Sustainable Use Of Groundwater Resources Research Articles

Groundwater investigation in the Dumoga area, north Sulawesi province, Indonesia

Dumoga is one of the areas in North Sulawesi Province, Indonesia, designated as an agriculture and food crop area. Groundwater is one of the sources of raw water and irrigation in this area. Therefore, it needs detailed information about the quantity and quality to support groundwater exploitation and management for sustainable use of groundwater resources. This study investigates the groundwater resource potential and quality, which has not been previously studied. The research methods used geological observation, springs mapping, geoelectrical survey, measurement of groundwater level, and physicochemical, including temperature, pH, total dissolved solids (TDS), and electrical conductivity (EC). The result shows that the Dumoga area has a high potential for groundwater resources, with sand and clayey sand as the main aquifers. Groundwater flows from around the research area to Dumoga River in the middle. Even though it has a high potential for groundwater resources, not all groundwater is recommended for irrigation water because of the quality, especially from the southwestern and eastern Dumoga areas.

GROUNDWATER DEPLETION IN AGRICULTURAL REGIONS: CAUSES, CONSEQUENCES, AND SUSTAINABLE MANAGEMENT: A CASE STUDY OF BASALTIC TERRAIN OF SOLAPUR DISTRICT

This research paper investigates the intricate dynamics of groundwater depletion in the agricultural region of Solapur, characterized by a basaltic terrain. The study unveils the multifaceted causes, consequences, and sustainable management strategies tailored to the unique geological and socio-economic conditions of Solapur. Over-extraction for irrigation, geological factors related to the low permeability of basaltic rocks, and specific agricultural practices have collectively contributed to a discernible decline in water table levels. The agricultural impacts are profound, with reduced crop yields and economic strains on farmers. Socioeconomic consequences extend to local communities, necessitating a holistic approach to address the challenges. The research proposes sustainable management strategies, including water conservation practices, localized policy interventions, community engagement, and technological innovations, designed to mitigate the adverse effects of groundwater depletion. These strategies, tailored to Solapurs conditions, showcase a pathway towards long-term resilience and sustainability. The case study of Solapur holds broader significance, serving as a microcosm for understanding and addressing groundwater depletion in agricultural regions globally. The complex interplay between geological, climatic, and anthropogenic factors underscores the importance of context-specific solutions and collaborative efforts to ensure the sustainable use of groundwater resources. The findings contribute valuable insights for policymakers, researchers, and communities striving to achieve water security and resilience in agricultural regions worldwide. KEYWORDS: Agricultural Regions, Basaltic Terrain, Groundwater Depletion, Solapur Case Study, Sustainable Management.

Seawater intrusion assessment in the Bir Guendouz-Boulanoire coastal transboundary aquifers of Morocco and Mauritania

The Bir Guendouz region, situated in Southern Morocco, is affected by saltwater intrusion. The transboundary aquifer is shared by Morocco and Mauritania, and it serves as the primary source of freshwater in this arid region. To differentiate between freshwater and saltwater areas, 750 non-invasive vertical electrical soundings (VES) were utilized along 42 perpendiculars to the coast. Dar-Zarrouk parameters—transverse resistance (Tr), longitudinal conductance (S), and longitudinal resistivity (ρl)— were determined using VES. These techniques remove uncertainties in resistivity interpretation that may arise due to the overlap between freshwater and saline aquifers during the process of suppression and equivalence. The results indicate a significant marine intrusion in the Bir Guendouz-Boulanoire aquifer, with varying degrees of salinization observed in different zones. Freshwater zones are identified by a transverse resistance of over 4450 Ω m2, a longitudinal conductance below 41.7 mho, and a longitudinal resistivity greater than 8.7 Ω m. These characteristics can be used to prevent saltwater intrusion and ensure the sustainable use of groundwater resources. Furthermore, they will aid in improving resource management between the two nations. The study's consequences also involve safeguarding the ecosystem and ensuring the longevity of these transboundary water resources. Therefore, for researchers, professionals, and decision-makers involved in sustainable management of transboundary groundwater, this study serves as a crucial reference.

