to 2008 and validated for the period 2009 to 2013 using data of 24 observation wells. During the calibration period of Visual MODFLOW, residual mean ranged between 0.658 and 0.268 m, and absolute residual mean ranged between 2.035 and 2.174 m. The calibrated Visual MODFLOW model was employed to evaluate the influence of climate change on future groundwater levels. Future groundwater recharge (2020–2030), obtained after the application of four (MIROC-ESM, MIROC-ESM-CHEM, MIROC MIROC5, and MOHC-HADGEM2-ES) global climate model (GCM) data into prior SWAT model, was applied to Visual MODFLOW. After applying, the projected future (2020–2030) trend in the groundwater levels was found continuously decreasing due to low groundwater recharge and excessive groundwater withdrawal in the basin in future. [ABSTRACT FROM AUTHOR]

In rice areas with shallow aquifers, an evaluation of alternative irrigation strategies should include the interactions between irrigation and groundwater recharge and reuse, which influence the overall irrigation efficiency. A modelling system composed of three sub-models within a MATLAB framework (a physically based, semi-distributed agro-hydrological model and two empirical models, the former for the channel network percolation and the latter for the groundwater level) was applied to a 1000 ha rice district in the Padana Plain, Italy. The calibrated framework estimates the daily time series of the water supply needed and of the groundwater level for a given irrigation management, based on the inputs provided (agro-meteorology, crop data, soil data, irrigation practices, groundwater table depth upstream of the study area). Five irrigation management strategies, relevant to the area, were compared: (i) wet seeding and continuous flooding (WFL), (ii) wet seeding and alternate wetting and drying (AWD), (iii) dry seeding and delayed flooding (DFL), (iv) dry seeding and fixed-turn irrigation FTI), (v) early dry seeding and delayed flooding (DFLearly). Due to economic advantages, dry-seeded techniques (DFL, FTI) are replacing the traditional WFL in northern Italy. Simulations show that dry seeding leads to a drastic decrease of the water table in April/May, reducing the overall irrigation efficiency of the area, and that DFL (widely adopted in the area) also causes a spike in rice irrigation needs in June when other crops increase their water demand, exposing the area to water scarcity. All the cited management strategies are assessed in the paper and AWD turned out to couple smaller irrigation needs (from June onwards) compared to continuous flooding techniques with a maintenance of the groundwater recharge, especially in the first part of the irrigation season, thus being a recommendable rice management alternative for the study area. [ABSTRACT FROM AUTHOR]

Protecting groundwater from contamination is today's most current environmental protection topic. What can man do in his environment to reduce the harmful impact of contamination on the environment, and thus the immediate effect on groundwater? Agricultural production is an ongoing source of groundwater contamination due to the increasingly frequent use of nitrates in fertilizers, which are washed out from the soil into groundwater due to precipitation. This paper investigates three wellfields in the north of the Republic of Croatia near the town of Varaždin. With the application of the RAPS method, the dependence of nitrate concentration in groundwater on the amount of precipitation was established. The analysis results show the connection of the observed parameters, especially in the upper aquifer layer. In this layer, the coefficients of correlation are greater than 0.80 at all locations, which shows a strong positive connection between the parameters. In the lower aquifer, the values of the coefficients of correlation are lower, and the results mostly indicate a weak correlation. The obtained results will serve as a starting point for future studies, which will aim to precisely determine the factors that influence groundwater quality in the observed area. [ABSTRACT FROM AUTHOR]

This paper details the development and evaluation of the enhanced future FLows and Groundwater (eFLaG) dataset of nationally consistent hydrological projections for the UK, based on the latest UK Climate Projections (UKCP18). The projections are derived from a range of hydrological models. For river flows, multiple models (Grid-to-Grid, PDM (Probability Distributed Model) and GR (Génie Rural; both four- and six-parameter versions, GR4J and GR6J)) are used to provide an indication of hydrological model uncertainty. For groundwater, two models are used, a groundwater level model (AquiMod) and a groundwater recharge model (ZOODRM: zooming object-oriented distributed-recharge model). A 12-member ensemble of transient projections of present and future (up to 2080) daily river flows, groundwater levels and groundwater recharge was produced using bias-corrected data from the UKCP18 regional (12 km) climate ensemble. Projections are provided for 200 river catchments, 54 groundwater level boreholes and 558 groundwater bodies, all sampling across the diverse hydrological and geological conditions of the UK. An evaluation was carried out to appraise the quality of hydrological model simulations against observations and also to appraise the reliability of hydrological models driven by the regional climate model (RCM) ensemble in terms of their capacity to reproduce hydrological regimes in the current period. The dataset was originally conceived as a prototype climate service for drought planning for the UK water sector and so has been developed with drought, low river flow and low groundwater level applications as the primary objectives. The evaluation metrics show that river flows and groundwater levels are, for the majority of catchments and boreholes, well simulated across the flow and level regime, meaning that the eFLaG dataset could be applied to a wider range of water resources research and management contexts, pending a full evaluation for the designated purpose. Only a single climate model and one emissions scenario are used, so any applications should ideally contextualise the outcomes with other climate model–scenario combinations. The dataset can be accessed in Hannaford et al. (2022): 10.5285/1bb90673-ad37-4679-90b9-0126109639a9. [ABSTRACT FROM AUTHOR]

The interaction between surface water and groundwater is a significant topic in groundwater-related problems. This study suggests an exact model based on Laplace transformation to calculate the groundwater flow in river-aquifer systems. Exact models play an important role in simulating the future behavior of river-aquifer systems. Therefore, investigation of the exact models for river-aquifer systems is a hot topic in the hydraulics of groundwater flow modeling. The objective of this research is to present new exact models for simulating the hydraulics of groundwater flow in river-aquifer systems with a more general function of river level variation under recharge by means of Laplace transform method. A general function is adopted to describe the river level variation, in which some situations such as linear, exponential and power of time variations in the river level can be treated as special cases. The effects of variations in aquifer parameters on groundwater hydraulic head are evaluated. It is shown that the groundwater hydraulic head grows slower in aquifers with a greater thickness or hydraulic conductivity. In addition, the effect of changes in specific storage is too little on the groundwater hydraulic head. The variations in hydraulic heads due to changes in recharge rate with different values of thickness, hydraulic conductivity, specific storage, and length are analyzed. It is observed that the groundwater hydraulic head in an aquifer with a lesser length, higher hydraulic conductivity or higher thickness is less sensitive to a change in the recharge rate than in an aquifer with a higher length, lesser hydraulic conductivity or lesser thickness. Furthermore, it is shown that the differences in hydraulic heads due to the increase in recharge rate are not significant for different values of specific storage. The results of the present new exact models are successfully verified by the results obtained from the analytical solution of Bansal and Das. Also, for more reliability, the results are compared with those results of MODFLOW. The results show that the presented new exact models are accurate, robust and efficient. One of the advantages of the solutions is to investigate the sensitivity analysis of aquifer parameters, which has been carried out in this paper. Furthermore, in the present research a more general function describing river level variation is considered, in which the linear, exponential and power of time variations are special cases. [ABSTRACT FROM AUTHOR]