Groundwater Management Strategies Research Articles

Identifying Groundwater Recharge Sources and Mechanisms using Hydrochemistry and Environmental Stable Isotopes in High Arsenic Holocene Aquifers of Bangladesh

Und erstanding the sources and mechanisms of aquifer recharge is critical for water resource management. So far, this is the first comprehensive study to explore the sources and mechanisms of groundwater recharge applying stable environmental isotopes and hydrogeochemical properties in Southwestern Bangladesh. Water samples from the different sources (groundwater, surface (pond), river and rain water) of high arsenic (As) Holocene aquifers were used to investigate the chemical tracers and environmental stable isotopes (δ18O and δ2H) to explore the hydrogeological features, groundwater recharge sources, mechanisms and processes. The analytical results showed high As concentration in water samples observed 590.7 μg/L. High As groundwater was identified by a low pH value, medium HCO3- and TDS with low concentration of NO3- and SO42-. However, depleted δ2H and δ18O signatures indicated that local vertical rainfall is the key source to recharge groundwater in study area. The recharge process from pond seepage and irrigation return flow also contribute in groundwater recharge. Isotopic signatures suggested the vertical connectivity amongst the aquifers and significant vertical recharge. The reduced heavier isotope reveals extra recharging from floods of mountains and high altitude. Due to the heterogeneous and anisotropic structure of the aquifer system the spatial variability of δ2H and δ18O shows limited lateral connectivity. The combined analyses of δ2H isotope and Cl- ion showed that evaporation is the primary cause for groundwater discharge. Based on the spatial and vertical recharge processes of groundwater, present study provides a crucial baseline knowledge for establishing a sustainable groundwater management strategy. The findings from this study can guide the development of targeted groundwater management strategies and improvement of understanding the groundwater recharge sources and processes.

Evaluating the impact of emerging hydro-geophysical technologies on sustainable water resource management

Emerging hydrogeophysical technologies are revolutionizing the management of water resources, providing unprecedented insights and enhancing sustainability practices. This article examines recent advancements in hydrogeophysical methods, focusing on time-lapse electromagnetic techniques, unmanned aerial vehicles (UAVs), and artificial intelligence (AI). Through a comprehensive review of the literature and practical case studies, including notable implementations in Africa, the paper highlights how these innovations improve groundwater monitoring, resource management, and predictive capabilities. Time-lapse electromagnetic methods have achieved up to 1-meter resolutions, significantly enhancing groundwater mapping accuracy (Binley & Kemna, 2005). With their high-resolution remote sensing capabilities, UAVs have facilitated detailed hydrological surveys, while AI-driven analyses optimize groundwater predictions and management strategies (Rennie et al., 2021). The study presents a cost-benefit analysis showing a 20-30% reduction in operational costs and a 40% increase in data accuracy. Challenges such as technical limitations and high initial costs are discussed, alongside potential solutions and prospects. The findings underscore the transformative potential of these technologies for achieving sustainable water resource management, offering actionable insights for policymakers, researchers, and practitioners in the field.

Groundwater resilience, security, and safety in the four largest cities in Denmark

Denmark's complete reliance on groundwater for water supply presents a unique case study in management of natural resources, urban planning, and water resilience in the face of climate change. This paper examines the groundwater management strategies in Denmark in general, focusing on Denmark's four largest cities—Copenhagen, Aarhus, Odense, and Aalborg— each facing distinct challenges due to their demographic, geographical, hydrogeological, and economic characteristics. Through analysis of these cities' approaches to groundwater management, this research contributes to the global discourse on sustainable urban water supply systems. As coastal groundwater cities (CGC), these urban areas must navigate the complexities of sustaining growing populations, mitigating climate change impacts, and coastal processes while ensuring the long-term viability of their groundwater resources. Copenhagen and Aalborg, built atop semi-confined fractured and locally karstic carbonate rocks, highlights the specific challenges associated with karstic groundwater systems, while, Aarhus, and Odense built on glaciofluvial aquifers faces different issues. The different groundwater challenges in these cities underscores the importance of integrating urban development with water resource management and environmental sustainability, offering valuable insights and lessons learned for other regions facing similar challenges. This study, thus not only sheds light on Denmark's groundwater management practices, but also emphasizes the need for innovative solutions to ensure the resilience of urban water supply systems in a changing climate and increasing pressures of emerging organic contaminants and elevated concentrations of geogenic elements induced by water abstraction and fluctuating water tables. Advanced Danish monitoring and modelling tools applied to support decision-making and innovation within the water sector are continuously developed and improved to support resilient and sustainable management of the available water resources.