Vertical distribution of groundwater age in and around the freshwater–saltwater transition zone determined using noble gases and carbon isotopes

The distribution of groundwater ages in coastal aquifers are complicated because of the heterogeneity of the hydrogeology and the mixing of terrestrial and marine water sources. Therefore, multiple studies verifying the groundwater age distribution via borehole surveys are required to better understand groundwater flow in coastal aquifers. This study examined groundwater age distributions in coastal aquifers adjacent to a high-elevation volcano (Mt. Fuji, Japan) by analyzing geochemical and isotopic tracers retrieved from drilling 350- and 160-m-deep boreholes. Brackish groundwater samples collected from the boreholes had high helium isotope ratios, indicating a large contribution of mantle-derived helium. Groundwater ages determined from carbon and helium isotopes indicate that terrestrial groundwater recharged at high elevations flows from the volcano to the coast, mixing with seawater in a transition zone. The groundwater age at the freshwater–saltwater transition zone and the upper part of the saltwater zone is older than that of the underlying saline water. The distributions of the groundwater age in the study area confirm that the conventional groundwater flow system in coastal aquifers is applicable even in deep aquifers. The complex patterns of groundwater age and mixing derived from geochemical and isotopic tracers can guide sustainable use of groundwater resources and the subsurface.

A multi-step approach to evaluate the sustainable use of groundwater resources for human consumption and agriculture

The rapid decline in both quality and availability of freshwater resources on our planet necessitates their thorough assessment to ensure sustainable usage. The growing demand for water in industrial, agricultural, and domestic sectors poses significant challenges to managing both surface and groundwater resources. This study tests and proposes a hybrid evaluation approach to determine Groundwater Quality Indices (GQIs) for irrigation (IRRI), seawater intrusion (SWI), and potability (POT), finalized to the spatial distribution of groundwater suitability involving water quality indicator along with hydrogeological and socio-economic factors. Mean Decrease Accuracy (MDA) and Information Gain Ratio (IGR) were used to state the importance of chosen factors such as level of groundwater above the sea, thickness of the aquifer, land cover, distance from coastline, silt soil content, recharge, distance from river and lagoons, depth to water table from ground, distance from agricultural wells, hydraulic conductivity, and lithology for each quality index, separately. The results of both methods showed that recharge is the most important parameter for GQIIRRI and GQIPOT, while the distance from the coastline and the rivers, are the most important for GQISWI. The spatial modelling of GQIIRRI and GQIPOT in the study area has been achieved applying three machine learning (ML) algorithms: the Boosted Regression Tree (BRT), the Random Forest (RF), and the Support Vector Machine (SVM). Validation results showed that RF has the highest prediction for GQIIRRI, while the SVM model has the highest prediction for the GQIPOT index. It is worth to mention that the future utilization and testing of new algorithms could produce even better results. Finally, GQIIRRI and GQIPOT were combined and compared using two combine and overlay methods to prepare a hybrid map of multi-GQIs. The results showed that 69% of the study area is suitable for irrigation and potable use, due to both geogenic and anthropogenic activities which contribute to make some water resources unsuitable for either use. Specifically, the northern, western, and eastern portions of the study area are in the “very high and high quality” classes while the southern portion shows “very low and low quality” classes. In conclusion, the developed map and approach can serve as a practical guide for enhancing groundwater management, identifying suitable areas for various uses and pinpointing regions requiring improved management practices.

