Excessive Groundwater Research Articles

Tectonic Control of Aseismic Creep and Potential for Induced Seismicity Along the West Valley Fault in Southeastern Metro Manila, Philippines

Vertical creep along 15 ground ruptures within a 15 km long and 1.5 km wide zone has been occurring along the southeastern part of Metro Manila. Though the unusually high rates of vertical slip point to excessive groundwater withdrawal as the trigger, the evidence presented herein indicates that these may not be simple irregular subsidence fissures. Tectonic control of creep along these traces is suggested by the following: the occurrence of some of these ground ruptures along pre-existing scarps that coincide with topographic and lithologic boundaries, the left-stepping en echelon pattern of surface rupturing, and the distribution of the creeping zone within the dilational gap of the dextral strike-slip West Valley Fault (WVF). Furthermore, interpretation of an exposure across one of the creeping faults indicates reactivation by creep of a pre-existing tectonic fault zone. The paleoseismic evidence also suggests that the pre-creep slips are coseismic and dominantly strike-slip. Recognizing the occurrence of coseismic slip preceding aseismic creep is a primary consideration in assessing the potential of the WVF’s creeping segment and its adjacent segments in generating earthquakes. Tighter groundwater extraction regulations may be necessary to avoid exacerbating the effects of vertical ground deformation and the occurrence of induced seismicity.

Evaluating pile foundation design due to groundwater level lowering

In Viet Nam, ground subsidence has been occurring at an alarming rate, raising concerns for pile foundation design. This issue is primarily caused by excessive groundwater extraction for water supply, irrigation, aquaculture, and other uses. Thus, in this study, the evaluation of pile capacity due to groundwater level (GWL) lowering as a preliminary guideline for structures is proposed. This study analyzed different cases of GWL lowering from 0 m to 2 m, and pile size varied from 18 x 18 cm to 45 x 45 cm, to evaluate the allowable bearing capacities for single piles and pile groups. The results indicated that when lowering the GWL from 0 to 2 m, the allowed bearing capacity varied by 5.75–174.70 tons for single piles and 11.95–808.18 tons for pile groups. Besides, when the pile size increased, the bearing capacity increased in the range of 6.38–41.46 tons (size 18 x 18 cm) to 16.30–174.70 tons (size 45 x 45 cm) for a single pile and 11.95–191.81 tons (size 18 x 18 cm) to 33.49–808.18 tons (size 45 x 45 cm). The result of this study underscores the significance of predicting the bearing capacity of pile foundations due to the variation in groundwater level.

A robust multi-model framework for groundwater level prediction: The BFSA-MVMD-GRU-RVM model

Groundwater level prediction is critical for environmental protection and agricultural planning. Accurate predictions help manage risks associated with excessive groundwater extraction and land subsidence. This study introduces a novel model combining multivariate variational mode decomposition (MVMD), gated recurrent unit (GRU), and relevance vector machine (RVM), along with the Boruta feature selection algorithm (BFSA), for precise groundwater level forecasting. The model operates in several stages. First, BFSA selects the most informative features as input data. Next, the MVMD method decomposes the time series of these features. The GRU model then extracts crucial information from these decompositions. Finally, the extracted data is fed into the RVM model to predict groundwater levels one month ahead in Iran's Bastam Plain. To assess the model's accuracy, multiple error indices were employed. The MVMD-GRU-RVM model outperformed other models, improving the testing Nash–Sutcliffe Efficiency and mean absolute error by 24–31 % and 6–61 %, respectively. Additionally, it enhanced R2 values of the MVMD-CNN, MVMD-RNN, MVMD-MLP, and MVMD-RBFNN models by 1.0–3.33 %. These results demonstrate that the MVMD-GRU-RVM model significantly improves groundwater level prediction accuracy. The key points of the paper are the successful effectiveness of MVMD in processing non-stationary time series and improving the predictive performance of the models, as well as the high ability of the GRU model in data feature extraction. The study also shows that the novel model can provide outputs with lower uncertainty.

