Sustainable Management Of Groundwater Resources Research Articles

Assessment of hydrochemical shift in riverine aquifers of the mid-Gangetic plain of Uttar Pradesh, India

The over-exploitation of groundwater resources in the agriculture-intensive middle Gangetic plains is leading to the depletion of the water table and deterioration of its quality. A total of 100 groundwater samples were collected from the mid-Gangetic plain, specifically from the Mirzapur and Pratapgarh districts of Uttar Pradesh, during two seasons: pre-monsoon (pre-M) and post-monsoon (post-M). Various indices and multivariate statistical analysis were employed to assess groundwater chemistry and suitability for different purposes, including the Water Quality Index (WQI), sodium adsorption ratio (SAR), soluble sodium percentage (SSP), residual sodium carbonate (RSC), and Permeability Index (PI). The findings revealed that HCO3−, NH4+, and PO43− exceeded permissible limits, while hardness, SO42−, Cl−, and SO42− remained within acceptable ranges. Analysis of variance (ANOVA) indicated significant variations (p < 0.05) in pH, electrical conductivity, total dissolved solids, NO3−, Ca2+, dissolved silica, NH4+, HCO3−, NO3−, and PO43−. Groundwater chemistry in the area is influenced by weathering and evaporation processes. In terms of drinking water quality, all analysed samples were found to be poor during the pre-monsoon season, with 68% of samples in Pratapgarh and 56% in Mirzapur showing poor quality during the post-monsoon season. SAR, SSP, RSC, and Na% values indicated water suitability for irrigation, with Magnesium Hazard (MH) and Permeability Index (PI) values suggesting unsuitability for irrigation purposes. Industrial indices such as Langelier Saturation Index (LSI) indicated slightly to non-corrosive water, while Ryznar Stability Index (RSI) indicated light to heavy and intolerable corrosiveness of groundwater in both districts. Consequently, the groundwater in the area was deemed unfit for drinking without treatment but suitable for irrigation. While Pratapgarh's groundwater could be used for industrial purposes, groundwater quality in Mirzapur would require treatment. The findings of this study can aid local stakeholders, government agencies, and water resources managers in the sustainable management of groundwater resources in the study area.

Design of preliminary groundwater monitoring networks for the coastal Tra Vinh province in Mekong Delta, Vietnam

Study RegionThe study region is the coastal Tra Vinh province located in Mekong Delta, Vietnam Study FocusThe objective of the study is to design preliminary monitoring networks for groundwater level and salinity monitoring in the three heavily abstracted aquifers in the Tra Vinh province. Since data from the existing monitoring were insufficient to explore variogram analysis and subsequent Kriging interpolation for the network design, groundwater flow and saltwater transport models were constructed to create groundwater level and salinity distributions. An iterative procedure was adopted to select monitoring well locations based on the contour maps of groundwater levels and total dissolved solids (TDS) constructed from the groundwater models. The standard deviation of Kriging interpolation error was used as the criteria to assess the quality of the designed monitoring networks. Priorities for the locating groundwater level monitoring wells were targeted in areas with cones of depression and boundaries, while priorities for salinity monitoring were given to coastal zone and inland fresh/saltwater interfaces. New Hydrological Insights for the RegionGroundwater overexploitation has resulted in storage depletion and saltwater intrusion in the Tra Vinh province. Simulations from the numerical models determined the cones of the depression and predicted intrusion from inland saltwater trapped in clays from past marine transgressions and from seawater in the coastal zone. A limited number of monitoring wells is operated and is insufficient to delineate the cone of depression and fresh/salt water interfaces. This study combined the numerical model simulation results and Kriging interpolation method and designed preliminary groundwater level and salinity monitoring networks for the Tra Vinh province. Once the designed networks are implemented, observed data from the networks will provide valuable information for sustainable groundwater resources management in Tra Vinh province. Data availabilityAll data generated or analyzed during this study are available upon request from the corresponding author.

