Seawater Intrusion Research Articles

Impacts of Sea‐Level Rise on Coastal Groundwater Table Simulated by an Earth System Model With a Land‐Ocean Coupling Scheme

AbstractSea‐level rise (SLR) poses a severe threat to the coastal environment through seawater intrusion into freshwater aquifers. The rising groundwater table also exacerbates the risk of pluvial, fluvial, and groundwater flooding in coastal regions. However, current Earth system models (ESMs) commonly ignore the exchanges of water at the land‐ocean interface. To address this gap, we developed a novel land‐ocean hydrologic coupling scheme in a state‐of‐the‐science ESM, the Energy Exascale Earth System Model version 2 (E3SMv2). The new scheme includes the lateral exchange between seawater and groundwater and the vertical infiltration of seawater driven by the SLR‐induced inundation. Simulations were performed with the updated E3SMv2 for the global land‐ocean interface to assess the impacts of SLR on coastal groundwater under a high CO2 emission scenario. By the middle of this century, seawater infiltration on the inundated areas will be the dominant component in the land‐ocean coupling process, while the lateral subsurface flow exchange will be much smaller. The SLR‐induced seawater infiltration will raise the groundwater levels, enhance evapotranspiration, and increase runoff with distinct spatial patterns globally in the future. Although the coupling process is induced by SLR, we found topography and warming temperature have more control on the coupling impacts, probably due to the relatively modest magnitude of SLR during the selected future period. Overall, our study suggests significant groundwater and seawater exchange at the land‐ocean interface, which needs to be considered in ESMs.

The Impact of Saline Water on Women's Health in the Coastal Region of Bangladesh: Special Attention on Menstrual Hygiene Practices.

Introduction Salinity intrusion is the most common global concern along coastlines, but it can happen inland also. The lack of freshwater is the primary issue affecting the coastal areas. Many health problems are prevalent among the inhabitantsdue to their frequent use of salted water. The health of women living along the coastline is getting progressively compromised due to salinity intrusion. Objectives The study aims to determine menstrual health practices and other health problems faced bywomen in the coastal region of Bangladesh. Methods The study was conducted using a survey research designfrom May 2023 to October 2023 on rural women aged 18 to 45 years, who lived in the Bangladeshi village of Koyra Upazila in the Khulna district. Thesample size of the study was 101. Open- and closed-ended questions from a planned interview schedule were used to gather primary data. Additional information from appropriate sources, e.g., newspapers, publications, and books, was utilized to enhancethe comprehensiveness of statistical analysis and support rationality. A p-value of 0.05 was considered significant. Statistical analysis was performed using STATA version 15 (StataCorp LLC, College Station, TX). Results Menstrual hygiene practices showed a higher prevalence of using fabric rags and reusing them after rinsing them in salt water (72.3%) than sanitary pads (25.7%). It was observed that the risk of diarrhea among tubewell water and rainwaterusers was significantly lowered by 0.25 times (95% CI = 0.06, 0.99; p = 0.049) and 0.06 times (95% CI = 0.01, 0.43; p = 0.005), respectively, compared to pond water users. Conclusion Salinityhas a significant impact on the livelihoods and health of coastal women. The village womenare unaware of the health risks of excessive saline water use. Establishing an adequate supply of freshwater reservoirsfor the entire communitythroughout the yearis analternativefor womento use as a source of water for hygiene necessities.

Sand dunes Groundwater Quality in the context of Climate Change: A Case Study of Phao Dai Hamlet, Tien Giang, Vietnam

Abstract Climate change is currently the main cause for deteriorating freshwater sources worldwide. It has raised sea levels and fluctuated rainfall over the years, causing salinity intrusion among coastal areas. Therefore, sand dunes, one of the primary freshwater sources formed by depositing alluvium at higher sea level altitudes, have been affected by climate change. This study focused on the impact of climate conditions on the freshwater supply in these potential areas. Fifteen groundwater samples from 06 dug wells in Phao Dao hamlet, Tien Giang province, Vietnam, were collected monthly from August 2016 to March 2017 to be analyzed at the Institute of Coastal and Offshore Engineering (ICOE). The results showed that most of the nutrient-related analyzed parameters were within the thresholds of QCVN 09 – MT: 2015/BTNMT for groundwater use and QCVN 01:2009/ BYT for drinking water quality, but not salinity-related parameters. In addition, salinity, CaCO3, and TDS unpredictably fluctuated depending on the seasons and lowered from the coastal to inland areas.

