Groundwater Overexploitation Research Articles

Global Impact of Sea Level Rise on Coastal Fresh Groundwater Resources

AbstractGroundwater is the main freshwater source in many densely populated and industrialized coastal areas around the world. Growing future freshwater demand is likely to increase the water stress in these coastal areas, possibly leading to groundwater overexploitation and salinization. This situation will likely be aggravated by climate change and the associated projected sea level rise. Here, we assess the impact of sea level rise exclusively on coastal fresh groundwater resources worldwide (limited to areas with unconsolidated sedimentary systems) by estimating future decline in inland fresh groundwater volumes under three sea level rise scenarios following Representative Concentration Pathway (RCP) 2.6, 4.5, and 8.5. For that, 2D groundwater models in 1,200 coastal regions estimate the past, present and future groundwater salinity. Our results show that roughly 60 (range 16–96) million people living within 10 km from current coastline could lose more than 5% of their fresh groundwater resources by 2100 according to RCP 8.5 scenario compared to only 8 (range 0–50) million people based on RCP 2.6 scenario. We conclude that sea level rise will have severe consequences for many coastal populations heavily dependent on fresh groundwater.

Spatial and Temporal Patterns of Land Subsidence and Sinkhole Occurrence in the Konya Endorheic Basin, Turkey

The endorheic Konya Basin is a vast aggradational plain in Central Anatolia, Türkiye. It occupies a significant portion of Konya Province, covering approximately 50,000 km2. The basin is subjected to intense groundwater withdrawal and extensive agricultural activities with excessive irrigation. These activities have led to human-induced hazards, such as sinkholes and regional land subsidence. Although sinkhole occurrence mainly occurs in the Karapınar area, land subsidence is primarily observed in the central sector of Konya city, with 2 million inhabitants, as well as in various parts of the basin. This study focuses on determining the extent and rate of land subsidence throughout the basin, understanding sinkhole formation, and unraveling their relationship with anthropogenic activities. For this purpose, Interferometric Synthetic Aperture Radar (InSAR) analysis of Sentinel-1 data from 2014 to 2022 was conducted to identify and assess land subsidence. We also used the land cover data and groundwater-level information to better understand the spatial and temporal patterns of land subsidence and sinkhole occurrence. Additionally, the land cover data were used to resolve spatial–temporal variations in the cultivated area and urbanization, which are the main factors governing groundwater exploitation in the region. Our study identified widespread subsidence zones with rates as high as 90 mm/y. Groundwater overexploitation to sustain extensive agricultural operations is the main cause of the high rate of land subsidence. Additionally, it was discovered that the number of sinkholes has substantially increased due to anthropogenic influences, currently amounting to as many as 660.

Rapid spatio-temporal pumping volume estimation from electricity consumption big data

Land subsidence due to groundwater over-exploitation is a serious problem worldwide. Acquiring total pumping volumes to assess the stresses imposed that lead to subsidence is often difficult to quantify because groundwater extraction is often an unregulated water source. Consequently, pumping volumes represent a critical step for water resource managers to develop a strategic plan for mitigating land subsidence. In this investigation, we develop a time-dependent spatial regression (TSR) model to estimate monthly pumping volume over a ten-year period based on electricity consumption data. The estimated pumped volume is simplified as the spatial function of the electricity consumption and the electric power used by the water pump. Results show that the TSR approach can reduce the errors by 38% over linear regression models. The TSR model is applied to the Choshui alluvial fan in west-central Taiwan, where hundreds of thousands of unregulated pumping wells exist. The results show that groundwater peak extraction across the region occurs from January to May. Monthly pumping volume, and rainfall information are available to provide a better understanding of seasonal patterns and long-term changes of subsidence. Thus, the temporal regional subsidence patterns are found to respond to variations in pumping volume and rainfall.