The impact of water legislation on groundwater sustainability in an arid region: Spatial statistical approach

Sustainable use of groundwater resources and preservation of groundwater quality are critical issues for society as these resources directly impact the health of the environmental system and the population that rely on them for consumption. Despite this, and considering the importance of legal frameworks for establishing and enforcing sustainable practices, there is a lack of research looking at the effectiveness of environmental legislation on groundwater resources which ultimately inhibits opportunities for improvement. Considering this, this study aims to investigate the impact of water legislation on groundwater usage in Jordan, a small country located in a typically arid region, using hotspot analysis (HSA) and time series trend analysis (TA). In addition, the study assesses legislation's effectiveness on groundwater quality through data collected on static water level, water extractions, total dissolved solids (TDS), chloride (Cl−), and nitrate (NO3−).The study results show that the groundwater levels declined (average of 1 m/yr) in most of the monitored wells in the observed time irrespective of the legislation implemented to monitor and reduce extraction. In fact, the HSA results showed a significant increase in the volume of water extracted after legislation was introduced. In addition, water quality also deteriorated particularly in areas of intensive agricultural activity where there are high levels of water usage and chemical run-off. In particular, TDS and Cl-levels increased during the assessed period by more than 40% over the Jordanian standards for drinking water.As such, the study concludes that existing legislation has been ineffective at preserving groundwater quantity and quality. It is therefore recommended that legislation be reformed to ensure that quality standards are upheld and extraction of groundwater resources is permitted at sustainable rates without exceeding the basin yield. This could be achieved by implementing an integrated institutional framework that better facilitates coordination between relevant ministries; introducing an advanced monitoring system; substituting existing crops for low-water use crops; introducing higher tariffs; and enforcing a stricter penalty system.

The risk assessment of arsenic contamination in the urbanized coastal aquifer of Rayong groundwater basin, Thailand using the machine learning approach

The rapid expansion of urbanization has resulted in an insufficient of groundwater resource. In order to use groundwater more efficiently, a risk assessment of groundwater pollution should be proposed. The present study used machine learning with three algorithms consisting of Random Forest (RF), Support Vector Machine (SVM), and Artificial Neural Network (ANN) to locate risk areas of arsenic contamination in Rayong coastal aquifers, Thailand and selected the suitable model based on model performance and uncertainty for risk assessment. The parameters of 653 groundwater wells (Deep=236, Shallow=417) were selected based on the correlation of each hydrochemical parameters with arsenic concentration in deep and shallow aquifer environments. The models were validated with arsenic concentration collected from 27 well data in the field. The model’s performance indicated that the RF algorithm has the highest performance as compared to those of SVM and ANN in both deep and shallow aquifers (Deep: AUC=0.72, Recall=0.61, F1 =0.69; Shallow: AUC=0.81, Recall=0.79, F1 =0.68). In addition, the uncertainty from the quantile regression of each model confirmed that the RF algorithm has the lowest uncertainty (Deep: PICP=0.20; Shallow: PICP=0.34). The result of the risk map obtained from the RF reveals that the deep aquifer, in the northern part of the Rayong basin has a higher risk for people to expose to As. In contrast, the shallow aquifer revealed that the southern part of the basin has a higher risk, which is also supported by the location of the landfill and industrial estates in the area. Therefore, health surveillance is important in monitoring the toxic effects on the residents who use groundwater from these contaminated wells. The outcome of this study can help policymakers in regions to manage the quality of groundwater resources and enhance the sustainable use of groundwater resources. The novelty process of this research can be used to further study other groundwater aquifers contaminated and increase the effectiveness of groundwater quality management.

Behaviour of Groundwater Table with Rainfall in North-West Region of Bangladesh

Groundwater is the major source of water to meet up the vast domestic and agricultural demand in Bangladesh. Additionally, reduction in reliable surface water resources resulting the increased reliance on groundwater day by day. Therefore, monitoring the groundwater fluctuation over time is crucial to ensure the sustainable use of groundwater resources in future. The present study analyzed historical groundwater data to know the behaviour of groundwater at four locations of two districts Pabna and Rangpur in the North-Eastern part of the country. Historical groundwater level data and monthly rainfall data from 1989 to 2017 were collected from Bangladesh Water Development Board and Bangladesh Meteorological Department, respectively. The annual maximum groundwater table depth (MaxGWT) and minimum groundwater table depth (MinGWT) and its trend was analyzed, and positive and negative recharge years were identified from these values. We found the maximum declining rate at 6.6 cm annually and the maximum 205 cm total depletion in the study area. The number of years of negative recharge is more than that of positive recharge for 32 years. As a result, a declining trend in groundwater table was found at three locations of the study area. The maximum groundwater table remains below suction limit at Ishwardi, causes no shallow tubewell (STW) works during that period. A declining trend in annual rainfall is observed in Pabna district. A linear relationship between rainfall and recharge was found at two locations of the study area. Bangladesh Rice J. 25 (2) : 85-95, 2021

