Over-extraction Of Groundwater Research Articles

Hydrogeochemical characterization and water quality evaluation for drinking and irrigation purposes of coastal aquifers of Middle Andaman

A comprehensive study to characterize the hydrogeochemistry of the region and the impact of saltwater intrusion on groundwater was conducted along the eastern coast of Middle Andaman of Andaman and Nicobar (A&N) Islands. The escalating population growth and intensified tourism activities have resulted in the over-extraction of groundwater. Seismic activities led to the opening of lineaments to the sea and the dissolution of limestone in the influence of seawater. 24 groundwater samples and 1 reference sample from sea were taken from various locations of middle Andaman. The analysis involved the determination of major cations, anions, and heavy metals using Inductively Coupled Plasma Optical Emission spectroscopy (ICP), spectrophotometry, and flame photometry. Furthermore, X-ray diffraction analysis, binary diagrams, Chloro-alkaline indices (CAI), Gibbs Plot, correlation matrix, Piper plot, Chadha’s plot and Principal Component Analysis (PCA) to the major ions data indicated rock-water interactions, strong correlations among alkali and alkaline earth metals, and interactions between seawater and carbonate minerals respectively. The water quality index indicated “very poor to unsuitable for drinking purposes” in 24% of the samples. Additionally, indices for irrigation suitability; total hardness (TH), residual sodium carbonate (RSC), and Magnesium adsorption ratio (MAR) were found to be detrimental for irrigation in 80%, 08%, and 12% of the water samples, respectively. These results highlight the importance of implementing effective water resource management techniques, such as groundwater extraction rates, adopting appropriate water treatment technologies to mitigate the adverse impacts of heavy metals, saltwater intrusion and maintain water quality for human consumption and agricultural use in the region.

Analysis on the spatiotemporal evolutions of groundwater hydrochemistry and water quality caused by over-extraction and seawater intrusion in eastern coastal China

The over-extraction of groundwater has resulted in seawater intrusion and the southward migration of the saltwater interface, gradually deteriorating the groundwater quality in the Weibei Plain. In this research, groundwater samples were gathered from 46 monitoring wells for shallow groundwater during the years 2006, 2011, 2016, and 2021. The hydrochemical features of regional groundwater and the factors influencing the issue were subjected to statistical analysis. Additionally, the assessment of spatiotemporal variations in groundwater quality was conducted using the customized entropy-weighted water quality index (EWQI) method. The relationship between groundwater over-extraction and the southward intrusion of the saltwater interface was compared and analyzed. The results of this paper revealed that the Weibei Plain has been in a state of long-term over-extraction of groundwater from 2000 to 2021, with an average annual over-extraction of 118.49 million m3. The groundwater depression cone areas in the northern part of the study area increased from 3,247.37 to 4,581.34 km2 from 2006 to 2021, with the center of the cone experiencing a drop in groundwater level from −22 to −85 m. The saltwater interface shifted southward by 711.71 km2 from 2006 to 2021. In groundwater, the high concentrations of TH, TDS, and Cl− were primarily related to the seawater intrusion, while higher concentrations of NO3− were mainly determined by frequent agricultural production, industrial wastewater, and domestic sewage discharges. The groundwater hydrochemical types in the study area transitioned from predominantly HCO3·Ca-Mg type in 2006 to HCO3-Na type and SO4·Cl-Ca·Mg type in 2021 due to seawater intrusion. The results of PCA and HCA show the effects of seawater intrusion, human activities, and rock weathering on groundwater hydrochemistry. The evaluation results based on the EWQI revealed that the average value of the samples in 2021 was 101.36, which belonged to Class IV water quality standards, representing the poorest water quality among the 4 years. The southward migration of the saltwater interface led to the deterioration of groundwater quality in the groundwater depression cone areas, which gradually worsened from 2006 to 2021. The maximum increase in EWQI value was 174.68 during the period, shifting from Class III water quality to Class V water quality. Groundwater quality remained relatively better in the western and southern regions which were less affected or unaffected by seawater intrusion. The results of the study can provide a certain reference value for the sustainable management of groundwater resources and the management of groundwater pollution and seawater intrusion in the Weifang City area in the future.