Impact of Groundwater Depletion on Irrigation Cost of Paddy and Maize Cropping System in the Anantapur District of Andhra Pradesh, India

The study was conducted to estimate the cost of groundwater irrigation and the impact of groundwater over-exploitation on the irrigation cost of paddy and maize in the Anantapur district of Andhra Pradesh. Based on the stage of groundwater extraction, the Central Groundwater Board divided the study area into safe and exploited areas. Primary data was collected from both these safe and exploited areas. The study found that the annual irrigation cost of groundwater in over-exploited areas for both paddy (₹4033.38/acre) and maize (₹3570.26/acre) were observed to be higher as against paddy (₹2697.01/acre) and maize (₹ 2524.76/acre) in safe areas. The added cost of groundwater irrigation in over-exploited areas for paddy (₹988.08/acre) and maize (₹838.34/acre) were preponderantly greater than paddy (₹216.60/acre) and maize (₹187.82/acre) in safe areas. This revealed that groundwater over-exploitation had a more significant impact on over-exploited regions. Marginal and small farmers are the primary victims of groundwater over-exploitation in terms of cost and groundwater resources. Free/subsidized electricity for irrigation and water-intensive crops, paddy and maize, are one of the reasons for depleting groundwater in the study area. There is a solid requirement for controlling groundwater over-exploitation in the study area.

The role of nanoscale zero-valent iron (nZVI) in remediation of heavy metal contamination in groundwater overexploitation areas

This study investigates the remediation of groundwater contaminated with heavy metals in overexploited areas using a modified approach involving the use of corn plant parts to produce biochar. The biochar was modified using a hydrothermal method, employing nanoscale zero-valent iron (nZVI) material to create a composite material for adsorbing heavy metals from water bodies. Adsorption experiments were conducted on the presence of Cr, Cu, and Zn ions in the water. The experimental investigations focused on the dosage of adsorption materials, solution pH, and stability of the adsorption material to validate the enhanced capability of the nanoscale zero-valent iron modified biochar composite (Fe-CBC-MO) for removing and adsorbing heavy metal ions (Cu, Cr, and Zn) from water. The results indicate that the adsorption capacity follows the sequence: Cr > Zn > Cu. Increasing the adsorbent dosage provides more adsorption sites, thereby improving the removal efficiency of heavy metals from water bodies. Considering cost-effectiveness, an optimal dosage of 0.15 g was selected. Under alkaline conditions, Cu and Zn ions precipitated significantly, leading to sustained high removal rates of heavy metals. Correspondingly, the rate constants were also relatively high. In acidic environments, the rate constant for Cr decreased significantly due to corrosion passivation. The composite material Fe-CBC-MO exhibited remarkable removal efficiency for all three heavy metals (Cr, Cu, Zn), demonstrating a strong capability for remediating heavy metal pollution.

Monitoring and Analysis of Land Subsidence in Cangzhou Based on Small Baseline Subsets Interferometric Point Target Analysis Technology

Cangzhou is located in the northeast part of the North China Plain; here, groundwater is the main water source for production and living. Due to the serious regional land subsidence caused by long-term overexploitation of groundwater, the monitoring of land subsidence in this area is significant. In this paper, we used the Small Baseline Subsets Interferometric Point Target Analysis (SBAS-IPTA) technique to process the Envisat-ASAR, Radarsat-2, and Sentinel-1A data and obtained the land subsidence of Cangzhou from 2004 to 2020. Additionally, we obtained winter wheat distribution information in Cangzhou using the Pixel Information Expert Engine (PIE-Engine) remote sensing cloud platform. On this basis, we analyzed the relationship between ground water level, winter wheat planting area, and the response of land subsidence according to the land use type and groundwater level monitoring data near the winter wheat growing area. The results show that during 2004–2020, the average annual subsidence rate of many places in Cangzhou was higher than 30 mm/year, and the maximum subsidence rate was 115 mm/year in 2012. From 2004 to 2020, the area of the subsidence funnel showed a trend of first increasing and then decreasing. In 2020, the subsidence funnel area reached 6.9 × 103 km2. The winter wheat planting area in the urban area showed a trend of first decreasing, then increasing and then decreasing, and it accounted for a large proportion in the funnel area. At the same time, we studied the relationship between the land subsidence rate and the water level at different burial depths and the response of winter wheat planting area. The results showed that the change of confined water level had a stronger response with the other two variables.