Application of bagging and boosting ensemble machine learning techniques for groundwater potential mapping in a drought-prone agriculture region of eastern India

Groundwater is a primary source of drinking water for billions worldwide. It plays a crucial role in irrigation, domestic, and industrial uses, and significantly contributes to drought resilience in various regions. However, excessive groundwater discharge has left many areas vulnerable to potable water shortages. Therefore, assessing groundwater potential zones (GWPZ) is essential for implementing sustainable management practices to ensure the availability of groundwater for present and future generations. This study aims to delineate areas with high groundwater potential in the Bankura district of West Bengal using four machine learning methods: Random Forest (RF), Adaptive Boosting (AdaBoost), Extreme Gradient Boosting (XGBoost), and Voting Ensemble (VE). The models used 161 data points, comprising 70% of the training dataset, to identify significant correlations between the presence and absence of groundwater in the region. Among the methods, Random Forest (RF) and Extreme Gradient Boosting (XGBoost) proved to be the most effective in mapping groundwater potential, suggesting their applicability in other regions with similar hydrogeological conditions. The performance metrics for RF are very good with a precision of 0.919, recall of 0.971, F1-score of 0.944, and accuracy of 0.943. This indicates a strong capability to accurately predict groundwater zones with minimal false positives and negatives. Adaptive Boosting (AdaBoost) demonstrated comparable performance across all metrics (precision: 0.919, recall: 0.971, F1-score: 0.944, accuracy: 0.943), highlighting its effectiveness in predicting groundwater potential areas accurately; whereas, Extreme Gradient Boosting (XGBoost) outperformed the other models slightly, with higher values in all metrics: precision (0.944), recall (0.971), F1-score (0.958), and accuracy (0.957), suggesting a more refined model performance. The Voting Ensemble (VE) approach also showed enhanced performance, mirroring XGBoost's metrics (precision: 0.944, recall: 0.971, F1-score: 0.958, accuracy: 0.957). This indicates that combining the strengths of individual models leads to better predictions. The groundwater potentiality zoning across the Bankura district varied significantly, with areas of very low potentiality accounting for 41.81% and very high potentiality at 24.35%. The uncertainty in predictions ranged from 0.0 to 0.75 across the study area, reflecting the variability in groundwater availability and the need for targeted management strategies.In summary, this study highlights the critical need for assessing and managing groundwater resources effectively using advanced machine learning techniques. The findings provide a foundation for better groundwater management practices, ensuring sustainable use and conservation in Bankura district and beyond.

Identifying hidden groundwater reserves: GIS advances and multi-criteria decision analysis for enhanced potential assessment

The aquifer system may become susceptible as a result of excessive groundwater extraction without regard for scientific principles. This study evaluates the Groundwater Potential (G.P.) using multicriteria decision analysis (MCDA) and geospatial modelling. Here in MCDA, the G.P. is measured using Remote Sensing (R.S.) and Geographic Information System (GIS), together with Analytical Hierarchical Process (AHP), Fuzzy Analytical Hierarchical Process (FAHP), and Best Worst Method (BWM). Analysis and model creation took into account 15 groundwater affecting elements that affect the G.P. Groundwater Potential Zones (GPZs) in Cachar District, India varied by the following percentages: 46.97%, 37.41%, and 15.62% for AHP; 46.13%, 40.92%, and 12.95% for FHP; and 50.65%, 36.51%, and 12.84% for BWM, respectively, for low, medium, and high zones. The FAHP and BWM models outperformed the AHP model, according to the results of the qualitative validation. The concerned authorities might identify vulnerable locations and plan sustainable groundwater management with the use of these MCDA approaches combined with GIS.