Modeling Saltwater Intrusion into Groundwater Using a Prey–Predator Model

Modeling Saltwater Intrusion into Groundwater Using a Prey–Predator Model

Effects of groundwater pumping on pore water flow and salt transport in tide‐controlled unconfined coastal aquifers

AbstractUnconfined coastal aquifers are a main pathway for land‐sourced solutes to enter the oceans. The migration of these solutes in aquifers is highly affected by the groundwater flow and salt transport processes, which are, to a great extent, controlled by tides. While many studies have examined how tidal oscillations would influence the subsurface hydrodynamics in coastal aquifers, most of them ignored the potential impact of groundwater pumping, a common practice in coastal areas to satisfy the demand for freshwater. This study, by means of laboratory experiments and numerical simulations, explored the combined effects of tides and groundwater pumping on the pore water flow and salinity distributions in an unconfined coastal aquifer. The results show that, in a tide‐controlled aquifer, the addition of groundwater pumping would exacerbate the degree of seawater intrusion and lead to wider spreading and deeper penetration of the upper saline plume. Moreover, groundwater pumping would enhance the tide‐driven circulation in the upper saline plume and weaken the density‐driven circulation in the saltwater wedge, ultimately leading to the reduction in total submarine groundwater discharge. These findings may promote a deep insight into the complex coastal groundwater systems experiencing human activities, and provide guidance for better evaluating the environmental impact of groundwater pumping.

Assessment of groundwater vulnerability and risk to pollution in Con Dao island, Ba Ria - Vung Tau, Vietnam

Abstract The assessment of groundwater vulnerability has been widely used to manage and prevent groundwater from contamination risk. This study applied the model of GIS-based GALDIT was for groundwater vulnerability and risk assessment in a coastal district of Con Dao island, Ba Ria-Vung Tau, Vietnam. The Groundwater Risk Assessment Model (GRAM) was used to assess the risk of groundwater pollution in the study region. The GALDIT model used six hydrogeological components to generate a GALDIT Index map, which illustrates how vulnerable the local groundwater is to contamination. The platform of GIS-based GRAM was exploited to construct risk maps related to salinity intrusion, hazard release, and hazard consequences. According to the findings, more than 80% of the groundwater in Con Dao district is vulnerable to saltwater intrusion, with the greatest concentration in the district’s central section. Only 18.12% of the district, in the Co Ong region to the northeast of the Con Dao district, has low or very low susceptibility. However, after accounting for contamination barriers and the capacity to identify and detect risks, it was shown that most areas, or around 87% of the study area, had transitioned to a low-risk level of groundwater pollution. The groundwater vulnerability and risk maps created serve as baseline information for decision-makers in governance and planning to effectively monitor and protect groundwater resources from pollution.

Lateral Transport Controls the Tidally Averaged Gravitationally Driven Estuarine Circulation: Tidal Mixing Effects