Analysis and evaluation of groundwater pollution in Shouguang, China

AbstractGroundwater is an essential nonrenewable resource for agricultural activities. In this study, groundwater samples were collected from the Shouguang area, and the level of groundwater contamination was investigated by measuring the NO3−, SO42−, F−, Cl−, Ca2+, Mg2+, total dissolved solids (TDS) and chemical oxygen demand (COD). Exploratory data analysis was employed initially to study the hydrochemical characteristics and the sources of pollutants. Finally, the groundwater quality was measured using principal component analysis, entropy weight and complex correlation coefficient methods. As a common observation, the groundwater in the Shouguang area is slightly alkaline, so Ca2+, Mg2+ and NO3− acted as predominant pollutants. These contaminants originated from the excessive use of chemical fertilizers and large‐scale sewage irrigation. Second, perennial overexploitation of groundwater in Shouguang led to the generation of funnels and led to seawater intrusion. As a result, Cl− and TDS in the water samples collected from the north Shouguang area exceeded the regulatory guideline value, which indicates the risk of land salinization. However, the measured concentrations of SO42−, F− and COD were within the normal range. This confirms the minimal contribution of industries to groundwater pollution. East of the Ni River the groundwater is severely polluted, and the detected concentrations of pollutants are far beyond the standard limit and pose a potential risk to human health. Therefore, protection and treatment are urgently needed.

Modifying physical supply and use tables (PSUTs) in the system of environmental-economic accounting (SEEA) for off-farm irrigation water management

A reliable water accounting framework is crucial for understanding the contribution of water resources in meeting agricultural demands and selecting appropriate operating systems for off-farm water systems, including hydraulic conveyance and distribution structures. This ensures fair, adequate, and dependable irrigation water distribution, especially under water scarcity operational scenarios. This study presents a novel and effective method for modifying PSU tables in the SEEA water accounting framework that is specifically designed for small-scale agricultural water management study areas. The proposed approach entails a comprehensive analysis of the surface water distribution within the water holders using a hydraulic simulation model and a spatial analysis of the groundwater extraction for meeting on-farm water demands. This approach was implemented on Iran's Central Plateau and revealed notable variations in water rights and distribution effectiveness among stakeholders so that, surface water contributed 27–40% less than the legal water rights, leading to aquifer overexploitation. The evaluation indicated that changing crop patterns and upgrading to pressurized irrigation systems led to 4–7.5% overexploitation of groundwater and 3.5–6% water conservation on farm scales. Besides, the spatial assessment verified a considerable overlap of 59% between the farms with modern irrigation systems and those with cultivated area expansion, resulting in sustained overexploitation pressure on the aquifer. The present study has two significant practical implications. Firstly, it specifies the contribution of surface- and groundwater resources in fulfilling the water demands of individual water-holders. Secondly, it provides reliable information to decision-makers about the incentives for modernization, rehabilitation, and renovation projects in an irrigation district.

Attenuation of the contribution of groundwater to a wetland caused by groundwater overexploitation

AbstractThe continuous exploitation of groundwater has made wetland degradation an ecological and geological environmental problem that cannot be ignored and has had impacts on the ecological environment and human production and life. In this study, Modflow was used to simulate the wetland‐aquifer interaction during the multiyear pumping process, establish a quasi‐ideal model of wetlands based on the actual area of the Baiyangdian Basin, simulate the relationship of water quantity change between wetlands and piedmont plain aquifers during groundwater exploitation and its natural recovery process, and quantify the attenuation of the contribution of groundwater to wetlands caused by groundwater overexploitation. Two components of wetland water reduction are explored through the simulation and calculation of wetland‐aquifer interactions under different exploitation conditions. The results show that in the process of groundwater exploitation, the impact of groundwater overexploitation on wetland degradation is mainly divided into two parts: one is the reduced base flow from the piedmont plain to the wetland, and the other is the induced infiltration caused by the reverse recharge of groundwater from the wetland due to the pumping effect. Compared with the wetland water reduction during the pumping process, the process of water recovery during the natural recovery process is much slower, which indicates the residual effect of exploitation will continue for a long time. The findings provide a scientific reference for the management of water resources in wetland areas.