The use of stable isotopes to identify surface water–groundwater interaction in the Kruger National Park, South Africa

The role of groundwater, in general, is often overlooked in freshwater ecosystem management policies and in the management of South Africa’s flagship conservation area, the Kruger National Park (KNP). To address this gap, a generalised conceptual model of surface water–ground water (sw–gw) interactions in the southern and central regions of the KNP was developed. To do this, stable isotope ratios (d18O and d2H) of groundwater, rainfall and surface water were used to determine the extent to which the base flow of perennial, seasonal and ephemeral streams on different geologies (granite vs. basalt) is driven by rainfall or groundwater. These results show that the δ18O and δ2H ratios of perennial rivers are similar to that of groundwater, while seasonal and ephemeral rivers on basalts have values closer to rainfall. On granite substrates, however, the isotope ratios of the seasonal and ephemeral rivers have values closer to groundwater than rainfall. The larger seasonal Mbyamiti River had similar isotope ratios to that of groundwater, and the highly ephemeral Nwaswitsontso had episodic interaction with groundwater (i.e. isotopic ratios overlap occasionally). These results show that decisions necessary for the sustainable management of groundwater resources are better informed when the natural interaction, movement, and exchange between groundwater and rivers are understood. This has particular relevance for large conservation areas in southern Africa that are expected to experience more variable climates in the future with both increases in drought and rainfall intensities.

Exploration and Sustainable Management of Groundwater Resources in Geologically Complex Terrain

Groundwater is a precious and limited resource [...]

Geochemical evidence for annual variability of fluoride levels in deep groundwater on land subsidence plain in Cangzhou, Hebei Province, China

Ecological water supplementation effectively controls the land subsidence rate and protects the groundwater environment. However, the annual variability and evolutionary mechanisms of F− concentration in deep groundwater during ecological water supplementation are poorly understood. In total, 92 deep groundwater samples from 2012 to 2021 were collected and analyzed in the Cangzhou land subsidence area. The results show that the range of F− concentrations in deep groundwater was 0.10–7.83 mg/L during 2012–2021, with 44.08 % of samples exceeding China's national standards (1.00 mg/L) for drinking water. The F− concentration in deep groundwater increased steadily during 2012–2017 and exhibited a notable decrease during 2018–2021. Halite dissolution was more effective after ecological water supplementation, inducing a decrease in F− concentration by dilution effect in deep groundwater. Meanwhile, stronger cation exchange facilitated F− desorption into the deep groundwater after ecological water supplementation. This research will aid in improving our understanding of the influence of ecological water supplementation on groundwater quality and provide new insights for the sustainable management of deep groundwater resources.

Rainwater Harvesting through Point Recharge Method for Efficient Recharge of Tube Wells for Sustainable Management of Groundwater Resources in Karnataka

Water is a precious natural resource for sustaining life, agriculture and environment. The dependability on groundwater has reached high in all time in recent decades due to reasons such as unreliable supplies from surface water due to vagaries of monsoon, increase in demand for domestic, agricultural and other purposes. Karnataka is largely dependent on groundwater to meet industrial, municipal, domestic and irrigation needs. So, Rainwater harvesting (RWH) forms an important component for development and management of water resources for domestic, agricultural, municipal and industrial uses. Management of scanty rain fall by rain water harvesting, Augmentation of depleting natural resources of water (deeper ground water table) and Management of poor-quality ground water and scope for conjunctive/domestic use is need of the hour. With increase in withdrawal of ground water, ground water (GW) table is declining at a rapid pace with an urgent need to recharge GW in addition to dilute poor quality ground water. Double ring technique of Groundwater Recharge consists of filtering the water at different layers using gradation materials generally the pebbles of different size with synthetic material wrapped around the casing pipe. By harvesting rain water and recharging into point recharge soaking infiltration gallery established at Irrigation Water Management Research Centre, (IWMRC) Belavatagi Tq: Navalagund has shown encouraging results as far as water quality, discharge and water table are concerned. The results of assessment of influence of ground water recharge through rainwater harvesting on ground water yield (lps), quality (dS/m) and fluctuations (feet bgl) during the year 2020, have shown that around 3.35 lakhs liters of water could be collected from rain water harvesting during the year 2020. Also, from point recharge through 7 recharge events (rain fall events from July to October 2020), it was observed that the considerable rise in the water table from more than 100 feet below ground level to around 22 feet below ground level, drastic reduction in groundwater salinity i.e. electrical conductivity (EC) of ground water from more than 10 dS/m to an average (EC) of 1.32 dS/m and tube well yield has significantly increased from 0.4 lps to around 2.4 lps. Therefore, Artificial recharge techniques through rainwater harvesting can be a better strategic approach to combat the emerging problems of water scarcity especially over exploitation of ground water and its quality deterioration.