Origin and current activity of the Jiaocheng ground fissure, a 48 km long fissure in northern China

Since the mid to late 20th century, several regions in Northern China have had to contend with ground fissure disasters, with the FenWei basin and North China Plain being clear examples. The Jiaocheng ground fissure, which spans a total of 48 km in the FenWei basin, has caused severe damage to infrastructure along its path. In recent years, the local activity of the Jiaocheng ground fissure has worsened. Field investigations, mapping, trenching, geophysical surveys and other methods have been used to determine the origin mechanism and current activity characteristics of the Jiaocheng fissure. The Jiaocheng ground fissure has a general orientation stretching 48 km in the NE-NEE direction, inclining towards the SE. The Jiaocheng ground fissure involves horizontal tension and vertical dislocation, with segmented activity on the surface, with the most intense activity observed in the northern Qingxu section. In profile, it displays characteristics of synsedimentary faults and primary-secondary fissure combinations. The activity of the Jiaocheng fault underlies the occurrence of the Jiaocheng ground fissure. Over-extraction of groundwater has exacerbated the fissure activity. Recently, the Jiaocheng ground fissure has displayed localized intensification and the emergence of new fissures stretching towards the north. This has been linked to heightened tectonic activity in the northern region of the Taiyuan basin.

Analyzing river disruption factors and ecological flow in China's Liu River Basin amid environmental changes.

Water resources variability and availability in a basin affect river flows and sustain river ecosystems. Climate change and human activities disrupt runoff sequences, causing water environmental issues like river channel interruptions. Therefore, determining ecological flow in changing environments is challenging in hydrological research. Based on an analysis of long-term changes in hydrological and meteorological variables and interruption conditions in the semi-arid Liu River Basin (LRB), this study summarizes the controlling factors of river interruption at different temporal and spatial scales and proposes a framework to determine ecological flow under changing environments. Hydrological model and the monthly optimal probability distribution were used to determine the optimal ecological runoff of LRB. The results showed that from 1956 to 2017, precipitation and potential evapotranspiration in the basin showed no significant decreasing trend, but the streamflow significantly decreased, and the downstream interruption worsened, with an average annual interruption duration of 194days at Xinmin Station from 1988 to 2017. The controlling factors of river interruption are as follows: (1) soil and water conservation measures in the upstream significantly reduce the runoff capacity; (2) the operation mode of the controlling reservoir in the middle reaches changes from "all-year discharge" to "winter storage and spring release" to "combined storage and supply," severing the hydraulic connection between upstream and downstream; and (3) siltation in the downstream river channel coupled with over-extraction of groundwater increases the seepage capacity of the river. The monthly ecological flow of Naodehai Reservoir was determined by considering the monthly seepage losses after reconstructing the natural runoff using the SWAT model and determining the optimal probability distribution function for monthly runoff. The findings are important for downstream LRB ecological restoration and for determining the ecological flow of other river basins in changing environments.

Getting Ahead of the Game: Experiential Learning for Groundwater Governance in Ethiopia

Groundwater management is highly complex, with many users sharing the same resource often with limited understanding of their interconnectedness. Behavioral experiments (games) that simulate real-life common-pool resource use have shown promise as an experiential learning tool for improving resource governance. This study pilots an experiential learning intervention in Ethiopia using a groundwater game to help raise awareness of groundwater over-extraction and improve understanding of the importance of collective action in governance. In the Meki River catchment in Ethiopia, small-scale irrigation is expanding, but overextraction and competition over groundwater have not yet reached alarming levels. The groundwater game, adapted from India and including the addition of a rule-making round, was played in 15 villages with 30 groups. The game was accompanied by subsequent community-wide debriefing in each village to reflect on the experience and lessons learned, which stimulated discussions about groundwater governance. We surveyed participants to capture individual mental models regarding groundwater use and management, as well as any immediate learning effects. Focus group discussions in each village prior to the intervention and again six months after the intervention assessed possible lasting effects. The findings indicate cognitive, normative and relational learning, including increased understanding of groundwater dynamics (such as the joint effect of diverse water uses and users), the importance of collective action in resource management, and the benefits of communication. We find gendered differences in decision-making about resource extraction in the game and development of group-level resource management, confirming the need for gender-responsive approach to sustainable groundwater management interventions. We discuss community-wide learning and institution-building, and considerations for future intervention designs. We recommend embedding experiential learning, facilitated by local extension officers and other practitioners, in intervention packages that include both technical assistance on water-conserving technologies and groundwater management approaches and support in building communities’ institutional capacity.