Ground subsidence in major Philippine metropolitan cities from 2014 to 2020

Land subsidence is recognized as one of the hazards that threaten Metro Manila, Philippines, and other major urban areas worldwide. It has become a significant global issue caused by excessive groundwater extraction, rapid urbanization, and natural sediment compaction, exacerbated by climate change through rising sea levels. This paper presents vertical ground motion rates in Philippine metropolitan cities using Sentinel-1 InSAR time series analysis from 2014 to 2020 through UK COMET’s LiCSAR products and the LiCSBAS package of Morishita et al. (2020). The results revealed a maximum subsidence rate of 109 mm/yr in Bulacan Province in Greater Manila. For the first time, this paper also presents ground motion estimates and the following maximum subsidence rates for other Philippine metropolitan cities: 11 mm/yr in Metro Cebu, 38 mm/yr in Metro Davao, 9 mm/yr in Metro Iloilo, and 29 mm/yr in Legazpi City. Areas with remarkably high subsidence rates are observed as circular to elliptical deformation features in vertical motion maps. Sinking areas mostly coincide with industrial and commercial complexes evident as a contiguous distribution of large and expansive man-made structures with distinct radar reflections. Monitoring this hazard is crucial as it increases the risk of floods, building and infrastructure damage, and economic loss, and exposes residents along the coast to worsening tidal incursions and storm surges due to climate change. InSAR is proposed here as a targeted, long-term deformation monitoring tool, especially related to groundwater usage.

REUSE OF TREATED WATER FROM BOJONGSOANG DOMESTIC WASTEWATER TREATMENT INSTALLATION AS WATER FOR INDUSTRIAL PURPOSES

Subdistrict Bojongsoang and its surroundings are based on the 2016-2036 Bandung Regency Spatial Planning, the designated area where the industry is. Currently, there are 125 existing industries operating. The area is also included in groundwater withdrawal through well artesian on a massive scale, including into the national protected area (CAT: Groundwater Basin) Bandung - Soreang Area. Excessive groundwater extraction poses challenges coupled with significant water demand from society and industry. This will result in deteriorated groundwater conditions that require prompt restoration, having already suffered damage. On the other hand, there is Bojongsoang WWTP, which can treat wastewater at 2800 l/s; meanwhile, at the moment, this capacity processing is utilized about 37-40% or about 100m3/day. This research uses a descriptive method. The research results prove that reusing water from Bojongsoang WWTP could produce raw water for the necessity industry of 300 l/s.

Incorporating hydraulic gradient and pumping rate into GALDIT framework to assess groundwater vulnerability to salinity in coastal aquifers: a case study from Urmia Plain, Iran.

The critical role of groundwater in meeting diverse needs, including drinking, industrial, and agricultural, highlights the urgency of effective resource management. Excessive groundwater extraction, especially in coastal regions including Urmia Plain in NW Iran, disrupts the equilibrium between freshwater and saline boundaries within aquifers. Influential parameters governing seawater intrusion-groundwater occurrence (G), aquifer hydraulic conductivity (A), the height of groundwater level above the mean sea level (L), distance from the shore (D), impact of the existing status of seawater intrusion (I), and thickness of the saturated aquifer (T)-merge to shape the GALDIT vulnerability index for coastal aquifers. This study enriches the GALDIT framework by incorporating two additional hydrogeological variables: hydraulic gradient (i) and pumping rate (P). This expansion produces seven distinct vulnerability maps (GALDIT, GAiDIT, GAiDIT-P, GALDIT-i, GALDIT-iP, GALDIT-P, GAPDIT). In the Urmia Plain, the traditional GALDIT index reveals vulnerability values ranging from 2 to 8.1, categorized into six classes from negligible to very high vulnerability. However, the modified indices, GAiDIT and GAiDIT-P, yield a three-class categorization, ranging from low to high vulnerability. The introduction of the "i" and "P" parameters in GALDIT-i and GALDIT-iP enhances the precision of vulnerability mapping, altering class distribution and intensifying vulnerability ratings. The eastern, central, and coastal areas of the Urmia Plain demonstrate high to very high vulnerability levels, in contrast to the lower vulnerability observed in the western regions. Both the GALDIT-P (r = 0.82) and GALDIT-iP (r = 0.81) indices show strong correlations with Cl concentration, thereby improving mapping accuracy over the traditional GALDIT index (r = 0.72). A sensitivity analysis highlights the critical influence of the "i" parameter, suggesting its weighting should be revised. Parameter recalibration serves to amplify the significance of "G," "L," "D," and "i" parameters, while diminishing others. The integration of multiple hydrogeological variables considerably enhances the precision of groundwater vulnerability assessments.