Groundwater quality assessment for drinking purposes: a case study in the Mekong Delta, Vietnam

Groundwater serves as an important resource for people in the Mekong Delta, but its quality has been continuously declined from human activities. Current status of the groundwater quality needs to be evaluated for sustainable groundwater resource management. This study aimed to evaluate the groundwater quality for drinking purposes in the Mekong Delta, Vietnam, using multivariate statistical methods and integrated-weight water quality index. Data comprised 8 water quality parameters (pH, total hardness, nitrate (NO3−), iron (Fe), lead (Pb), mercury (Hg), arsenic (As), and coliforms) obtained from 64 observation wells in An Giang province, Dong Thap province, and Can Tho city, were analyzed by cluster analysis (CA), principal component analysis (PCA), and integrated-weight water quality index (IWQI). The results indicated that most parameters were within standards while excessive hardness and Fe contamination were found in some regions. More than 80% of samples were detected with serious coliform contamination. The CA results revealed that groundwater quality heavily depend on geological locations with 4 clusters of the sampling locations. Three principal components obtained from PCA could explain 77.2% of the groundwater quality variation. The IWQI values ranging from 4 to 2761 classified groundwater quality as excellent (53.1%), good (25%), poor (9.4%), very poor (4.7%), and undrinkable (7.8%), which were associated with coliform contamination. These findings have provided insights into the groundwater quality status in the region, which can benefit in developing a water protection strategy.

Development of an integrated multi-objective approach to formulate optimal harvesting policies with the aim of sustainable management of groundwater resources: study area: Varamin Plain

Abstract In the present study, an integrated multi-objective simulation -optimization model was developed using a NSGA-II optimization algorithm and GMS simulation software with the aim of sustainable harvesting from the Varamin aquifer. For this purpose, the quantitative model of the aquifer was simulated. Based on the calibrated model and integrated with the optimization algorithm, a two-objective management model was developed to control the exponential drop in the groundwater level and ensure sustainable harvesting from the wells. Then, according to multi-criteria decision-making methods and the Borda aggregation method, the optimal harvesting scenario of wells in operation was analyzed. The results show that more than 69% of the wells in the study area have experienced a rise of up to 30 m in the groundwater level during a 1-year period. It indicates the relative improvement of the aquifer in the direction of restoring its saturated thickness. Also, the comparison of the results obtained from the optimal and existing conditions showed that by applying the proposed model, an average of 46.9% can be saved in the harvesting of groundwater resources. For this purpose, it is necessary to reduce the allowed amount of harvesting from wells in this area from 21 to 11 L/s.