Distribution and Origins of Hardness in Shallow and Deep Groundwaters of the Hebei Plain, China

Elevated hardness concentrations in groundwater have become a noteworthy concern in recent decades because long-term drinking of groundwater with high levels of hardness is an important factor resulting in chronic kidney diseases. In this study, the distribution and origins of groundwater total hardness (TH) in various sub-plains and different land-use areas of the Hebei Plain (HBP) were investigated. A total of 445 groundwater samples in the HBP were collected once in 2021, and twelve chemical parameters, including TH in groundwater, were analyzed. Results showed that TH-rich (>450 mg/L) shallow groundwater in both the central and littoral plains was more than twice that in the Piedmont plain. Similarly, TH-rich deep groundwater accounted for about 18% in the central plain but was negligible in the Piedmont plain. In the Piedmont plain, TH-rich shallow groundwater in urban areas was twice or more than in other land use types. By contrast, both TH-rich shallow and deep groundwaters in agricultural areas in the central plain were higher than those in rural areas. This was opposite to TH-rich shallow groundwater in the littoral plain. In the Piedmont plain, TH-rich shallow groundwater was mainly attributed to water-rock interaction, groundwater over-extraction, and the infiltration of domestic sewage and animal waste. In the central plain, both TH-rich shallow and deep groundwaters likely ascribed to the evaporite dissolution and seawater intrusion. By contrast, the leaching of agricultural fertilizers resulting in the dissolution of Ca-rich and Mg-rich minerals in the vadose zone was mainly responsible for the occurrence of TH-rich shallow groundwater in the littoral plain. Therefore, in order to limit elevated hardness concentrations in groundwater in the HBP, limiting shallow groundwater extraction and strengthening the supervision of the domestic sewage and animal waste in the Piedmont plain are recommended. Besides, restricting the use of nitrogenous fertilizers in the littoral plain is also recommended.

Estimation of land subsidence using coupled particle swarm optimization and genetic algorithm: The case of Damghan aquifer

Abstract Land subsidence, which is mainly caused by over-extraction of groundwater, is one of the most important problems in arid and semi-arid regions. In the present study, seven factors affecting the land subsidence, i.e., types of subsoil, land use, pumping, recharge, thickness of the plain aquifer, distance to the fault, and groundwater depletion were considered as input data for the ALPRIFT framework and intelligence models to map both Subsidence Vulnerability Index (SVI) and prediction of land subsidence, respectively. The hybrid of particle swarm optimization (PSO) and genetic algorithm (GA) (Hybrid PSO-GA) was then used to optimize the weights of the input layers and the estimation of the land subsidence. The capability of the PSO-GA at predictions of land subsidence compared with the typical GA model, and Gene Expression Programming (GEP). The statistical indices R2, RMSE, and MAE were used to assess the accuracy and reliability of the applied models. The results showed that the Hybrid PSO-GA model had R2, RMSE, and MAE equal to 0.91, 1.11 (cm), and 0.94 (cm), respectively. In comparison with the GA, and GEP models, the Hybrid PSO-GA model improved the prediction of land subsidence and reduced RMSE by 24.30 and 16.80%, respectively.

Risks in the current groundwater regulation approach in the Beetaloo region, Northern Territory, Australia