Abstract In classic models of the tidally averaged gravitationally driven estuarine circulation, denser salty oceanic water moves up the estuary near the bottom, while less dense riverine water flows toward the ocean near the surface. Traditionally, it is assumed that the associated pressure gradient forces and salt advection are balanced by vertical mixing. This study, however, demonstrates that lateral (across the estuary width) transport processes are essential for maintaining the estuarine circulation. This is because for realistic estuarine bathymetry, the depth-integrated salt transport up the estuary is enhanced in the deeper estuary channel. A closed salt budget then requires the lateral transport of this excess salt in the deeper channel toward the estuarine flanks. To understand how such lateral transport affects the estuarine salt and momentum balances, we devise an idealized model with explicit lateral transport focusing on tidally averaged lateral mixing effects. Solutions for the along-estuary velocity and salinity are nondimensionalized to depend only on one single nondimensional parameter, referred to as the Fischer number, which describes the relative importance of lateral to vertical tidal mixing. For relatively strong lateral tidal mixing (greater Fischer number), salinity and velocity variations are predominantly vertical. For relatively weak lateral tidal mixing (smaller Fischer number), salinity and velocity variations are predominantly lateral. Overall, lateral transport greatly affects the estuarine circulation and controls the estuarine salinity intrusion length, which is demonstrated to scale inversely with the Fischer number.

Hydrogeochemical features, genesis, and quality appraisal of confined groundwater in a typical large sedimentary plain.

The confined groundwater of arid sedimentary plains has been disturbed by long-term anthropogenic extraction, and its hydrochemical quality is required for sustainable development. The present research investigates the hydrochemical characteristics, formation, potential health threats, and quality suitability of the confined groundwater in the central North China Plain. Results show that the confined groundwater has a slightly alkaline nature in the study area, predominantly dominated by fresh-soft Cl-Na and HCO3-Na types. Water chemistry is governed by water-rock interactions, including dissolution of evaporites and cation exchange. Approximately 97% of the sampled confined groundwaters exceed the prescribed standard for F-. It is mainly due to geological factors such as mineral dissolution, cation exchange, and competitive adsorption of HCO3 - and may also be released from compacted soils because of groundwater extraction. Enriched F- in the confined groundwater can pose an intermediate and higher non-carcinogenic risk to more than 90% of the population. It poses the greatest health threat to the population in the north-eastern part of the study area, especially to infants and children. For sustainable development, the long-term use of confined groundwater for irrigation in the area should be avoided, and attention should also be paid to the potential soil salinization and infiltration risks. In the study area, 97% of the confined groundwaters are found to be excellent or good quality for domestic purposes based on Entropy-weighted Water Quality Index. However, the non-carcinogenic health risk caused by high contents of F- cannot be ignored. Therefore, it is recommended that differential water supplies should be implemented according to the spatial heterogeneity of confined groundwater quality to ensure the scientific and rational use of groundwater resources. PRACTITIONER POINTS: The hydrochemistry quality of confined groundwater in an arid sedimentary plain disturbed by long-term anthropogenic extraction was investigated. The suitability of confined groundwater for multiple purposes such as irrigation and drinking were evaluated. The hydrochemical characteristics and formation mechanism of confined groundwater under the influence of multiple factors were revealed.

A quantitative analysis framework for analyzing impacts of climate change on water-food-energy-ecosystem nexus in irrigation areas based on WEAP-MODFLOW

Agricultural irrigation areas are vital for ensuring food security under climate change conditions with extensive water and energy consumption, which will inevitably exert pressures on ecosystem especially in arid and semi-arid areas normally with higher ecosystem degradation risk. The key to realize sustainable development lies in a quantitative analysis framework for analyzing impacts of climate change on water-food-energy-ecosystem nexus. Climate change exacerbates these challenges by impacting food production, water resources utilization, energy consumption for water supply and ecological conditions in irrigation areas. In this work, a quantitative analysis framework to analyze the trade-offs and synergies among various scenarios within the water-food-energy-ecosystem nexus in irrigation area was proposed. Two climate models (BCC and MIR1) were selected from the Coupled Model Intercomparison Project Phase 6 (CMIP6), and three Shared Socioeconomic Pathway (SSP) scenarios (SSP245, SSP370, and SSP585) were employed to quantitatively evaluate different sustainable development strategies among water, food, energy and ecosystem sectors from five key aspects: irrigation demand, food production, groundwater supply for irrigation, ecological base flow and irrigation water shortage. The results show that the sustainability index (SI) of combined management scenarios CC1-IM, CC5-IM, CC1-WSI and CC5-WSI could be 12% to 25% higher than that of the corresponding single management scenario. Among the four climate change and management scenarios, the SI of the integrated measures scenario (CC1-IM, CC5-IM) was the highest, with values of 1.39 and 1.12 respectively. This work highlights the pomising results of the integrated measures scenario in alleviating food production challenges, protecting ecological base flows, reducing groundwater extraction, alleviating irrigation water shortages and improving water supply efficiency when dealing with climate change challenges.