A Bibliometric Analysis of Groundwater Access and Its Management: Making the Invisible Visible

The sustainable management of groundwater resources is required to avoid a water crisis. The current study focused on a bibliometric analysis of groundwater access and management to assess research progress. The study was based on data from Dimensions.ai generated using the search terms “Groundwater”, “access”, and “management” for the period from 1985 to 2022. A total of 534 documents were identified as relevant and retrieved in CSV format. The intellectual structure of the retrieved data was visualized and analyzed using VoS viewer software (version 1.6.18). The analysis showed that the field of earth sciences had the highest number of publications on groundwater access and management (358), followed by the environmental sciences (155). Most of the articles (267) were about Sustainable Development Goal 6, which focuses on ensuring access to clean water and sanitation. The co-authorship analysis for the countries indicated that the United States has the most impact and research, and all other countries have established clusters around it. The citation analysis of the organizations showed that the International Water Management Institute, Charles Sturt University, and Wageningen University and Research were the top three organizations in terms of total citations (825, 611, and 584, respectively), indicating the most effect. The citation analysis for the sources indicated that the “Water” journal had a greater impact on readers with respect to groundwater research. Numerous parties are involved in the groundwater investigation; hence, a broad multidisciplinary approach is required. Therefore, researchers should work together rather than alone to address the problem of sustainable groundwater management.

Geoelectrical, Hydrogeological and Hydrochemical Investigations of the University of Calabar Campus (SE Nigeria): Implications for sustainable groundwater development

The rapid increase in population and infrastructural development has triggered unplanned groundwater development leading to severe stress on groundwater couple with several unsuccessful boreholes or failure of existing in the University of Calabar, Calabar (Nigeria). Hence, an integrated hydrogeological study was undertaken in the university using vertical electrical sounding (VES), to delineate and characterise aquifers and assess the groundwater quality for drinking and irrigation uses, in addition to evolution and human health risk assessment. The results reveal two water bearing units. The first is composed of medium-coarse-gravelly sand with thickness and resistivity in the range 3.6–118.8 m and 540–3500 Ω m, while the second underlying the first aquifer is composed of clayey, fine-medium sand with resistivity and thickness values in the range 44–2200 Ω m and 50 - α. Aquifer parameters from VES and pumping tests showed average hydraulic conductivity (K) and transmissivity (T) of 180 m/day and 25,740 m2/day for the first aquifer and 180 m/day and 21,384 m2/day for the second aquifer. Regionally, the groundwater flow in the university occurs toward the south. Hydrochemical data show that all the physical parameters, major and minor ions, trace and rare earth elements are within the maximum acceptable limits for drinking and agricultural uses. The dominant hydrochemical facies are Na+-Ca2+-Cl--SO42-, Mg2+-Ca2+-HCO3--Cl- and Ca2+-Mg2+-HCO3--Cl- with silicate weathering, ion exchange and reverse ion exchange as the major processess controlling the groundwater chemistry. Health risk of water through oral (drinking) and dermal (bathing) pathways showed that values of hazard quotients (HQs) and hazard index (HI) of all the trace elements (Al, As, Cd, Co, cr, Cu, Fe, Mn, Ni, Pb, Zn) were less than one. This suggests that these elements does not pose any adverse risks to the local people through drinking and bathing, but children are more sensitive than adults. This study will serve as a guide for future sustainable development and management of groundwater resource in the university and its environs.

Geochemical characteristics and water quality assessment in the Mt. Changbai volcanic field, Northeastern China

The chemistry of groundwater is an important determinant of water quality, which is vital to human health and the ecosystem. It is estimated that 10% of the worldwide population lives in the vicinity of an active volcano; in these regions, the quality of the water could greatly affect crop yield and soil fertility. The Mt. Changbai volcanic field (CVF), located on the border between China and North Korea, is the most well-preserved typical forest ecosystem in eastern Asia, providing various ecological services to human beings. Many types of water bodies, including hot springs, cold springs, and surface water bodies (e.g. rivers and pools) are distributed in the volcanic field. In this study, the geochemical characteristics of these water types, the quality of the water for irrigation purposes, as well as the water quality-related natural mechanism of the water chemistry in the CVF were systematically studied. The results indicate that the hydrochemical characteristics of the water samples in the CVF show the obvious difference between the volcanic cone and the peripheral areas. Significant spatial variation in the water quality was found in the CVF, where water in the peripheral areas was found to be of better water quality than that in the volcanic cone. The hot spring water in the CVF is not only unsuitable for drinking, but also unsuitable for irrigation. Water-rock interactions, ion exchange, and the addition of magmatic volatiles as well as atmospheric and anthropogenic sources are the main source and controlling factors of ions in the water in the CVF. The results of this study can be used as a reference for the sustainable management of groundwater resources in dormant volcanoes.