ABSTRACT Plans are underway to greatly increase rates of groundwater extraction from the Northern Territory’s Cambrian Limestone Aquifer (CLA), particularly above the Beetaloo sub-basin, to allow expansion of shale gas and agricultural industries. We analyse current groundwater regulations in the NT, and the state of knowledge regarding key aspects of the region’s hydrogeology and values sustained by groundwater. We find that the current rules governing the administration of groundwater licencing in areas without a Water Allocation Plan (WAP) – the Top End and Arid Zone rules – are poorly suited to protect ecological, Indigenous socio-cultural and other water use values. These rules (as currently applied) allow the depletion of substantial groundwater storage in areas that fall within the ‘arid zone’ (as defined in NT policy). Such depletion risks the reduction or loss of groundwater flows to ecosystems and stygofauna habitat and reduced throughflow of groundwater between different regions, within the highly connected CLA system. This may disrupt water flows that sustain local livelihoods and those that are integral to Indigenous peoples’ beliefs and cultural practices. The new WAP that applies over much of the Beetaloo sub-basin (Georgina-Wiso WAP) is also deficient in key areas. It has failed to comply with national water policy, in that no substantive steps have been taken to understand Indigenous cultural and ecological values sustained by groundwater prior to setting an Estimated Sustainable Yield. A more precautionary, inclusive approach to determining groundwater regulations would involve a) setting of conservative water extraction limits combined with trigger levels for ecosystem protection and b) co-management in partnership with Aboriginal peoples, with both consultation and decision-making processes that recognise their inherent rights and interests in water. This will be critical to avoiding long-term environmental and socio-cultural harm from over-extraction of groundwater.

Assessment of Active Ground Subsidence in the Dibrugarh and Digboi Areas of Assam, Northeast India, Using the PSInSAR Technique

Ground deformation on a regional to local scale is the consequence of a wide range of natural processes such as tectonic and anthropogenic activities. Globally, the over-extraction of groundwater and hydrocarbon exploitation are the primary causes of ground subsidence. The current study demonstrates regional scale ground subsidence analysis of the Dibrugarh and Digboi regions of Brahmaputra alluvial plain, Assam, Northeast India. To understand the ongoing surface deformation satellite base, the RADAR technique has been applied using SENTINEL-1A data, which were acquired between 15 October 2015 to 25 January 2022. The assessment carried out via the time series analysis of the radar data suggests that the Dibrugarh area is subsiding at a rate of ~5 mm/yr, whereas the Digboi is deforming at a much faster rate (±22 mm/yr) than Dibrugarh. The presence of active faults in the subsurface and associated deformation is another reason for active ground subsidence. The outcomes of the current study validate that the study area is currently undergoing active subsurface deformation caused by both endogenic as well as exogenic processes. Furthermore, our Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR) and satellite-based analysis suggest that the over-exploitation of the natural resources is enhancing the rate of deformation in the Brahmaputra alluvial plain in the northeast of India.

Safe Groundwater Level Estimation in Pingtung Plain, Taiwan

The groundwater resources in the Pingtung Plain are crucial water sources in southern Taiwan. However, they have been significantly impacted by climate change, resulting in changes in groundwater quality and quantity in the region. To effectively manage groundwater extraction, this study utilized runs theory to analyze the safe groundwater levels at six groundwater level observation stations located in the proximal fan, mid fan, and distal fan areas of the Pingtung Plain. The methodology involved dividing the range between the maximum and minimum groundwater levels at each station into 20 equal intervals. The groundwater levels were then sorted in ascending order, and the cumulative frequency percentiles of groundwater levels in each interval were calculated to determine the truncation levels for runs theory. Subsequently, the groundwater over-extraction duration and severity were computed. By comparing the results with the groundwater management levels set by the Water Resources Agency of the Ministry of Economic Affairs, it was found that the safe groundwater levels in the proximal fan and distal fan areas were the average of observation data plus 0.5 times the standard deviation. The over-withdrawn duration for these areas was approximately 8 to 10 months and 8 months, respectively. In the mid fan area, the safe groundwater level was based on the average of observation data, and the over-withdrawn duration ranged from 6 to 9 months.

Water Requirements and Comprehensive Benefit Evaluation of Diversified Crop Rotations in the Huang-Huai Plain