How climate change and groundwater extraction will shape the global terrestrial water cycle pattern

Human groundwater extraction alters hydrological processes, thereby influencing climate through land–atmosphere interactions. As socioeconomic development progresses, the escalating water demand exacerbates conflicts with limited water resources. Nevertheless, potential response of the global terrestrial water cycle to the combined impact of climate change and groundwater extraction under various future scenarios remain vaguely understood. Therefore, this study developed human water regulation projection schemes based on Shared Socio-economic Pathways (SSPs) and Representative Concentration Pathways (RCPs) integrated into a global climate model (CAS-FGOALS-g3). The results show that global water demand in 2100 under the SSP370 scenario almost doubled relative to 2010. The proportion of surface soil drying due to warming is 3%-11% more in the medium- and high-emission scenarios than in the low one. In major irrigated areas, excessive groundwater extraction changed the groundwater storage trend, especially in the Southern Plains of the United States, where the increasing groundwater storage trend became negative compared to scenarios without groundwater extraction. This study underscores the complex interplay between human water use and hydroclimate within an evolving environment, emphasizing the critical need for effective water resource management to mitigate future water stress.

Modelling approach integrating climate projections for coastal groundwater management

Climate change and excessive groundwater extraction are major contributors to rising groundwater salinization due to seawater intrusion in coastal aquifers. This study aims to define a wide-applicable approach in which hydrological balance, boundary conditions, and irrigation water demand, defined over time considering climate change predictions, can integrated into a numerical model of the groundwater system. The approach was tested in a selected coastal aquifer. The approach spans from the past, used to define steady or almost natural conditions for calibration purposes (1950–2000 in the test), to the future (2100), divided in decade steps. The water balance analysis is based on an inverse hydrogeological water balance approach. The future climate change predictions are used to assess variations in boundary conditions of the groundwater model concerning salinity and sea level, recharge, and inflow from upstream aquifers. The approach considers changes in agricultural activities, groundwater demand, and river stage. The regional model is generated using the MODFLOW code for the groundwater flow model and the SEAWAT code for the salt transport model. The test concerns the Metaponto coastal plain, in which a porous aquifer is at salinization risk due to seawater intrusion. In this way, different influences of climate change and human activities are combined to define a 3d view of groundwater depletion and salinization effects. Quantifying these potential effects or risks, adaptation scenarios with numerical assessments are outlined in this study.

Land surface response to groundwater drawdown and recovery in Taiyuan city, Northern China, analyzed with a long-term elevation change measurements from leveling and multi-sensor InSAR

In recent years, a comprehensive program of groundwater management was adopted in Taiyuan city, Northern China, with the aim to prevent the lowering of groundwater level and manage land subsidence due to excessive groundwater pumping in the past decades. Groundwater recovery has been observed in this city following the termination of groundwater pumping. While the link between land subsidence and groundwater pumping is well documented, how the land surface responds to the recovery of groundwater has not been studied in detail. In this study, we analyzed the leveling data from 1956 to 2000 to investigate changes in ground elevation in response to groundwater drawdown prior to the termination of groundwater pumping and combined them with InSAR (Interferometric Synthetic Aperture Radar) displacement data during 2003–2020 to evaluate the effect of groundwater recharge after the termination of groundwater pumping. A method was proposed to merge InSAR time series of displacement derived from multiple satellites (ENVISAT, COSMO-SkyMed, TerraSAR-X, and Sentinel-1) to achieve a consistent, long-term continuous deformation. We found that previous groundwater depression cones in Taiyuan (Xizhang, Wanbailin, Wujiabao, and Xiayuan) have turned into groundwater recovery and the corresponding subsidence centers have switched to land uplift. The subsidence center of Xizhang, north of Taiyuan city, experienced a total subsidence of 749 mm by Aug 2003; it then turned into uplift with an amount of rebound of 9.2 % of previous subsidence by the end of 2020. In central area of Taiyuan, the cumulated subsidence is 1127 mm in Wanbailin, 1817 mm in Xiayuan, and 3343 mm in Wujiabao. Beginning in Aug 2010, they all turned into land uplift, with a rebound of 7.9 %, 4.8 % and 3.6 % of the previous subsidence in each center, respectively. An analysis of the correlation between groundwater level and ground displacement suggests that the ground uplift is related to the poro-elastic rebound mechanism in the porous aquifer system, which is caused by the rise in pore pressure with groundwater recovery, and the amount of subsidence/uplift is controlled by the stratigraphic properties. The adverse impacts on the built environment due to the rising groundwater level were discussed. The findings improve our understanding of anthropogenic ground deformation in complex urban aquifers influenced by groundwater pumping and recharge and provides essential information that can contribute to future groundwater management and groundwater-related hazard mitigation over the Taiyuan city.