A numerical simulation study on the evolutionary characteristics of the damage process of karst soil cavity under positive pressure effect

Positive pressure effect is the result of rapid urban development in recent years, which leads to over-exploitation of karst groundwater, coupled with the emergence of extreme weather (such as heavy rainfall, the increase in the duration of heavy rainfall), leading to the sharp rise of karst water level, the gas in the karst cavity can not be discharged in time to form a high positive pressure in the soil cavity and promote the destruction of the soil layer, which then induces a series of phenomena, such as karst subsidence. As a new collapse mechanism, the positive pressure effect causes geological disasters that seriously affect the safety of people's lives and properties in karst regions. In order to study the damage characteristics and evolution characteristics of karst soil cavities under positive pressure effect, this study is based on the ASCII text provided by FLAC itself, and the orthotropic simulation computation compilation program, which realizes the finite element analysis in FLAC3D, and focuses on the inhomogeneous change of soil displacement, redistribution of stresses, and plastic damage of karst soil cavities in different evolution stages under the action of positive pressure, and summarizes the characteristics and laws of stress, strain and damage in plastic zone of karst soil cave at different stages of evolution. The results will play a positive role in further investigating the potential mechanical effects, development mechanism and critical warning conditions during the evolution of covered karst soil caves, and also have important scientific research value in deepening the theory of prevention and control of collapse disasters in covered karst soil caves.

Water Resources in Jordan: A Review of Current Challenges and Future Opportunities

Jordan is facing significant challenges related to water scarcity, including overexploitation of groundwater, increasing demand, and wasteful practices. Despite efforts to manage water resources, inadequate planning has resulted in ongoing water security concerns and deteriorating water quantity and quality. To address water stress, Jordan has implemented measures such as desalination, dam construction, and water conservation initiatives. However, water stress remains high, necessitating a comprehensive strategy that includes short-term demand-side interventions and long-term supply-side reforms. Financial and governance challenges hinder the implementation of these measures, requiring private investment and coordination among stakeholders. This paper provides a comprehensive review of Jordan’s water resources, analyzing current trends, challenges, and opportunities. The aim is to offer insight into the current situation and propose sustainable management approaches. The findings will be valuable for policymakers, researchers, and stakeholders working towards addressing Jordan’s complex water challenges and securing a sustainable water future for its citizens.

From stationary to directional transition: a case study in Doñana

ContextDoñana’s landscape is a mosaic of different types of transitions at different spatial and temporal scales. Among them, stationary transitions are relatively stable over time, while directional transitions involve the unidirectional movement of boundaries. The fiftieth anniversary of the Doñana National Park (SW Spain) provided a framework to test the transformation of a biotic transition from stationary to directional.ObjectivesThis study aimed to examine landscape changes along a stationary groundwater-dependent transition, the processes responsible for them, and the consequences for the biotic transition.MethodsThrough detailed photointerpretation, nine land use/land cover categories were mapped at four dates (1971, 1984, 2002, 2019) on a ca. 2 square km plot, and then changes analysed at three levels (interval, category, and transition) using Intensity Analysis. Potential causes including precipitation, groundwater levels, local management and changes in the surroundings were examined to understand the changes.ResultsJuniper woodland, spontaneous pines and mixed shrub categories showed the greatest gains and were most active. In the third interval (2002–19) largest transitions from pond-grassland to several terrestrial categories and the dead of heathlands indicate the encroachment of xeric communities into hygrophytic ones. Observed changes seem to be due to succession, forestry management and extrinsic drivers such groundwater overexploitation in the surroundings of the protected area.ConclusionsThe long-term study of this stationary transition shows the weakening of the factors that controlled its establishment, the loss of its constituent habitats due to groundwater withdrawal, and its conversion into a directional transition.