An intensified farming system can significantly increase crop productivity but can also cause major groundwater overdraft for irrigation and the loss of crop diversity. It is imperative to develop alternative crop rotations beyond the simplified conventional winter wheat–summer maize (W–M) rotation for alleviating the groundwater over-extraction in China’s Huang-Huai Plain. This study systematically quantified crop water requirement (ETc) and irrigation water requirement (ETaw) of eight crops from 2013 to 2018 based on the SIMETAW model applied to the Shangqiu area in the Huang-Huai Plain. Fourteen crop rotations (CI (i.e., crop harvests per rotation cycle year) 1.5 or 2) were constructed based on the ROTAT model. Results showed that compared to W–M rotation, the alternative rotations (CI = 1.5) significantly reduced the annual ETc in wet, normal, and dry years by 9–21%. Replacing winter wheat in the double cropping system did not significantly decrease annual ETc. Wheat–soybean rotation had similar annual ETc and ETaw accompanied by higher economic output and equivalent yield about 1.2 times, with 9% more protein output than the W–M rotation. There were eight crop rotations having greater comprehensive evaluation index (CEI) than W–M rotation by Entropy-TOPSIS when considering 10 indicators including water requirements, yield, economic benefits, water use efficiency, energy, and nutritional values. Spring potato–summer soybean had the highest CEI of 0.627. Sweet potato and potato showed advantages when included in rotations by increasing yield. “Wheat–soybean”-based rotations (CI = 1.5) also performed well in profitability and protein output. Replacing summer maize with soybean is promising for profitability and nutrition output without increasing irrigation requirements. Therefore, decreasing the cropping index, or involving soybean or sweet potato in rotations can be a useful way to improve sustainable land use, save water, and ensure food products in this water stressed region.

Groundwater Use Habits and Environmental Awareness in Ca Mau Province, Vietnam: Implications for Sustainable Water Resource Management

The Vietnamese Mekong Delta including Ca Mau province (CMP) is seriously affected by land subsidence. Groundwater over-extraction is considered to be a major driver for this process. To address the reduction of groundwater (GW) extraction as a potential counter measure for further subsidence, this study focuses on understanding the importance of GW in people's life and water using habits as well as their awareness with current environmental problems in Ca Mau. Therefore, GW sampling campaigns and surveys were conducted in all 9 districts of Ca Mau province in 2019 and 2020. The analyzed water samples showed a connection with information from questionnaires and created a general picture of water using habits. GW plays an important role in people's lives, it is used for washing, cooking, drinking and other activities. People use GW for different purposes depending on their perception of water quality. For important and direct health related purposes, such as cooking or drinking, people prepare to treat water more carefully or choose another alternative water resource. The analytical approach to evaluation results based on viewpoints from general to detail helped to dig deeper into people's stories to explain research results with their behavior in each situation. When people are dependent on GW and have no option to use alternative water resources, the importance level of GW in their life increases and their awareness of GW over-extraction becomes less. If people have another water source to use such as tap water (TW), habits of using GW change. This opens up the idea that a potential alternative water will reduce the dependence of people on GW and protect GW from over-exploitation. Besides, people in Ca Mau do not have much awareness of land subsidence or the reason leading to environmental problems. Therefore, raising the awareness of people by well-design education campaigns should be strongly considered.

Impact of limestone caves and seawater intrusion on coastal aquifer of middle Andaman

Seawater intrusion has become a common problem in coastal and island aquifers with the rise in climate change that greatly affects the majority of developing countries. The island hydrology is very complex and associated with a unique set of environmental characteristics with the dynamic interaction of groundwater, surface water, and seawater. Further, Sea level rise, erratic rainfall, and over-extraction of groundwater triggered salt-water intrusion. A study on seawater intrusion and the effect of limestone caves on groundwater was carried out in middle Andaman using a combination of ionic ratios of major ions. A total of 24 samples and a reference sample from the sea were collected and analysed using ICP, spectrophotometer, and flame photometer. A combination of 10 ionic ratios Cl/HCO3, Ca/(HCO3 + SO4), (Ca + Mg)/Cl, Ca/Mg, Ca/Na, Cl/(SO4 + HCO3), Ca/SO4, K/Cl, Mg/Cl, and SO4/Cl was used to assess the dissolution of limestone minerals and the level of saltwater intrusion into groundwater. The geospatial method was used to extract and combine all the hydrogeochemical parameters and ionic ratios in the GIS platform. Durov plot was used for the interpretation of groundwater chemistry and the identification of natural processes controlling the hydrogeochemistry of the area. The dominance of Ca-HCO3 and Na-HCO3 was confirmed in 48% and 24% of the sample respectively. The equiline graph of chloride with other major ions showed the enrichment of alkali and alkaline earth metal salt in groundwater. Schoeller's diagram depicted the dominance of Cl, Ca, and the sum of CO3 and HCO3 in seawater near Mayabunder. The lower concentration of Na with respect to Cl (64%) and Ca (100%) showed the presence of a reverse ion exchange process. Further, the correlation matrix showed a strong relationship between Cl, K, Ca, and Na. The analysis of X-ray diffraction of the rock samples confirmed the presence of limestones such as Aragonite, Calcite, Chlorite, Chromite, Dolomite, Magnetite, and Pyrite in the study area. The integration of ionic ratios showed moderately affected and slightly affected saline regions in 44% and 54% of the region respectively. Finally, the role of tectonic activities and active lineaments connected to the sea was found to play a major role in the intrusion of seawater where interconnected faults created an opening for surface water to recharge groundwater leading to the deep aquifer.