Hydrochemical characteristics and quality assessment of groundwater in Guangxi coastal areas, China

Groundwater is a main source of water supply in Guangxi Province, China. The urbanization expansion and ocean dynamic may change the groundwater quality, which is an important issue due to its effects on human health. In this paper, the influence of seawater intrusion and anthropogenic activity on the Guangxi coastal aquatic environment was assessed by geochemical and multivariate statistical methods. The result indicated that the chemical composition of groundwater in the study area is obviously associated with seawater and the main groundwater types were Ca·Na–Cl, Ca·Na–HCO3, and Ca–HCO3·Cl. The groundwater evolution path from land to sea in Guangxi is Ca–HCO3 → Na·Mg–Cl. The origin of salts in the study area is mainly controlled by mineral weathering, the hydrogen and oxygen isotopes contents point to the aqueous source of atmospheric precipitation. According to the results of PCA, seawater intrusion and pollution caused by human activities play an increasingly important role in the evolution of groundwater characteristics. Seawater intrusion is the main factor for the increase of groundwater salinity in Guangxi, while domestic sewage, industrial waste, fertilizers, and pesticides may contribute to the nitrate pollution of groundwater, especially in Beihai. The degree of groundwater nitrate pollution is as follows: Fangchenggang < Qinzhou < Beihai, which is associated with the degree of urbanization in the coastal area. Finally, the results of the water quality index (WQI) assessment show that 82.8 % of the samples were classified as excellent, while there is still a need to be vigilant about groundwater pollution caused by seawater intrusion and groundwater pollution. The results will be valuable for sustainable groundwater resource management in Guangxi coastal zone.

Trend analysis of groundwater levels in the monitoring boreholes within basalt formations in Dak Lak province

Groundwater from the basalt formations is the main source for the irrigation domestic use in Dak Lak province. Groundwater levels are important information for sustainable management water resouces in the region. The evolution of Groundwater level in the basalt aquifer in Dak Lak province is analyzed and evaluated by using the statistical test method. The results of the Mann-Kendall test indicated that the annual groundwater level had downward trend at 6/8 monitoring holes. The reduction was approximately from 0.03 m/year to 0.1 m/year at boreholes LK71T, LK29T, and CB1-II with high reliability in statistics (p-value &lt; 10%). The downward trend also appeared at 6/8 observed boreholes in the rainy season (0.05÷0.2 m/year) and dry seasons (0.03÷0.15 m/year). Groundwater level changed, in this work, was interpreted and linked to precipitation data. Comparison with annual rainfall monitoring data during the period 2010÷2016 at three stations in the study area, the Pearson correlation coefficient showed that the changed in rainfall amount overtime govern the groundwater level in the study area. Specifically, the results have identified a close correlation between the groundwater level at the boreholes LK29T, C4a, LK71T, and LK75T with average rainfall in the dry season in the study area. The strong correlation continued to be maintained at 3/8 monitoring holes (C4a, LK29T, and LK75T) in rainy season. Mann-Kendall statistical method and Pearson correlation can be applied to analyze long-term Groundwater level changes for sustainable management and exploitation of groundwater resources.