Hydrochemical controls on arsenic contamination and its health risks in the Comarca Lagunera region (Mexico): Implications of the scientific evidence for public health policy.

Nearly half of the world's urban population depends on aquifers for drinking water. These are increasingly vulnerable to pollution and overexploitation. Besides anthropogenic sources, pollutants such as arsenic (As) are also geogenic and their concentrations have, in some cases, been increased by groundwater pumping. Almost 40 % of Mexico's population relies on groundwater for drinking water purposes; much the aquifers in semi-arid and arid central and northern Mexico is contaminated by As. These are agricultural regions where irrigation water is primarily provided from intenstive pumping of the aquifers leading to long-standing declines in the water table. The focus of this study is the main aquifer within the Comarca Lagunera region in Northern Mexico. Although the scientific evidence demonstrates that health effects are associated with long-term exposure to elevated As concentrations, this knowledge has not yielded effective groundwater development and public health policy. A multidisciplinary approach - including the evaluation of geochemistry, human health risk and development and public health policy - was used to provide a current account of these links. The dissolved As concentrations measured exceeded the corresponding World Health Organization guideline for drinking water in 90 % of the sampled wells; for the population drinking this water, the estimated probability of presenting non-carcinogenic health effects was >90 %, and the lifetime risk of developing cancer ranged from 0.5 to 61 cases in 10,000 children and 0.2 to 33 cases in 10,000 adults. The results suggest that insufficient policy responses are due to a complex and dysfunctional groundwater governance framework that compromises the economic, social and environmental sustainability of this region. These findings may valuable to other regions with similar settings that need to design and enact better informed, science-based policies that recognize the value of a more sustainable use of groundwater resources and a healthier population.

Post Monsoon Season Spatial Distribution of Groundwater Depth over the Low-Lands of Sunsari District of Eastern Nepal

The knowledge and an accurate representation of the spatial distribution of groundwater depth of an area are very important to realize sustainable use of groundwater resource, protection of ecosystem and for the development of adaptation policies in the changing climate. The present study has, thus, developed a groundwater depth distribution map of southern low-lands of the Sunsari District at the horizontal grid resolution of 3 km × 3 km. The groundwater depths were surveyed at predefined 82 numbers of geo-referenced grid points scattered over the region during the post monsoon season of the year 2019. Referencing the sampled depths, spatial distribution of the groundwater depth over the area has been predicted using the Ordinary Kriging Method. Three widely used Semivariogram modules such as Spherical, Exponential, and Gaussian were implemented. The Gaussian model of Semivariogram outperformed the other methods with R2 of 0.336, RMSE of 2.591, and MAE of 1.946. The predicted spatial distribution of groundwater depth reasonably well correlated with the observed distribution. The spatial distribution of groundwater level suggests that 12.36% the total area, particularly, over the western, southwestern and northern parts hold groundwater at much shallower depth (< 5 m). Over 51.59 % of the total area in the southeastern and northeastern parts, the groundwater level remained below 8 m from the ground and the rest of the total area holds the groundwater deeper than 8 m.