Impact of clayey sediment compaction on pore water evolution and the release of iron

The groundwater contaminants caused by the clayey sediment compaction have been reported in numerous groundwater overextraction regions. But little is known about the impact of compaction on the evolution of pore water compacted from the clayey sediments. In this study, we collected clayey sediments and conducted a low-pressure indoor experiment to identify the pore water evolution and iron releasing mechanism. Pressure demonstrates a significant influence on the release and mobilization of iron in pore water and clayey sediments. Initially, Fe2+ concentration depletion in pore water is regulated by the reduction of Fe(III) (oxy) hydroxides and precipitation with S(-II) producing Fe–S phases. Subsequently, the increase of Fe2+ with the increased pressure is attributed to the transformation of FeS to FeS2. In the final stage of the pressure experiment, more formation of FeS2 and dissolution of siderite result in the fluctuation of Fe. In addition, a release of the trace metals (Fe, Mn, Cr, Cu, Ni and Zn) detected in pore water can be what creates a potential contaminant threat in the adjacent aquifers. The compaction of the clayey sediments results in a decrease of the water content and releases the pore water into the adjacent aquifers. This study reveals the pore water evolution, highlights the complex biogeochemical reactions of iron during clayey sediments compaction and reinforces the importance of clayey sediments compaction for the aquifers water quality.

Machine learning based downscaling of GRACE-estimated groundwater in Central Valley, California

California's Central Valley, one of the most agriculturally productive regions, is also one of the most stressed aquifers in the world due to anthropogenic groundwater over-extraction primarily for irrigation. Groundwater depletion is further exacerbated by climate-driven droughts. Gravity Recovery and Climate Experiment (GRACE) satellite gravimetry has demonstrated the feasibility of quantifying global groundwater storage changes at uniform monthly sampling, though at a coarse resolution and is thus impractical for effective water resources management. Here, we employ the Random Forest machine learning algorithm to establish empirical relationships between GRACE-derived groundwater storage and in situ groundwater level variations over the Central Valley during 2002–2016 and achieved spatial downscaling of GRACE-observed groundwater storage changes from a few hundred km to 5 km. Validations of our modeled groundwater level with in situ groundwater level indicate excellent Nash-Sutcliffe Efficiency coefficients ranging from 0.94 to 0.97. In addition, the secular components of modeled groundwater show good agreements with those of vertical displacements observed by GPS, and CryoSat-2 radar altimetry measurements and is perfectly consistent with findings from previous studies. Our estimated groundwater loss is about 30 km3 from 2002 to 2016, which also agrees well with previous studies in Central Valley. We find the maximum groundwater storage loss rates of −5.7 ± 1.2 km3 yr−1 and -9.8 ± 1.7 km3 yr−1 occurred during the extended drought periods of January 2007–December 2009, and October 2011–September 2015, respectively while Central Valley also experienced groundwater recharges during prolonged flood episodes. The 5-km resolution Central Valley-wide groundwater storage trends reveal that groundwater depletion occurs mostly in southern San Joaquin Valley collocated with severe land subsidence due to aquifer compaction from excessive groundwater over withdrawal.