Soil Moisture Monitoring and Evaluation in Agricultural Fields Based on NDVI Long Time Series and CEEMDAN

The North China Plain is an important area for agricultural economic development in China. But water shortages, severe groundwater over-exploitation and drought problems make it difficult to exercise the topographic resource advantages of the plain. Therefore, the precise monitoring of soil moisture is of great significance for the rational use of water resources. Soil characteristics vary in natural farmland ecosystems, crops are constrained by multiple compound stresses and the precise extraction of soil moisture stress is a difficult and critical problem. The long time series was decomposed via complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) to obtain different intrinsic mode function (IMF) components, and the statistical descriptors of each component were calculated to realize the precise discrimination of soil moisture stress. A quantitative evaluation model of soil moisture was established, and the different noise addition ratios and modeling types were set respectively to investigate the optimal inversion model. The results showed that: (1) The reconstruction error of the CEEMDAN was small and almost 0; it had a high reconstruction accuracy and was more suitable for the decomposition of the long time series. The first two components, IMF1 and IMF2, were soil moisture stress subsequences, and it could effectively reflect the moisture stress situation. (2) The inversion model performed well when ε was 0.05 and the model type was quadratic, with a coefficient of determination R2 of 0.98, which gave a better fit and less error. (3) The overall soil moisture content in the study area was low, basically in the range of 6.9% to 15.7%, with the central part, especially the south-central part, being the most affected by soil moisture stress, and the overall impact of soil moisture stress showed a decreasing trend from February to May. The utilization of CEEMDAN further enhances the accuracy of soil moisture inversion in agricultural fields, realizing the effective application of remote sensing observation technology and time-frequency analysis technology in the field of soil moisture research.

Groundwater Level Dynamic Impacted by Land-Cover Change in the Desert Regions of Tarim Basin, Central Asia

Groundwater is essential to residents, ecology, agriculture, and industry. The depletion of groundwater impacted by climatic variability and intense human activities could threaten water, food, and socioeconomic security in arid regions. A thorough understanding of groundwater level dynamics and its response to land-cover change is necessary for groundwater management and ecosystem improvement, which are poorly understood in arid desert regions due to a scarcity of field monitoring data. In our study, spatiotemporal characteristics of groundwater level impacted by land-cover change and its relationship with vegetation were examined using 3-years in-situ monitoring data of 30 wells in the desert regions of Tarim Basin during 2019–2021. The results showed that the depth to groundwater level (DGL) exhibited obvious spatial and seasonal variations, and the fluctuation of DGL differed significantly among the wells. The cultivated land area increased by 1174.6, 638.0, and 732.2 km2 during 2000–2020 in the plains of Yarkand, Weigan-Kuqa, and Dina Rivers, respectively, mainly transferring from bare land and grassland. Annual average Normalized Difference Vegetation Index (NDVI) values increased with time during the period in the plains. DGL generally exhibited a weakly increasing trend from 2019 to 2021, mainly due to human activities. Land-cover change significantly affected the groundwater level dynamic. Generally, the groundwater system was in negative equilibrium near the oasis due to agricultural irrigation, was basically in dynamic equilibrium in the desert region, and was in positive equilibrium near the Tarim River Mainstream due to irrigation return water and streamflow. NDVI of natural desert vegetation was negatively correlated with DGL in the desert regions (R2 = 0.78, p < 0.05). Large-scale land reclamation and groundwater overexploitation associated with water-saving irrigation agriculture development have caused groundwater level decline in arid oasis-desert regions. Hence, controlling groundwater extraction intensity, strengthening groundwater monitoring, and promoting water-saving technology would be viable methods to sustainably manage groundwater and maintain the ecological environment in arid areas.

Land subsidence prediction in Zhengzhou's main urban area using the GTWR and LSTM models combined with the Attention Mechanism

In recent years, due to urbanization and human activities, groundwater overexploitation has become increasingly severe, resulting in some degrees of land subsidence and, consequently, causing a series of geological disasters and other environmental issues. Therefore, large-scale and high-precision land subsidence prediction is of great importance for the prevention and control of geological disasters. However, the existing prediction models and methods ignore the effects of the spatiotemporal non-stationary relationships between the influencing factors and the accumulated land subsidence, causing the poor accuracy of the predicted land subsidence results. In this context, a Geographically and Temporally Weighted Regression combined with the Long Short-Term Memory (LSTM)-multivariable and Attention Mechanism (AM) (GTWR-LSTMm-AM) was proposed to more accurately predict the deformation of time series land subsidence in this study. The small baseline subset-interferometric synthetic aperture radar (SBAS-InSAR) was used to reveal the temporal deformation information of Zhengzhou's main urban area, then the GTWR model was used to assess the spatiotemporal non-stationarity relationships between the accumulated land subsidence and its influencing factors monthly groundwater stability level, monthly precipitation and Normalized Difference Vegetation Index (NDVI) data, and to determine the corresponding weight matrix. In addition, we introduced an LSTM model with AM to extract key information from the time-series land subsidence data and adjusted the dynamic weights of the three selected influencing factors to predict the land subsidence in Zhengzhou's main urban area. The prediction accuracy R2 of the GTWR-LSTMm-AM model reaches 0.972, which is higher than 0.929 of the LSTMm model. The prediction accuracy RMSE is less than 3 mm and reaches 2.403 mm. In addition, we determined the importance of the impact factor on the subsidence results by randomly interrupting the impact factor time series, disclosuring that the monthly groundwater level contributed the most to the land subsidence in Zhengzhou's main urban area.