Sustainable management of groundwater extraction: An Australian perspective on current challenges

Study regionAustralia Study focusOur incomplete knowledge of groundwater systems and processes imposes barriers in attempting to manage groundwater sustainably. Challenges also arise through complex institutional arrangements and decision-making processes, and the difficulty in involving stakeholders. In some areas, these difficulties have led to water table decline and impacts on groundwater users and groundwater-dependent ecosystems. However, there is potential to improve the sustainable use of groundwater resources through improvements in management practices. We discuss some of the challenges, and present survey results of research, government, and industry professionals across the groundwater sector in Australia. New hydrological insights for the regionThe highest-ranked challenge identified in the survey was the difficulty in determining regional-scale volumetric water extraction limits. This is surprising given the criticism in the international literature of volumetric based approaches for groundwater management, and the decreased reliance on this approach in Australia and elsewhere in recent years. Other major challenges are the difficulty in determining and implementing maximum drawdown criteria for groundwater levels, determining water needs of ecosystems, and managing groundwater impacts on surface water. Notwithstanding these gaps in technical understanding and tools and a lack of resources for groundwater studies, improvements in stakeholder communication should enable more effective decision-making and improve compliance with regulations designed to protect groundwater and dependent ecosystems.

Water stress and the expenditure in zoning violated areas of Chennai: An empirical investigation

India as the largest user of groundwater in the world faces the risk of resources depletion and degradation. The study focuses on groundwater degradation and drinking water expenditure in 45 locations of 15 Zoning Violated Areas (ZVAs) in Chennai. We collected 45 groundwater samples in each pre- and post-monsoon seasons for testing heavy metals concentration levels and compared them with the World Health Organization (WHO)/the Bureau of Indian Standards (BIS) drinking water standards. We surveyed 797 households in the 14 ZVAs and statistically analysed drinking water expenditure. Scientific analysis reveals that Cadmium and Nickel are 15 and 7 times higher than the WHO/BIS standards in Nagalkeni of Pammal area. The analysis also shows that higher levels of concentrations of Lead, Nickel, Chromium and Cadmium in the groundwater in 25, 13, 3 and 1 locations respectively. Survey analysis indicates that 3,21,102 households have incurred an aggregate expenditure of $52.72 million per year on drinking water. The analysis shows that each of the economically weaker, lower-middle and upper middle-income groups spend, on average, 11.64, 4.72 and 2.55 per cent of their daily income, respectively on drinking water. The study also informs that Pammal is the most vulnerable area in groundwater contamination and households in Ambattur area has incurred highest expenditure on drinking water. The regression analysis of the data reveals that variables, such as metro water, income and family size are statistically significant in explaining the water expenditure. The Computable General Equilibrium model for Chennai estimates shows that the increase in water resources and economic growth under the assumption that all the households will, and economically weaker sections will not, contribute to investments for drinking water resources. The study proposes a household-right-to-know legislation, adequate metro water supply and an incentive-structured compatible land-use regulation to achieve sustainable use of groundwater resources.

A GIS-Based Hydrogeological Approach to the Assessment of the Groundwater Circulation in the Ischia Volcanic Island (Italy)

Assessing the variations in space and time of groundwater circulation in volcanic islands is of paramount importance to the description of the hydro-geo-thermal system and implementation of hydrogeological, geochemical, and volcanic monitoring systems. In fact, the reliable reconstruction of the groundwater potentiometric surface in such composite volcanic aquifer systems can enable the identification of the most advantageous strategies for both the sustainable use of groundwater resources and the management of volcanic risk. Geographical Information System (GIS) platforms can support the integration and analysis of many spatial and temporal variables derived from monitoring of active volcanoes and the elaboration of spatially continuous data. However, open issues still affect the reliability and general applicability of common spatial interpolation methods in the case of groundwater potentiometric surfaces. This is related to the assessment of the main stratigraphic and volcano-tectonic features affecting the hydraulic head changes. With regard to the dynamically very active Ischia Island (Italy), this study illustrates a GIS-based hydrogeological approach to identify the most accurate interpolation method for mapping the potentiometric surface in complex hydrogeological terrains. The proposed approach has been applied to the existing dataset (1977–2003) stored by Istituto Nazionale di Geofisica e Vulcanologia. Based on a careful geological and hydrogeological survey, a total of 267 wells, from 5 to 250 m in depth, were processed. The data pre-processing involved four meteorological time-series data (1922–1997) and six long records of piezometric water levels (1930–1994). As a result, knowledge of the delineation of rather homogeneous stratigraphic and volcano-tectonic structures at the basin-scale has improved. Thus, new, more reliable potentiometric surfaces of the four main geothermal areas closest to the coast were produced during both dry and wet seasons. The reliability of the processed potentiometric surface was then validated by comparing the spatially continuous data with complementary field data. These findings point toward an optimal interpolation approach for representing the seasonal and areal distribution of main hydrogeological parameters in complex aquifer systems. Finally, insights into variations of hydrological behavior at an active volcanic area will foster an understanding of possible involvement of fresh and thermal waters in triggering phreatic explosions.