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.

Groundwater Potential of the Jakarta Groundwater Basin using the Darcy Equation Method

The annual increase in population leads to a growing demand for water. To control groundwater utilization in a directed manner is to extract groundwater according to groundwater potential. The research aims to analyze the groundwater potential in the Jakarta Groundwater Basin in terms of quantity and quality. The method used is primary data analysis by determining quantity potential using the Darcy equation method with additional calculations of groundwater volume and quality potential based on drinking water quality standards from the Republic of Indonesia Minister of Health Regulation no. 2 of 2023 and WHO of 2022. The dynamic potential for unconfined aquifers ranges from 2,663–1,372,901 m³/year, while for confined aquifers range from 184,991–1,895,288 m³/year. The static potential for unconfined aquifers ranges from 266,852–3,252,654 m³, while for confined aquifers ranges from 1,317,862–30,620,266 m³. Based on groundwater quality standards for drinking water from the Minister of Health and WHO for the parameters pH, TDS, Na⁺, Cl⁻, SO₄²⁻ and NO₃⁻, there are 15 samples from 53 samples of unconfined aquifer and 36 samples from 75 samples of confined aquifer that meet standards.

Comparative Analysis with Statistical and Machine Learning for Modeling Overall and High Salinity along the Scheldt Estuary

Saltwater intrusion is an essential problem in estuaries that can threaten the ecological environment, especially in high-salinity situations. Therefore in this paper, traditional multiple linear regression (MLR) and artificial neural network (ANN) modeling are applied to forecast overall and high salinity in the Lower Scheldt Estuary, Belgium. Mutual information (MI) and conditional mutual information (CMI) are used to select optimal driving forces (DFs), with the daily discharge (Q), daily water temperature (WT), and daily sea level (SL) selected as the main DFs. Next, we analyze whether applying a discrete wavelet transform (DWT) to remove the noise from the original time series improves the results. Here, the DWT is applied in Signal-hybrid (SH) and Within-hybrid (WH) frameworks. Both the MLR and ANN models demonstrate satisfactory performance in daily overall salinity simulation over the Scheldt Estuary. The relatively complex ANN models outperform MLR because of their capabilities of capturing complex interactions. Because the nonlinear relationship between salinity and DFs is variable at different locations, the performance of the MLR models in the midstream region is far inferior to that in the downstream region during spring and winter. The results reveal that the application of DWT enhances simulation of both overall and high salinity in this region, especially for the ANN model with the WH framework. With the effect of Q decline or SL rise, the salinity in the middle Scheldt Estuary increases more significantly, and the ANN models are more sensitive to these perturbations.

Assessing vulnerabilities and resilience in the Indian Sundarbans: A case study of gosaba C.D block, West Bengal, India