The alarming state of Central Chile's groundwater resources: A paradigmatic case of a lasting overexploitation

Ensuring water supply under climate change scenarios is a global concern, and groundwater resources play a crucial role. Aquifer depletion is a worldwide trend, and Chile is no exception. Through a statistical approach with strong hydrogeological criteria, the groundwater overexploitation phenomenon is studied in Central Chile, the most populated region in this mountainous country. With this purpose, we assess the evolution of groundwater levels and pumping between 1970 and 2020 by analysing 26,065 groundwater rights and 222 observation wells. Withdrawals increased from 498 hm3 in 1970 to 8883 hm3 in 2020. We recognised two general trends in groundwater levels: a quasi-steady state hydrodynamic regime pre-1988 and sustained decline post-1988, exacerbated since 2010 with the start of the Megadrought. Although groundwater recharge is expected to decrease during this severe drought, the declining trend strongly correlates with pumping but not with precipitation changes. Climate forcing is usually invoked to warrant the dramatic depletion of groundwater resources, but we demonstrated that all analysed aquifers have been overexploited since much earlier than 2010. Finally, the Chilean aquifers' overexploitation is a clear example of the consequences of prioritising the water offer over the water demand regulation, which hinders the United Nations' sustainable development goals accomplishment.

Explaining the change of virtual groundwater transfers from China's overexploited regions through full supply chains

Groundwater is under increasing pressure in China with unsustainable abstraction threatening eco-environment system and sustainable development. Yet it is not clear how virtual groundwater transfer through inter-provincial and international trades contributes to distant groundwater overexploitation over a period of time. This analysis traces groundwater abstraction from overexploited regions of China incorporated in the complete supply chain to final consumption, and examines drivers for dynamic changes of virtual groundwater transfers between 2007 and 2017 using the structural decomposition analysis. Groundwater use in four overexploited regions (i.e. North China Plain, Northeast China, hinterland North China and Xinjiang) were 88–91 billion m3 (about 85%–88% of national groundwater withdrawal). Inter-provincial virtual groundwater transfer presented an increasing trend with its share of total groundwater withdrawal increased from 36.4% to 45.4%, indicating an increasing reliance of regional final consumption on groundwater use beyond province boundaries. Structural decomposition analysis revealed that increasing receipt of commodities from overexploited regions was a major contributor to increasing reliance on virtual groundwater. Improved water use efficiency and consumption structure offset increasing virtual groundwater transfers from overexploited regions. The understanding gained in this study can be used by water managers and policy makers to improve the governance and management of groundwater resources.

Assessment of groundwater vulnerability for seawater intrusion using DRASTIC model in coastal area at Patuakhali District, Bangladesh.