INV-FLOW: New Possibilities to Evaluate the Technical Condition and Function of Extraction Wells

The declining supply of available groundwater resources is increasing the importance of extraction wells. To maximize the yield of extraction wells, the operators do not always respect the sustainable use of groundwater resources. These efforts can affect water quality and impact the service life of an extraction well, mainly through the clogging process. As part of the INV-FLOW project, an apparatus for evaluating the functionality of an extraction well by measuring the vertical water flow through its screen and filter was designed and tested. The apparatus consists of two electromagnetic induction flowmeters, two pneumatic seals, and a pump with the possibility of regulation. After an initial laboratory verification of the fundamental concept, the apparatus was successfully tested in real conditions. Two extraction wells, HJ-3 and HJ-4, intended for water supply to an agricultural production plant, were measured at a pilot site in the Czech Republic using the INV-FLOW apparatus. Although the HJ-3 extraction well is at the end of its service life, the HJ-4 extraction well is a newly installed well. In the new extraction well, HJ-4, a high proportion of water flowing through the gravel pack relative to the total pumping flow (93–97%) was measured using the INV-FLOW apparatus at different pumping rates. In the case of the HJ-3 extraction well, screen and filter clogging contributed significantly to the limited water flow through the gravel pack. In the most affected parts of the extraction well (15–20 m b.g.l.), the proportion of water flowing through the gravel pack relative to the total pumping flow ranged from 10 to 20%. The pilot tests confirmed the functionality of the apparatus and the possibility of using it to evaluate the degree of clogging and incrustation of an extraction well. The pilot tests thus demonstrated the usability of the INV-FLOW apparatus. The extraction well operator can assess the level of clogging or incrustation of the extraction well and decide on the need for the rehabilitation of an extraction well, or the termination of its operation.

Hydrogeochemistry of the groundwater system of the transboundary basement and volcanic aquifers of the Bulal catchment, Southern Ethiopia

The evaluation of groundwater geochemistry of transboundary aquifers has an important role in the management and sustainable use of groundwater resources in arid and semi-arid regions. This study presents the results of an integrated hydrogeochemical study of the Bulal transboundary aquifers located in the Borena zone, along the Ethiopia-Kenya border. The main aquifers are basic volcanic rocks, subordinate felsic pyroclastic deposits, and metamorphic basement rocks. These aquifers are overlain by alluvio-lacustrine sediments, eluvial soil and regolith. The groundwaters are dominated by Na+ and HCO3− and mixed water types. Silicate weathering and evaporation are the dominant hydrogeochemical processes controlling the chemistry of the groundwaters in most parts of the catchment. However, dissolution of evaporitic minerals might have also played a significant role in adding major ions into the groundwater system. Groundwater in the volcanic aquifers are Na–HCO3, Ca–Mg–HCO3, Na–Ca–HCO3 and Na–Cl–SO4 water types while Ca–Mg–HCO3, Na–Ca–Cl–SO4 and Ca–Mg–SO4 water types are dominant in the metamorphic basement aquifers. The groundwater in the catchment mainly evolved from Na–HCO3 in the west, Ca–Mg–HCO3 in the north, and Na–Ca–Cl–SO4 in the central east and southeast to Na–Ca–HCO3 type in the southern low-lying areas along the groundwater flow direction. The study has significant implications for the management of groundwater quality in the region.