Understanding Climate Change and Anthropogenic Impacts on the Salinization of Low‐Lying Coastal Groundwater Systems

AbstractFresh coastal groundwater is a valuable water resource of global significance, but its quality is threatened by saltwater intrusion. Excessive groundwater abstraction, sea‐level rise (SLR), land subsidence and other climate‐related factors are expected to accelerate this process in the future. The objective of this study is to (a) quantify the impact of projected climate change and (b) explore the role of individual hydrogeological boundaries on groundwater salinization of low‐lying coastal groundwater systems until 2100 CE. We employ numerical density‐dependent groundwater flow and salt transport modeling for this purpose, using Northwestern Germany as a case. Separate model variants are constructed and forced with climate data, that is, projected SLR and groundwater recharge, as well as likely ranges of other hydrogeological boundaries, including land subsidence, abstraction rates and drain levels. We find that autonomous salinization in the marsh areas, resulting from non‐equilibrium of the present‐day groundwater salinity distribution with current boundary conditions, is responsible for >50% of the salinization increase until 2100 CE. Sea‐level rise, land subsidence and drain levels are the other major factors controlling salinization. We further show that salinization of the water resources is a potential threat to coastal water users, including water suppliers and the agrarian sector, as well as coastal ecosystems. Regional‐scale uplifting of drain levels is identified as an efficient measure to mitigate salinization of deep and shallow groundwater in the future. The presented modeling approach highlights the consequences of climate change and anthropogenic impacts for coastal salinization, supporting the timely development of mitigation strategies.

The influence of withdrawal-recharging pattern on the deformation characteristics of sand in confined aquifer

Land subsidence caused by excessive groundwater withdrawal has become a global hazard, which demands further researches and the potential measures to control. Using the FlowTrac Ⅱ consolidation test system, six compression tests were designed to investigate the stress state and stress paths of sand within confined aquifers under conditions of withdrawal and recharging. The deformation characteristics of aquifer sand were studied under different withdrawal-recharging patterns. During pumping and recharge processes, sand deformation responses were observed to lag behind changes in applied stress. The characteristics of this hysteresis effect on deformation were summarized. The alternating phenomenon of rebound and compression of sand deformation under the recharging process is analyzed. When the recharging effect was relatively small than withdrawing effect under the stable withdrawal-recharging pattern, the compression deformation was observed in the recharging process. The research results provide a rational explanation for the continuous compression deformation of the aquifer during groundwater level recovery and offer experimental evidence for the rational design of artificial groundwater recharge in engineering construction.