Combining the classic vulnerability index and affinity propagation clustering algorithm to assess the intrinsic aquifer vulnerability of coastal aquifers on an integrated scale

In the northern plains of Laizhou City, groundwater quality suffers dual threats from anthropogenic activities: seawater intrusion caused by overextraction of fresh groundwater, and vertical infiltration of agricultural pollutants. Groundwater management requires a comprehensive analysis of both horizontal and vertical pollution in coastal aquifers. In this paper, Intrinsic Aquifer Vulnerability (IAV) was assessed on an integrated scale using two classic IAV models (DRASTIC and GALDIT) separately based on a GIS database. Hydrogeological parameters from two classic IAV models were clustered using affinity propagation (AP) clustering algorithm, and silhouette coefficients were used to determine the optimal classification result.In our application, the objects of the AP algorithm are 3320 units divided from the whole study area with 500 m*500 m precision. A comparison of all four outputs in AP-DRASTIC shows that the clustering results of the 4-classification yielded the best silhouette coefficient of 0.406 out of all four. Cluster 4, which comprises 21% of the area, had relatively low level of groundwater contamination, despite its high level of vulnerability as indicated by the classic DRASTIC index. In the second level of vulnerability Cluster 3, 53.8% of all water samples were found to be contaminated, indicating a greater level of nitrate contamination. With respect to AP-GALDIT, the silhouette coefficient for result 7-classification reaches the highest value of 0.343. There was a high level of vulnerability identified in Clusters 2, 4 and 5 (34.7% of the study area) relating to the classic GALDIT index. The concentration of chloride in all water samples obtained in these areas was extremely high. Groundwater management should be addressed by AP-DRASTIC results on anthropogenic activity/contamination control, and by AP-GALDIT results on groundwater extraction limitation. Overall, this method allows for the evaluation of IAV in other coastal areas on an integrated scale, facilitating the development of groundwater management strategies based on a better understanding of the aquifer's essential characteristics.

Assessment of Land Deformation and the Associated Causes along a Rapidly Developing Himalayan Foothill Region Using Multi-Temporal Sentinel-1 SAR Datasets

Land deformation has become a crucial threat in recent decades, caused by various natural and anthropogenic activities in the environment. The seismic land dynamics, landslides activities, heavy rainfall resulting in flood events, and subsurface aquifer shrinkage due to the excessive extraction of groundwater are among the major reasons for land deformation, which may cause serious damage to the overall land surface, civil infrastructure, underground tunnels, and pipelines, etc. This study focuses on preparing a framework for estimating land deformation and analyzing the causes associated with land deformation. A time-series SAR Interferometry-based technique called PsInSAR was used to measure land deformation, using Sentinel-1 datasets from 2015 to 2021 by estimating land deformation velocities for this region. The obtained PSInSAR deformation velocity results ranged between −4 mm to +2 mm per year. Further, land use land cover (LULC) changes in the area were analyzed as an essential indicator and probable cause of land deformation. LULC products were first generated using Landsat-8 images for two time periods (2015, 2021), which were then evaluated in accordance with the deformation analysis. The results indicated an increase in the built-up areas and agricultural cover in the region at the cost of shrinkage in the vegetated lands, which are highly correlated with the land subsidence in the region, probably due to the over-extraction of groundwater. Further, the outer region of the study area consisting of undulating terrain and steep slopes also coincides with the estimated high subsidence zones, which could be related to higher instances of landslides identified in those areas from various primary and secondary information collected. One of the causes of landslides and soil erosion in the region is identified to be high-level precipitation events that loosen the surface soil that flows through the steep slopes. Furthermore, the study region lying in a high seismic zone with characteristic unstable slopes are more susceptible to land deformation due to high seismic activities. The approach developed in the study could be an useful tool for constant monitoring and estimation of land deformation and analysis of the associated causes which can be easily applied to any other region.

Closing the irrigation water productivity gap to alleviate water shortage in an endorheic basin