The Sundarbans region, being a largest mangrove extending over 10,000 sq. Km, is one of the most critical ecosystems in the world. Due to its coastal location, the region has been severely affected by climatic events, including recent cyclones Amphan and Yaas. The present study examines the nature of vulnerabilities and subsequent adaptation and recovery processes of the affected villages in the Gosaba C.D block due to the impacts of back-to-back extreme cyclonic events. In this study, we first introduce the sample characteristics with the help of descriptive statistics, followed by Principal Component Analysis (PCA) to assess the vulnerabilities faced by the coastal communities due to super-cyclones. A binary logistic regression was computed to predict the schemes accessed by the coastal communities based on criteria and predicted variables. Results indicate that agricultural land is most affected by saline intrusion, inundation, and erosion; while homesteads are affected by cyclones, inundation and erosion. This study also reveals the strong disparities among villagers’ in accessing the schemes provided by different institutions. Therefore, the socio-economic conditions of the coastal communities have deteriorated and altered their occupations from farming to fishing and other economic activities, with many migrating in search of employment. In conclusion, the adaptation strategies and recovery processes toward resilience building of the communities have been measured through frequency distribution based on selected variables. There is a need for building resilience in order to live with uncertainties, as their changing occupations have already indicated. Moving to other locations with proper planning and policy formulation by the state government may help them face the multiple challenges along with providing multiple options for livelihood security.

Assessing terrestrial water storage variations in Afghanistan using GRACE and FLDAS-Central Asia data

Study regionAfghanistan, Central Asia. Study focusIn this study, we evaluated the terrestrial water storage dynamics in Afghanistan and its five major river basins using the terrestrial water storage anomalies (TWSA) from three Gravity Recovery and Climate Experiment (GRACE) mascons observations from JPL, CSR, and GSFC processing centers, and the Famine Early Warning Systems Network (FEWS NET) Land Data Assimilation System – Central Asia (FLDAS-CA) simulation. New hydrological insights for the regionsSince 2008, due to intense and prolonged drought conditions and groundwater overexploitation, TWS in Afghanistan has been decreasing at an alarming rate. The average slopes of the TWSA trend in Afghanistan for the GRACE period (2003–2016) of the three products range between − 3.6 to − 4.8 mm/year. The decrease in TWS is further exacerbated during the GRACE-FO period (2019–2022), ranging between − 20.4 to − 30 mm/year. Because groundwater is heavily relied on in the country but human-induced change (i.e., groundwater extraction) is not simulated in FLDAS-CA, a significant difference could be observed between GRACE observations and FLDAS-CA results, especially following after each severe drought event (e.g., 2008, 2018) when substantial groundwater extraction occurred. The assimilation of GRACE observations into the FLDAS-CA framework will undoubtedly have a positive impact for decision-makers and local stakeholders in preparing and mitigating the impacts of drought and groundwater overexploitation in Afghanistan and Central Asia.

Extent of gross underestimation of precipitation in India

Abstract. The underestimation of precipitation (UoP) in the hilly and mountainous parts of South Asia is estimated by some studies to be as large as the observed precipitation (P). However, UoP has been analyzed to only a limited extent across India. To help bridge this gap, watershed-scale UoP was analyzed using various P datasets within a water imbalance analysis. Among these P datasets, the often-used Indian Meteorological Department (IMD) dataset is of primary interest. The gross UoP was identified by analyzing the extent of the imbalance in the annual water budget of watersheds corresponding to 242 river gauging stations for which quality-controlled data on catchment boundaries and streamflow are available. The water year (WY)-based volume of observed annual P was compared against the observed annual streamflow (R) and the satellite-based actual evapotranspiration (ET). Across many watersheds of both Northern and Peninsular India, spurious water imbalance scenarios (P≤R or P≪R+ET) were realized. It is shown that the management of water, such as groundwater extraction, reservoir storage and water diversion, is generally minimal compared to the annual P in such watersheds. It is also shown that annual changes in terrestrial water storage are minimal compared to the annual P in such watersheds. Assuming that data on R (and, to a lesser extent, ET) are reliable, it is concluded that UoP is very likely the cause of this imbalance. Inter-watershed groundwater flow (IGF) is assumed to be negligible. While the effect of IGF on R is unknown, examples are provided which show that IGF is unlikely to be the cause of the observed imbalance in certain watersheds. All 12 of the P datasets analyzed here suffer from UoP, but the extent of the UoP varies by dataset and region. The reanalysis-based datasets ERA5-Land and IMDAA are less affected by UoP than the IMD dataset. Based on the 30-year period of WY 1985–2014, P for the whole of India could be as much as 19 % (ERA5-Land) to 37 % (IMDAA) higher than that from the IMD, with substantial variability within years and river basins. The actual magnitude of UoP is speculated to be even greater. Moreover, trends seen in the IMD's P are not always present in ERA5-Land and IMDAA. Studies using IMD should exercise caution since UoP could lead to the misrepresentation of water budgets and long-term trends. Limitations of this study are discussed.