Microtremor Analysis to Identify Fissure Vulnerable Zones in Demak, Central Java, Indonesia

Demak Regency, located in Central Java, Indonesia stands out among the regencies for its rapid development and regional growth, leading to a significant reliance on groundwater. This is thought to be caused by low precipitation and the geological characteristics of Demak Regency, which is mostly located on alluvial plains. To address these concerns, this study aimed to pinpoint regions vulnerable to ground fractures resulting from excessive groundwater extraction compounded by seismic activity. The research encompassed 191 locations, including 177 single station microtremor measurement points and 14 array microtremor measurement points. Single station microtremor measurements utilized the Horizontal to Vertical Spectral Ratio (HVSR) method, while array measurements employed the Spatial Autocorrelation (SPAC) method. Ground shear strain values spanning from 32.12 × 10-6 - 96.39 × 10-6. Notably, areas exhibiting heightened values are concentrated in Wonosalam Subdistrict and the Southwest of Karangtengah Subdistrict. The morphology of the bedrock within the study area tends to mirror the sedimentary layer's thickness, reflecting relatively minimal surface height discrepancies at the measurement points. Vulnerability to fissures resulting from excessive groundwater extraction and seismic activity is concentrated on the north side of Wonosalam District, the eastern sector of Demak District, and a small section of Mijen District.

Mapping and assessment of groundwater pollution risks in the main aquifer of the Mostaganem plateau (Northwest Algeria): utilizing the novel vulnerability index and decision tree model.

Water plays a pivotal role in socio-economic development in Algeria. However, the overexploitations of groundwater resources, water scarcity, and the proliferation of pollution sources (including industrial and urban effluents, untreated landfills, and chemical fertilizers, etc.) have resulted in substantial groundwater contamination. Preserving water irrigation quality has thus become a primary priority, capturing the attention of both scientists and local authorities. The current study introduces an innovative method to mapping contamination risks, integrating vulnerability assessments, land use patterns (as a sources of pollution), and groundwater overexploitation (represented by the waterhole density) through the implementation of a decision tree model. The resulting risk map illustrates the probability of contamination occurrence in the substantial aquifer on the plateau of Mostaganem. An agricultural region characterized by the intensive nutrients and pesticides use, the significant presence of septic tanks, widespread illegal dumping, and a technical landfill not compliant with environmental standards. The critical situation in the region is exacerbated by excessive groundwater pumping surpassing the aquifer's natural replenishment capacity (with 115 boreholes and 6345 operational wells), especially in a semi-arid climate featuring limited water resources and frequent drought. Vulnerability was evaluated using the DRFTID method, a derivative of the DRASTIC model, considering parameters such as depth to groundwater, recharge, fracture density, slope, nature of the unsaturated zone, and the drainage density. All these parameters are combined with analyses of inter-parameter relationship effects. The results show a spatial distribution into three risk levels (low, medium, and high), with 31.5% designated as high risk, and 56% as medium risk. The validation of this mapping relies on the assessment of physicochemical analyses in samples collected between 2010 and 2020. The results indicate elevated groundwater contamination levels in samples. Chloride exceeded acceptable levels by 100%, nitrate by 71%, calcium by 50%, and sodium by 42%. These elevated concentrations impact electrical conductivity, resulting in highly mineralized water attributed to anthropogenic agricultural pollution and septic tank discharges. High-risk zones align with areas exhibiting elevated nitrate and chloride concentrations. This model, deemed satisfactory, significantly enhances the sustainable management of water resources and irrigated land across various areas. In the long term, it would be beneficial to refine "vulnerability and risk" models by integrating detailed data on land use, groundwater exploitation, and hydrogeological and hydrochemical characteristics. This approach could improve vulnerability accuracy and pollution risk maps, particularly through detailed local data availability. It is also crucial that public authorities support these initiatives by adapting them to local geographical and climatic specificities on a regional and national scale. Finally, these studies have the potential to foster sustainable development at different geographical levels.