A new groundwater depth prediction model based on EMD-LSTM

Abstract Groundwater resources play an important role in life, but the lack of effective management of groundwater resources has led to a regional decline in groundwater levels. How to curb the over-exploitation of groundwater and realize the sustainable use of groundwater resources has become an important issue for ecological environmental protection. Therefore, accurate prediction of groundwater depth is an important foundation for the rational use of groundwater resources. Based on the significant advantages of empirical model decomposition (EMD) in dealing with non-smooth and nonlinear data and the long-term memory function of long and short-term memory (LSTM) network, a coupled EMD-LSTM-based groundwater prediction model is constructed and apply to groundwater depth prediction of three professional observation wells. The results show that the maximum relative error of the prediction results of the EMD-LSTM model for the three professional observation wells is 5.00% and the minimum is 0.07%. The prediction passing rate is 100% and the prediction accuracy of the coupled model for groundwater depth is higher than that of the single LSTM model and back-propagation (BP) model. In conclusion, the model has high prediction accuracy and provides an effective method for the prediction of groundwater depth. HIGHLIGHTS Empirical mode decomposition (EMD) is a relatively novel data preprocessing method that can effectively reduce the non-smoothness of time series. LSTM is considered to be superior in terms of learning rate and generalization ability. The EMD-LSTM coupled model has better nonlinear and complex process learning ability in groundwater forecasting.

Identifying the impact of crop distribution on groundwater resources carrying capacity in groundwater-depended agricultural regions

Groundwater resources carrying capacity (GRCC) is defined as the capacity of groundwater resources for supporting social-economic development, which has been incredibly reduced in groundwater-depended agricultural regions due to unreasonable use of groundwater resources. Identifying the key factors influencing GRCC and providing the optimal strategy is critical for sustainable use of groundwater resources. The present study used the improved GRCC index, regression functions, and random forest to identify the key factors influencing the GRCC in a groundwater over-exploited area [Zhangjiakou, Hebei province, China (ZJK)]. And the particle swarm optimization and optimal water allocation model were used to select the best crop distribution scenarios for improving the GRCC. The results showed that IncMSE index (random forest) for each influencing factors ranging from − 3.4–8.9, indicating that crop distribution is the most important factor affecting the GRCC. Therefore, changing the crop distribution is the key factor to improve the GRCC in ZJK. The results of optimizing crop distribution scenarios showed the total water use for optimized crop distribution O26 (potato and cabbage planting area were 36,885 and 362,936 ha) was 713,701,500 m3, which was reduced by 14% compared to base scenarios in 2016. Furthermore, the GRCC index (D) has decreased by 53%～83%, which means the groundwater resources would be sustainable by using this crop distribution with irrigation quotas are 900 and 1875 m3/ha respectively. The results can provide decision-making references for sustainable use of groundwater resources in groundwater over-exploitation regions.

Exploring long-term impacts of different crop rotation systems on sustainable use of groundwater resources using DSSAT model

Groundwater depletion has been a global concern due to unreasonable agricultural water managements. Identifying long-term impacts of crop rotation systems on hydrological parameters and crop yields can help to alleviate groundwater depletion. The Decision Support System for Agro-technology Transfer model was applied to simulate impacts of nine crop rotation systems (H1: continuous spring maize; H2: continuous potato; H3: continuous spring wheat; H4:potato-maize rotation; H5:maize-wheat rotation; H6: wheat-potato rotation; H7: two year fallow-maize rotation; H8: two year fallow-potato rotation; H9: two year fallow-wheat rotation) on crop evapotranspiration, percolation, yields, water use efficiency, net water use and groundwater table depth changes in Zhangjiakou, China from 1985 to 2018. The results showed DSSAT model performed well in simulating crop ET, yields (R2>0.9, RMSE<500 kg ha−1) and soil water content (R2>0.9 and RMSE<10.1 mm). The long-term two year fallow with one single crop rotation systems (H7 to H9) had lower total accumulative groundwater table depth changes (2.8–14.4 m) than others (12.7–52.3 m) from 1985 to 2018. Also, cropping rotation systems H7 to H9 obtained the lower annual average net water use (14–70 mm) compared to other cropping rotation systems (62–253 mm). The significant difference of net water use, crop yields, water use efficiency and accumulative groundwater table depth changes of nine different cropping systems indicated H4 and H8 is suitable in the study region. Our results is useful for selecting suitable cropping systems based on the water use for local farmers.