Epidemiological association between water salinity and blood pressure in coastal populations: ambient temperature’s role as a confounder

Due to global climate change and anthropogenic activities, many low-lying coastal communities experience high sodium in drinking water as a result of saltwater intrusion, an emerging environmental health problem in many coastal regions. Drinking saline water is associated with higher sodium intake and hypertension. Exposure to higher ambient temperatures is common in many regions affected by saltwater intrusion, particularly in tropical and subtropical regions. Little attention has been given to the role of ambient temperature in the epidemiological association between drinking saline water and population blood pressure. We argue that high ambient temperatures increase water salinity and influence communities' sodium intake, urinary sodium excretion, and blood pressure. Hence, we hypothesize that ambient temperature is a potential confounder for the relationship between drinking saline water and population blood pressure. Testing the hypothesis requires a detailed measurement of urinary, blood, and sweat biomarkers (e.g., sodium), the population's blood pressure, and their drinking water’s salinity. An increasing number of coastal regions and islands will face the dual burden of high ambient heat exposure and saltwater intrusion in the future. Future studies are needed to determine the association between drinking saline water and blood pressure after adjusting for ambient temperature in saltwater intrusion-affected regions.

Quantifying groundwater depletion in Arabian Peninsula transboundary aquifer systems: Understanding natural and anthropogenic drivers

Groundwater is the primary source of freshwater for domestic, agricultural, and industrial usage in the Arabian Peninsula countries. It is increasingly becoming a limited resource due to human activities leading to excessive depletion and contamination. Thus, sustainable management of groundwater resources in this region is critical. The groundwater in the Arabian Peninsula countries is primarily found in transboundary systems such as the Wajid, Umm Er Radhuma, and Wasia Aquifers shared between Saudi Arabia, Iraq, Syria, Yemen, and Oman. These systems have no groundwater-sharing agreements, which leads to a lack of data sharing, unsustainable and uncoordinated development, rapid water depletion, water quality deterioration, and land subsidence. This study examines the Wajid, Umm Er Radhuma, and Wasia aquifer systems from April 2002 to May 2021 by analyzing monthly gravity field solutions from GRACE and GRACE-FO satellite data, other remote sensing observations, information from the Global Land Data Assimilation System (GLDAS), as well as field data to determine how regional water resources are changing over time and to identify the factors that influence these resources. The sharp decline in Total Water Storage Anomalies (TWSA) and the Groundwater Storage Anomalies (GWSA) across all three systems is caused by a combination of climatic and human factors. The observed decline in Total Water Storage can be partly attributed to a decrease in regional rainfall, whereas the depletion of Groundwater Storage has a strong correlation with the rise in groundwater extraction for irrigation purposes in the 2010s. The recent rise is groundwater depletion in specific areas of central Saudi Arabia may be attributed to agricultural irrigation and rapid urban development. The results are insightful for monitoring water storage in management plans and decision-making processes to preserve and efficiently use groundwater resources.