Systematic and highly resolved modelling of biodiversity in inherently rare groundwater amphipods

AbstractAimGroundwater ecosystems harbour a unique biodiversity, but remain poorly studied, mainly due to difficulties in accessibility and imperfect species detection. Consequently, knowledge on the state and change of groundwater biodiversity remains highly deficient. In the context of global warming and excessive groundwater extraction, understanding groundwater from an ecosystem‐perspective, including organism diversity and distribution, is essential. This study presents the largest ever systematic assessment of groundwater amphipods, which are a key component of European groundwater biodiversity.LocationSwitzerland (41,285 km2), including data from 906 sampling sites.TaxonGroundwater amphipods, genera Niphargus and Crangonyx (Crustacea, Amphipoda).MethodsWe applied a highly standardized citizen science approach to collect repeated groundwater fauna samples in collaboration with municipal drinking water providers. Using detection–nondetection data of the genetically identified groundwater amphipod species, we assessed the overall species diversity of both rare and common species. The distribution of commonly found species was predicted using multispecies occupancy modelling.ResultsWe retrieved 3882 samples from 906 sites, yielding 2350 groundwater amphipod individuals. We identified a remarkable species diversity, comprising few commonly and many rarely found species. Considering commonly found species, we identified distinct distribution ranges, low local species richness and a predominance of negative co‐occurrences. In contrast, a major portion of species were found rarely (generally at just one or two sites each), distributed uniformly throughout the study area and unrelated to common species' recognized hotspots. Many of these rarely found species are not yet formally described.Main ConclusionsOur results give robust emphasis on the rare occurrence and narrow distribution of many groundwater dwellers. Our systematic and standardized sampling data of groundwater amphipods suggest that rarity is particularly prominent and inherent to groundwater organisms. We emphasize the need of systematic data to integrate rare groundwater species in biodiversity assessments, especially in times of global change.

Hydrological response of the largest inland tectonic basin in Japan

The Itoigawa-Shizuoka tectonic line formed the largest inland tectonic basin in Japan. Taking advantage of the characteristics of the large tectonic basin, this study aims to clarify the hydrological response related to groundwater recharge and discharge in this area from field measurements such as monthly spring discharge measurements in the spring belt, infiltration measurements of irrigation recharge in rice paddy fields and analysis of stable isotopic ratios of oxygen and hydrogen. Volumetric water flow measurements in the tectonic basin demonstrate that the hydrological response function (HRF) is expressed as a linear equation. Despite the complex topography and geology of the mountain catchment and artificial recharge within the basin, this HRF is maintained, except for forced artificial irrigation in August when the natural water supply is significantly reduced, and except in March and April when snowmelt flows into the river. This study clarifies that monthly fluctuations in total groundwater flow within a basin can be estimated by applying HRF to monitoring data of total surface flow at the farthest downstream. The field measurements demonstrate that the rainfall in the mountain catchment area and artificial irrigation recharge in the basin greatly influence the fluctuation of groundwater flow rate, especially on the fluctuation of the spring water in the spring belt. Field data inferred that the frequent depletion of the springs in the inland tectonic basin, where all groundwater emerges at the most downstream, depends on the rapid decline in annual rainfall in mountain catchment areas. These observations suggest that the total groundwater resource in this region was affected not only by reduced irrigation recharge due to the historical paddy acreage reduction program implemented in Japan from 1971 to 2018, and by excessive groundwater extraction, but also by rapid decline in annual rainfall in mountain catchments that occurs non-periodically.

Research Advances of Groundwater Nitrate Pollution and Source Apportionment in China

Groundwater nitrate (NO3-) contamination in China has become a serious environmental problem, especially in agricultural production areas, which greatly affects the safety of drinking groundwater and requires urgent attention. In this study, the main sources of groundwater nitrate in China were reviewed, including atmospheric deposition, soil nitrogen, agricultural fertilization, and fecal sewage, among which fecal sewage and agricultural fertilization were the main reasons for the excessive groundwater nitrate. The application of hydrochemical analysis, multivariate statistical analysis, stable isotope tracer method, and microbial source tracking in the source apportionment of groundwater nitrate was summarized. All types of source apportionment methods had certain limitations. It is suggested that a variety of methods should be used to identify the source of groundwater nitrate, and the contribution rate of different pollution sources should be calculated using multivariate statistical analysis and isotope quantitative analysis models. The source apportionment of nitrate pollution has undergone a process from qualitative to quantitative research. At present, the SIAR and MixSIAR models based on δ15N-NO3-and δ18O-NO3- have been used widely to analyze the source of nitrate. However, due to the overlap of isotope characteristic values of different input end-members, the difference in δ15N-NO3-and δ18O-NO3- values under different spatial and temporal changes, and the influence of isotope fractionation in the process of nitrogen migration and transformation, the results calculated by the model remain uncertain. It is necessary to further optimize the analytical method of the model to obtain the source of nitrate pollution and its contribution rate more accurately to further aid in the scientific management of groundwater resources.