SD-DSS model of sustainable groundwater resources management using the water-food-energy security Nexus in Alborz Province

Unbalanced development of Alborz Province in recent years has amplified groundwater security crisis as well as water stress. This study conducted dynamic decision support system modelling of sustainable groundwater resources management based on water-food-energy security nexus (WFESN-SD-DSS). Using the results, the scenarios were designed in three categories of solutions: 1- Groundwater resources security; 2- Groundwater resources security; and 3- Groundwater resources security. The WFEN-SD-DSS model findings implied that combined policies represented the best solution and these included: Aquifer artificial recharge of 10 million cubic meters per year; control of well water usage; exploitation and reuse of graywater to supply 10% of agricultural water; 10% development of irrigation efficiency using novel irrigation systems; 10% reduction of agricultural waste; 10% development of the performance of agricultural products by modifying seeds, conserving plants; 5% reduction of electrical energy dissipation in combined cycle power plants; and development of solar water pump systems in agriculture sector.

Combined geophysical methods to investigate seawater intrusion in the Souss-Massa coastal area, Morocco

Groundwater are strategic water resources for irrigation and drinking purposes in the Souss-Massa semi-arid region (Morocco). These resources have been threatened during the last decades by different factors such as drought, over-pumping and marine intrusion. The latter is responsible for the degradation of the groundwater quality along the coastal area, which is reducing its usability. Therefore, the localisation of the freshwater/saline water interface is essential for better sustainable management of groundwater resources in the area. The objective of the present study is to assess the temporal changes, the extent, and the depth of the seawater intrusion in the Souss-Massa coastal area. To fulfil this objective, two monitoring sites were equipped with water conductivity measurement devices (Subsurface Monitoring Device – SMD) to observe the temporal changes of the salinity at a local scale, as well as to support the interpretation of a transient electromagnetic (TEM) survey. This survey consisted of 83 TEM soundings, along thirteen profiles located perpendicularly to the ocean and the two rivers delineating the study area. The data from the SMD stations highlight the temporal changes of electrical conductivity (EC) with depth, clearly illustrating the freshwater/saltwater interface location in the central part of the study area (−35.55 m NGM at the Tifnit location, ca. 1 km from the coast). In addition, the results of the TEM measurements show that the marine intrusion is already advanced towards the land, over a maximum distance of 2500 m. Finally, some new monitoring sites have been proposed to improve the current monitoring network for seawater intrusion and assess whether mitigation solutions lead to a slower progression of the seawater intrusion. Decision-makers can use these results as a basis for the development and implementation of effective policies to ensure a sustainable and integrated water resources management in this region.

Groundwater Recharge Estimation in Upper Gelana Watershed, South-Western Main Ethiopian Rift Valley

Estimating the spatial and temporal patterns of groundwater recharge through integrated water balance modeling plays an important role in sustainable groundwater resource management. Such modeling effort is particularly essential for data-scarce regions, such as the Rift Valley Lake basin in the Basement Complex of Ethiopia, which has shallow aquifers, a proliferation of wells, and poor groundwater monitoring networks. A spatially distributed water balance model (WetSpass), along with GIS and remote sensing tools, was used for groundwater recharge estimation for its suitability and efficiency in data-scarce hydrogeological regions. The WetSpass model depicted a very good performance in simulating the groundwater recharge in the Upper Gelana watershed within the Rift Valley Lake basin. The water balance analysis revealed that about 7% of the mean annual rainfall is converted to groundwater recharge, and the remaining rainfall amounts are partitioned into surface runoff (19%) and evapotranspiration (75%). The model simulation outputs are also used to investigate the relative influences of biophysical driving factors on the water balance components. While the land use types had a greater influence on the actual evapotranspiration processes, the soil texture classes were the dominant factors in the surface runoff and groundwater recharge processes in the watershed. The groundwater recharge rates were found to be higher than 400 mm/yr in the central parts (Fisehagenent, Tore, and Gedeb) and lower than 165 mm/yr in the southern parts (Hageremariam) of the watershed. The areal proportions of the low, medium, and high recharging parts of the watershed are, respectively, estimated as 15%, 68%, and 17% of the watershed area. Therefore, the spatial and temporal patterns of groundwater recharge should be taken into consideration in developing a sustainable groundwater resources management plan for the Upper Gelana watershed. Managed aquifer recharge can be adopted in high and medium groundwater recharging parts of the watershed to capture stormwater runoff during the wet season to improve the groundwater supply during dry months. Furthermore, monthly groundwater withdrawals should be regulated according to the spatial and temporal patterns of the groundwater recharge in the watershed.