Opportunities and challenges for implementing managed aquifer recharge models in drought-prone Barind tract, Bangladesh

This study focuses on the Barind tract, a drought prone area situated in the north-west region of Bangladesh where inadequate rainfall and limited surface water have created high dependence on groundwater for irrigation and other purposes, leading to significant declines in groundwater level. Managed aquifer recharge (MAR) offers a potential solution to restore groundwater levels. This study sets out to identify the opportunities and challenges for implementing MAR in the Barind tract. To accomplish this aim, different data sets including bore log lithology, rainfall, groundwater levels, information about re-excavated ponds, dighis, kharies, beels, check dams, rubber dams, dug wells and other necessary information were collected from the Barind Multipurpose Development Authority (BMDA) and other sources and analyzed. Major opportunities for MAR are identified for about 2000 km of re-excavated kharies (canals) containing about 750 check dams, more than 3000 re-excavated ponds, a number of beels (comparatively large marshes) and other water bodies which are used to conserve runoff storm water for supplementary irrigation. The conserved water can be used for groundwater recharge and subsequently abstracted for irrigation. Furthermore, roof-top rain water from buildings can also be used for groundwater recharge purposes. In contrast, the major challenges include the high turbidity of storm water runoff leading to clogging of MAR structures, inadequacy of conventional direct surface methods of recharge due to the presence of a 15 m or more thick upper clay layer with limited percolation capacity, and lack of practical knowledge on MAR. Therefore, overcoming the challenges for MAR application is a prerequisite to maximize the opportunities from MAR that can support the sustainable use of groundwater resources.

Linking local natural background levels in groundwater to their generating hydrogeochemical processes in Quaternary alluvial aquifers

Calculating natural background levels (NBLs) in groundwater is vital for supporting a sustainable use of groundwater resources. Although NBLs are often assessed through a unique concentration value per groundwater body, where hydrogeochemical features are highly variable, spatial heterogeneity needs to be accounted for, leading to the calculation of so-called “local” NBLs. Despite much research devoted to the identification of the best performing techniques for local NBLs spatialization, a deep understanding of the link between local NBL values and their generating hydrogeochemical processes is often lacking and so is addressed here for the redox-sensitive species As, NH4, Fe and Mn in the groundwater bodies of Lombardy region, N Italy.Local NBLs were calculated by a tired approach involving the hybridization of preselection and probability plot methods. Since the spatial variability of the target species depends mainly on redox conditions, a redox zonation was performed using multivariate statistical analysis. A conceptual model was developed and improved combing factor and cluster analysis. Results showed that NBLs for arsenic were up to 291 μg/L, reached in groundwaters under methanogenesis, a condition related to the prolonged degradation of peat buried in aquifer sediments. Ammonium NBLs up to 6.62 mg/L were generated by the upwelling of fluids from deep sediments hosting petroleum systems; ammonium NBLs up to 4.48 mg/L were generated as the accumulation of by-products of peat degradation. Iron and manganese NBLs up to, respectively, 6.0 and 1.51 mg/L were generated by the oxidation of younger and less stable Mn and Fe oxides within river valleys, mostly the Po River valley.The evaluation of local NBLs, and their association to generating natural hydrogeochemical processes/conditions, achieves a step forward from the commonly used approach of a single NBL per groundwater body, improving decision-support tools for sustainable groundwater management and protection.