Closing the irrigation water productivity (IWP) gap is an effective approach to alleviating water deficits and ensuring food security. However, few studies have attempted to quantify the IWP gap and the potential benefits of closing it. This study adopted the Heihe River Basin, the second-largest inland basin in China, as a typical study area. The aims of this study were to: (1) assess the positive achievements and potential risks triggered by the Heihe Ecological Water Diversion Project (EWDP) according to multi-source and multi-scale measured data; (2) analyze potential approaches to improve the IWP and quantify the potential benefits that can be achieved by closing its IWP gap. The results of this study indicated that the EWDP effectively reallocated surface water resources, replenished groundwater in the lower reaches, and facilitated the recovery of oases and economic development in the downstream regions. However, this project has indirectly led to an imbalance in the groundwater resource between the middle and lower reaches, resulting in decline in groundwater levels and degradation of local vegetation in the midstream regions. In addition, the expansion of cultivated land in the midstream and downstream oases has resulted in the deterioration of farmland environment. The water transfer resulted in a deceleration in the growth of IWP from 2.44 % to 1.15 %, and the existing IWP gap was 1.43 kg/m3 between 1984 and 2017. This study predicted a future increase in the IWP to 2.01 kg/m3 with a reduction in the gap to 0.45 kg/m3 while maintaining food production. The potential for conserving water in the Heihe agricultural region can reach 552 million m3 by reducing the planting area by 10 %, improving irrigation water use efficiency by 20 %, maintaining existing agricultural film inputs, and reducing fertilizer application by 10 %. Following the research recommendations can greatly alleviate the agricultural water shortage and over-extraction of groundwater in the middle reaches and ensure meeting ecological water demand in the lower reaches. This study can act as a reference for sustainable management of an endorheic basin.

Monitoring Land Subsidence: The Challenges of Producing Knowledge and Groundwater Management Indicators in the Bangkok Metropolitan Region, Thailand

Multiple major coastal cities face the threat of sea level rise with global climate change. This vulnerability can be further exacerbated by local contexts of urbanization and flood management. Land subsidence caused by groundwater over-extraction has long been identified as a factor that exposes cities to the threat of submergence through its interaction with the sea’s tidal regime or a river basin’s precipitation pattern and flood regime. Decision-making in regards to environmental issues such as land subsidence ultimately relies on monitoring data to frame the problem and formulate policies accordingly. Thus, in examining how subsidence has been shaped into a scientific reality in the Bangkok Metropolitan Region, this article reviews the limits and uncertainties of subsidence monitoring tools and their associated indicators for risk management (safe yield, piezometric level, and subsidence rate). Our analysis of existing technical reports, supported by interviews conducted with key actors involved in the processes of knowledge production and policy-making, has pointed out how such uncertainties give way to varied interpretations of these indicators, which continue to fuel the debate concerning the establishment of a safe yield for groundwater management. Furthermore, our research has also revealed that the monitoring of land subsidence has been receiving less priority due to institutional challenges within concerned governmental agencies. Ultimately, we argue that in order to use the resource sustainably, it is crucial to keep monitoring groundwater overdraft in the neighboring provinces of Bangkok to diligently anticipate long-term flooding risks associated with the changing hydrogeological regime of the delta.

Irrigation plays significantly different roles in influencing hydrological processes in two breadbasket regions

Agriculture is a major water user, especially in dry and drought-prone areas that rely on irrigation to support agricultural production. In recent years, the over-extraction of groundwater, exacerbated by climate change, population growth, and intensive agricultural irrigation, has led to a drop in water levels and influenced the hydrological cycle. Understanding changes in hydrological processes is essential for pursuing water sustainability. This study aims to estimate the amount and impact of irrigation on hydrological processes in two breadbasket regions, Jing-Jin-Ji (JJJ), China, and northern Texas (NTX), US. We used the Soil and Water Assessment Tool (SWAT) to explore spatiotemporal variations of irrigation from 2008 to 2013 and compared changes in hydrological processes caused by irrigation. The results indicated that deficit irrigation is more common in JJJ than in NTX and can reduce approximately 50 % of irrigation water use in areas with intensively irrigated cropland. The applied irrigation varies less over time in NTX but fluctuates in JJJ. Compared with NTX, the higher irrigation intensity in JJJ results in a more significant change in downstream peak streamflow of around 6 m3/s. Moreover, the difference in crop growing seasons can lead to different impacts of irrigation on hydrological processes. For example, the percentage change of surface runoff under real-world relative to the no-irrigation scenario was the greatest, around 40 %, in JJJ and NTX. However, the peak change occurred at different times, with the nearing maturity of winter wheat in May in JJJ and corn in August in NTX. The great potential to reduce groundwater extraction by adopting water conservation irrigation techniques calls for policies and regulations to help farmers shift towards more sustainable water management practices.