An overview of the methods for evaluating the resilience of groundwater systems

Currently, groundwater resources are under anthropogenic and natural pressures. Depending on various factors, aquifers have diverse responses toward stresses. Resilience is among the performance criteria determining the ability of an aquifer to withstand unfavorable circumstances and to recover to a steady state after a failure. Hence, making use of this concept in groundwater systems is of cruciality in sustainable groundwater resources management. The main objective of the current research is to provide an overview on the employed procedures and existing difficulties appertaining to the appraisal of groundwater resilience. To this end, 36 studies which have evaluated groundwater resilience were regarded. Results highlighted that not only a very limited literature has employed groundwater resilience, but there also exist multiple knowledge gaps and complications, including resilience dimension, data scarcity and inaccuracies. In terms of groundwater quality and saltwater intrusion much little research exist, i.e. 7 studies among 36 ones. Evaluating groundwater resilience quantitatively, 11 methods were distinguished, each of which with its own advantages and disadvantages which may be engaged depending on factors such as available data and type of aquifer. Finally, more groundwater resilience analyses must be conducted at different spatiotemporal scales in order to preserve aquifers for the future generations.In summary, followings may be regarded to evaluate groundwater resilience:•To begin with, it must be specified which aspect of the aquifer's resilience and toward which unsatisfactory condition is planned to be considered.•Provided that no groundwater modeling is intended to be conducted, the observation data may be analyzed, considering the current state, governing violations, and new steady state.•On condition that groundwater simulation is planned to be conducted, subsequent to model's calibration and verification, the response of the aquifer, as a resilience criterion, is determined.

Bayesian Model Averaging Ensemble Approach for Multi-Time-Ahead Groundwater Level Prediction Combining the GRACE, GLEAM, and GLDAS Data in Arid Areas

Accurate groundwater level (GWL) prediction is essential for the sustainable management of groundwater resources. However, the prediction of GWLs remains a challenge due to insufficient data and the complicated hydrogeological system. In this study, we investigated the ability of the Gravity Recovery and Climate Experiment (GRACE) satellite data, the Global Land Evaporation Amsterdam Model (GLEAM) data, the Global Land Data Assimilation System (GLDAS) data, and the publicly available meteorological data in 1-, 2-, and 3-month-ahead GWL prediction using three traditional machine learning models (extreme learning machine, ELM; support vector machine, SVR; and random forest, RF). Meanwhile, we further developed the Bayesian model averaging (BMA) by combining the ELM, SVR, and RF models to avoid the uncertainty of the single models and to improve the predicting accuracy. The validity of the forcing data and the BMA model were assessed for three GWL monitoring wells in the Zhangye Basin in Northwest China. The results indicated that the applied forcing data could be treated as validated inputs to predict the GWL up to 3 months ahead due to the achieved high accuracy of the machine learning models (NS &gt; 0.55). The BMA model could significantly improve the performance of the single machine learning models. Overall, the BMA model reduced the RMSE of the ELM, SVR, and RF models in the testing period by about 13.75%, 24.01%, and 17.69%, respectively; while it improved the NS by about 8.32%, 16.13%, and 9.67% for 1-, 2-, and 3-month-ahead GWL prediction, respectively. The uncertainty analysis results also verified the reliability of the BMA model in multi-time-ahead GWL predicting. This highlighted the efficiency of the satellite data, satellite-based data, and publicly available data as substitute inputs in machine-learning-based GWL prediction, particularly for areas with insufficient or missing data. Meanwhile, the BMA ensemble strategy can serve as a powerful and reliable approach in multi-time-ahead GWL prediction when risk-based decision making is needed or a lack of relevant hydrogeological data impedes the application of the physical models.