Predicting seawater intrusion in coastal areas using machine learning: A case study of arid coastal aquifers, Saudi Arabia

Groundwater is a vital resource for communities in arid regions, such as Saudi Arabia, where seawater intrusion poses a significant threat. To determine groundwater quality with traditional methods is time-consuming and costly process. In this study, we developed a machine learning method as a tool for predicting seawater intrusion in coastal areas using groundwater chemical parameters. We analysed 99 water sample data from the Red Sea and 42 from eastern coast of Saudi Arabia for 13 chemical parameters and conducted two experiments with and without chloride parameter. Unlike previous studies that developed complex machine learning methods, we focus on lightweight machine learning algorithms to model seawater intrusion for possibility of sensor deployment in future. The machine learning algorithms assessed and compared are namely decision trees, ensemble machine learning methods (Random Forest and Gradient Boosting), support vector machines, multilayer perceptrons, and ridge regression. With the chloride parameter included, ridge regression emerged as the best model, with an R2 of 99.8% and the lowest Akaike and Bayesian information criteria values. Without chloride data, multilayer perceptron achieved a marginally higher R2 of 98.7% but required longer training times. Notably, a high accuracy was maintained without chloride parameter, demonstrating the capacity of machine learning for augment monitoring. This research underscores the effectiveness of ridge regression and neural networks in predicting seawater intrusion, enabling the accurate mapping of vulnerable areas to inform adaptive management strategies for groundwater preservation. The regional scope of this study offers valuable insights for other arid coastal regions that rely on groundwater and threatened by seawater intrusion.

A meta-ensemble machine learning strategy to assess groundwater holistic vulnerability in coastal aquifers

Assessing the vulnerability of groundwater in coastal aquifers is crucial for mitigating risks associated with seawater intrusion and anthropogenic impacts. This study introduces an innovative machine learning (ML)-enhanced methodology that synergizes the strengths of two established vulnerability assessment frameworks, DRASTIC and GALDIT. The hybrid approach overcomes the limitations of each framework—DRASTIC's inadequacies in coastal settings and GALDIT's limited consideration of agricultural and industrial impacts. Utilizing advanced decision tree-based ML algorithms—Adaptive Boosting (AdaBoost), Extreme Gradient Boosting (XGBoost), Light Gradient Boosting Machine (LGBM), and Random Forest (RF)—this research was conducted in the Azarshahr Plain, NW Iran. Model efficacy was validated using Pearson's correlation coefficient (r) and distance correlation (DC), with nitrate (NO3−) and total dissolved solids (TDS) serving as proxies for evaluating the DRASTIC and GALDIT models, respectively. The original DRASTIC indices exhibited weak correlations with NO3− (r = 0.24, DC = 0.25), but ML-enhanced models, particularly AdaBoost, showed significant improvements (r = 0.78, DC = 0.79). Similar enhancements were observed with GALDIT, where correlations improved markedly with AdaBoost integration. A sophisticated second-level AdaBoost meta-ensemble was developed to integrate enhanced DRASTIC and GALDIT assessments, achieving superior correlation metrics (r = 0.80, DC = 0.84 for NO3−; r = 0.82, DC = 0.83 for TDS). These results underscore the effectiveness of an integrated ML-based approach in advancing beyond traditional vulnerability assessment methods, providing a more comprehensive, accurate, and robust evaluation of coastal aquifer vulnerability.

Analysis of drainage morphometry and spectral indices using earth observation datasets in Palar River basin, India

In this research we analyzed the morphometric parameter of Palar River basin by using the satellite data from open sources for monitoring drainage network. Palar River basin covers 1972.27 sq.km areas with elevation of 226.9 m as highest and 38.01 m lowest above mean sea level. In this research it detected that Palar River basin having 5th order stream with drainage density of 0.40 km/km2 and drainage pattern of dendritic to rectangular. We also draw aspect map, relief map and slope map for the research area by using digital elevation model (DEM) data of 30 m resolution. In this research we also employed spectral indices like normalized difference vegetation index (NDVI), normalized difference water index (NDWI), and soil adjusted vegetation index (SAVI) for the vegetation, water and soil characteristics of the research area. In this research it found that there are major changes in land use/land cover as water bodies and land during these periods of 15 years. Highly positive correlation show between morphometric parameter and spectral indices. In this research groundwater level data for the year 2005 and 2020 are used to validation the study. This research work is very useful in developing solutions for dealing with different types of drought and management of groundwater extraction plans.