Spatio-temporal variation of depth to groundwater level and its driving factors in arid and semi-arid regions of India

Climate change and increasing anthropogenic activities, such as over-exploitation of groundwater, are exerting unavoidable stress on groundwater resources. This study investigated the spatio-temporal variation of depth to groundwater level (DGWL) and the impacts of climatic (precipitation, maximum temperature, and minimum temperature) and anthropogenic (gross district product (GDP), population, and net irrigated area (NIA)) variables on DGWL during 1994–2020. The study considered DGWL in 113 observation wells and piezometers located in arid western plains (Barmer and Jodhpur districts) and semi-arid eastern plains (Jaipur, Ajmer, Dausa, and Tonk districts) of Rajasthan State, India. Statistical methods were employed to examine the annual and seasonal patterns of DGWL, and the generalized additive model (GAM) was used to determine the impacts of climatic and anthropogenic variables on DGWL. During 1994–2020, except for Barmer District, where the mean annual DGWL was almost constant (around 26.50 m), all other districts exhibited increase in DGWL, with Ajmer District experiencing the most increase. The results also revealed that 36 observation wells and piezometers showed a statistically significant annual increasing trend in DGWL and 34 observation wells and piezometers exhibited a statistically significant decreasing trend in DGWL. Similarly, 32 observation wells and piezometers showed an statistically significant increasing trend and 37 observation wells and piezometers showed a statistically significant decreasing trend in winter; 33 observation wells and piezometers indicated a statistically significant increasing trend and 34 had a statistically significant decreasing trend in post-monsoon; 35 observation wells and piezometers exhibited a statistically significant increasing trend and 32 observation wells and piezometers showed a statistically significant decreasing trend in pre-monsoon; and 36 observation wells and piezometers reflected a statistically significant increasing trend and 30 observation wells and piezometers reflected a statistically significant decreasing trend in monsoon. Interestingly, most of the observation wells and piezometers with increasing trends of DGWL were located in Dausa and Jaipur districts. Furthermore, the GAM analysis revealed that climatic variables, such as precipitation, significantly affected DGWL in Barmer District, and DGWL in all other districts was influenced by anthropogenic variables, including GDP, NIA, and population. As a result, stringent regulations should be implemented to curb excessive groundwater extraction, manage agricultural water demand, initiate proactive aquifer recharge programs, and strengthen sustainable management in these water-scarce regions.

Alternate wetting and drying irrigation: A strategic approach to increase water productivity and managing of sheath blight disease in rice

The traditional practice of continuous flooding irrigation in rice cultivation has resulted in excessive groundwater exploitation and low water productivity of crop. This study aimed to evaluate the impact of two irrigation techniques, alternate wetting and drying (AWD) and continuous flooding (CF) on the development of sheath blight disease (Rhizoctonia solani Kuhn) and water productivity of poplar rice cultivar PR 121 during the kharif seasons 2021 and 2022. Irrigating the rice fields two days after percolation of ponded water as follow AWD technique was identified the optimal irrigation practice for saving irrigation water and managing of sheath blight disease in rice crop. The AWD technique of irrigation was significantly reduced the disease severity (32.3%), number of irrigations (21.3%) and volume of irrigation water (20.3%), while increasing water productivity (29.9%) and grain yield (1.26%) as compared to the traditional continuous flooding system in rice cultivation.. KEYWORDS :Irrigation, severity, sheath blight, water productivity, yield