Integrated approach for the investigation of groundwater quality through hydrochemistry and water quality index (WQI)

Evaluation of groundwater quality and their controlling processes are very important for the sustainable utilization of groundwater in any region. In the present study, 100 groundwater samples were collected during pre-monsoon and post-monsoon 2019 from the tube well and public water supply wells in Mewat district, Haryana to investigate the water quality for drinking purposes and their controlling hydrogeochemical processes through an integrated approach. Different methods like conventional hydrogeochemical analysis, ion ratio plots, and water quality index (WQI) were applied. The results showed that the groundwater of Mewat is highly saline, with the average concentration of total dissolved solids (TDS) during the pre-monsoon (PRM) and post-monsoon (POM) being 4435 mg/L and 4938 mg/L, respectively. Statistical results revealed that anion concentrations follow the order as Cl− > SO42− > HCO3− > NO3− while cation concentrations were Na+ > Ca2+ > Mg2+ > K+. The dominant hydrochemical types of Mewat groundwater were identified to be Ca2+.Mg2+- SO42−.Cl− and SO42−.Cl−- Na+. Silicate weathering, evaporation, and cation exchange were the three factors that control the composition of groundwater of Mewat. The chloro-Alkali indices indicate the dominance of direct base cation exchange reaction in the study area. Moreover, the results of the water quality evaluation showed that the values of WQI ranged from 72 to 3683 and 51 to 2451 during PRM and POM, respectively. WQI classes, namely Very poor and Poor water for drinking, are cumulatively represented by 64% and 58% of the total samples over the PRM and POM. And groundwater of Mewat was found mostly not suitable for drinking purposes. This is the first work in the Mewat district to assess the groundwater quality using WQI and their controlling hydrogeochemical process. This study provides insight into fundamental processes and aquifer controlling factors that are significant for the sustainable management of Mewat groundwater resources.

Delineation of groundwater potential zones at micro-spatial units of Nagaon district in Assam, India, using GIS-based MCDA and AHP techniques.

Groundwater is one of the most precious naturalresources in the densely populated regions of the world. The ever increasing population in the developing countries like India and the concurrent growth of industrial and urban centres along with modern agricultural systems have caused tremendous pressure on groundwater. In the present day context of groundwater depletion and degradation, it is necessary to identify and map the groundwater potential zones (GWPZs) of an area to manage and utilize them sustainably. The present study is, therefore, an attempt to employ the GIS-based multi-criteria decision analysis (MCDA) and analytical hierarchy process (AHP) techniques to derive the GWPZs in Nagaon district of the middle Brahmaputra valley agro-climatic region of Assam, India. Here, ten multi-influencing groundwater potential factors, including geology, lineament density, geomorphology, slope, soil texture, LULC, rainfall, drainage density, NDWI, and TWI are considered for the delineation ofGWPZs. These criteria are assigned weightages using AHP wherein geology has been given the highest weight, followed by lineament density and the others. Based on these techniques, the GWPZs of the district are classified into four zones, namely, low, moderate, high, and very high which include 20, 301, 218, and 392 villages, respectively. The results are validated with the groundwater levels of 28 tube wells and 5 ring wells distributed throughout the district, and as such, an area under the curve value of 86.9% is found. The results, thus, validated imply that the methodology adopted in deriving the GWPZs is highly reliable, which can help in sustainable utilization, development, and management of groundwater resources in the district. Besides, the identification and mapping of village-wise GWPZs are very essential for the planning of water resource management and water risks mitigation which ultimately help insustainable rural development.