Seawater intrusion is a growing concern for coastal regions in Bangladesh. Overexploitation of groundwater, low rainfall, a high rate of evaporation, rising sea level, cyclones, storm surges, and shrimp cultivation are the causes of seawater intrusion that polluted the groundwater near the coastal area. High values of EC, TDS, Na+, and Cl- ions in groundwater indicate the seawater intrusion. Piper's Trilinear and Durov diagrams of groundwater indicated that most gathered groundwater show predominantly Na-Cl-type of water. Based on the USSL diagram, it is observed that the salinity of the study area is medium to high and the alkalinity is medium to very high. Also, in view of the Wilcox outline, most of the samples in the area of interest are permissible to doubtful, and doubtful to unsuitable. Chloride is moderately correlated with Na+ (R2 = 0.590) and poorly correlated with (HCO3- + CO32-) (R2 = 0.128), which indicates seawater intrusion. According to a comparison of the levels of Fe and Mn in the groundwater of the study area with those recommended by the World Health Organization (WHO) and Department of the Environment (DOE), twenty-two out of thirty-one samples exceed the acceptable limit for Fe and thirty out of thirty-one samples fall within the acceptable limit for Mn. The calculated water quality index reveals that most samples are of low drinking water quality. The research area's poor water type is found in the north-central and southern parts. The WQI geographic variation map reveals that the study's water has a WQI of more than 100, making it unsuitable for consumption. The final seawater intrusion vulnerability map clearly identifies the moderate to highly vulnerable zone of the study area using DRASTIC index parameters. DRASTIC index parameters revealed that some portions of the northwestern part of the sample area show a moderately vulnerable zone. And the rest of the sampling area indicates the highly vulnerable zone.

Modelling the Spatial Distribution and Future Trends of Seawater Intrusion due to Aquaculture Activities in Coastal Aquifers of Nizampatnam, Andhra Pradesh

Coastal aquifers suffer from saltwater intrusion due to several natural and anthropogenic activities and they pose a severe problem in many coastal regions of India. Anthropogenic activities like saltwater aquaculture activities and salt pans are one of the major causes for saltwater intrusion into freshwater aquifers in coastal regions. Along with these activities, over-exploitation of fresh groundwater for domestic and agriculture purpose also leads to infiltration of saltwater into shallow freshwater aquifers. To address this effect, it is necessary to understand the spatial distribution and extent of the saltwater intrusion in coastal areas. In the present study, SEAWAT model is used to delineate the saltwater intrusion effect and predict the extent of saltwater intrusion resulting from anthropogenic activities in the Nizampatnam coastal area, Andhra Pradesh. The simulation was carried out for the period 2016 to 2018 revealing a change in the extent of the saltwater intrusion up to 2 km into the inland areas from the coast as well as in the vicinity of fishponds. Based on the hydrological conditions observed during the study period and leveraging the calibrated model, saltwater intrusion prediction was carried out for the next two decades. The results show that anthropogenic activities will lead to saltwater intrusion into freshwater aquifers up to 6 km into inland areas from coast at a rate of 200 m/year. Therefore, the sustainable management plans are essential for protecting the freshwater aquifers from the saltwater intrusion in the Nizampatnam coastal area.

Identifying hotspots of water table depth change by coupling trend with time stability analysis in the North China Plain

Many groundwater construction projects such as South-to-North Water Diversion Project (SNWDP) were conducted for controlling groundwater overexploitation in the North China Plain (NCP). However, more insight is required into the magnitude and distribution of water table depth (WTD) in time and space over the NCP. This study evaluated the variability and the hotspots of WTD based on 83 unconfined monitoring wells and took trend, breakpoint, and time stability into consideration. We found the average WTD of unconfined aquifer for the Southern Hebei Plain generally increased continuously from 1998 to 2020 in spite of the operation of the SNWDP since 2014. However, the rise rate of WTD slows down in recent years and the WTD has decreased in certain subregions. We further divided these groundwater wells into five groups: climb accelerating (Group 1), increase decelerating (Group 2), first rise then descend (Group 3), first descend then rise (Group 4), decrease decelerating (Group 5), and reduce accelerating (Group 6). Moreover, we found that the number of wells that divided into Group1 to Group 5 account for 15 %, 41 %, 25 %, 18 %, and 1 % of the total number of observation wells. The breakpoints of all the wells are from 2001 to 2017 and most of the breakpoints were found before 2014, which demonstrates that other groundwater management strategies implemented in the Southern Hebei Plain prior to the operation of the SNWDP plays a crucial part. The hotspots area for group 1 is mainly distributed in the north region of Shijiazhuang City, group 2 is in southern region of piedmont plain, group 3 is in northern region of Baoding and south-west region of Xingtai City, and group 4 is in Cangzhou City and eastern region of Xingtai City. The method and framework of this study can be applied in other regions suffering from groundwater depletion.