Pollution risk evaluation of groundwater wells based on stochastic and deterministic simulation of aquifer lithology

Groundwater pollution risk evaluation is an important basis for developing groundwater protection measures and management strategies, and its accuracy directly affects the effectiveness of protection measures. The heterogeneity of the aquifer significantly affects the transport process of pollutants, increasing the uncertainty of pollutant risk assessment. However, in the actual site, borehole data that reveal aquifer heterogeneity are costly, and only a limited number of borehole data are available, which cannot accurately describe the heterogeneity of the aquifer, thus limiting the accuracy of groundwater pollution risk assessment. In order to overcome the above problems, this paper proposes a groundwater pollution risk assessment framework based on the stochastic and deterministic simulation of aquifer lithology. Based on the statistical characteristics of the change of lithology type in the actual borehole, the framework uses Markov chain to generate some sets of random lithology field and transforms them into heterogeneity parameter field, so as to realize the stochastic assessment of the pollution risk of groundwater resource wells. Furthermore, combined with the pumping test data, the parameter field that is most suitable for the actual situation is selected to evaluate the pollution risk deterministically. Finally, the stochastic and deterministic results are combined to comprehensively evaluate the pollution risk of groundwater resource wells. Through a case study in a river valley plain, the feasibility of the above framework is verified, and good application effects are achieved. This study provides a feasible method for accurately assessing groundwater pollution risk, which is helpful to reduce the impact of uncertain factors on pollution risk assessment, and thus provides a more reliable basis for groundwater management and decision-making.

Analysis of the Spatial Distribution of Seawater Intrusion Using a Hydrogeochemical Approach: A Study of the Coastal Geology of Kebumen Regency, Indonesia

This study examines seawater intrusion in the southern part of Kebumen District, focusing on the impact of various geological formations on groundwater salinity. Groundwater samples were systematically collected from 11 locations representing alluvial, volcanic, coastal sediment, and karst geological conditions. The samples were analyzed for major ions, including calcium (Ca²⁺), magnesium (Mg²⁺), chloride (Cl-), and bicarbonate (HCO₃-), as well as Total Dissolved Solids (TDS). Ion ratios such as Mg²⁺/Ca²⁺, Cl⁻/HCO₃⁻, and Mg²⁺/(Mg²⁺+Ca²⁺), along with the Fraction of Seawater (fsea), were calculated to assess the extent of seawater intrusion. The study employed the Gibbs diagram method to identify the primary processes controlling groundwater chemistry, revealing that water-rock interactions are dominant in most samples, particularly in those affected by seawater intrusion. The results indicate significant seawater intrusion in alluvial and karst regions, especially at sampling points TP 2, TP 4, and TP 10, while volcanic and coastal sediment areas show minimal intrusion. These findings underscore the critical influence of geological conditions on seawater intrusion and highlight the need for targeted groundwater management strategies. Further research focusing on long-term monitoring is recommended to better understand and mitigate the impacts of seawater intrusion in this region.

Multivariate Geostatistics for Mapping of Transmissivity and Uncertainty in Karst Aquifers

Due to their complex morphology, karst terrains are particularly more fragile and vulnerable to environmental damage compared to most natural systems. Their hydraulic properties, such as their transmissivity (T) and spatial variability, can be relevant for understanding groundwater flow and, consequently, for the sustainable management of water resources. The application of geostatistical methods allows for spatial interpolation and mapping based on observations combined with uncertainty quantification. Direct measurements of T are typically scarce, while those of the specific capacity (Sc) are more frequent. We established a linear and spatial relationship between the logarithms of T and Sc measured in 174 wells in a semi-arid karst region in northeastern Brazil. These relationships were used to construct a cross-variogram, whose Linear Model of Coregionalization proved valid. The values and the cross-variogram of logT and logSc were used to generate interpolations over 2554 values of logSc, which did not spatially coincide with logT. We used ordinary co-kriging (CO-OK) and conditional sequential Gaussian co-simulation (CO-SGS) to generate the interpolations. The cross-variogram of logT and logSc, when considering 174 wells, was isotropic with an exponential structure, a nugget effect of approximately 20% of the sill, and a range of 5 km. Cross-validation indicated an optimal number of 10 neighboring wells used in CO-OK, and we used 500 stochastic realizations in CO-SGS, which were then used to generate maps of logT estimates, deviations derived from the interpolations, and probabilistic scenarios. The resulting transmissivity maps are relevant for the design of groundwater management strategies, including stochastic approaches where the transmissivity realizations can be used to parameterize multiple executions of numerical flow models.

Investigation of aquifer storage properties and groundwater contamination risk potential using an electrical resistivity technique: a sedimentary environment case study

ABSTRACT There are growing worries regarding sufficient supplies of safe water in Obot Akara and Ikot Ekpene Local Government Areas of Akwa Ibom State. Thus, this study aims to investigate aquifer storage properties and contamination risk potential using electrical resistivity techniques in the two counties. The counties are shown to comprise 3–4 lithological successions of sandy and gravelly layers with slight clay intercalations. Groundwater abstraction takes place in the third and fourth layers in the area at depths between 5.4 and 121.4 m. The results demonstrate that the aquifer's prolificacy requires a specific yield larger than 0.15 or a specific retention less than 0.15. 94% of the study region is revealed to have good groundwater potential for the sustainability of water boreholes. Furthermore, the results show that 87.5% of the study region has weak/poor protection while 12.5% has moderate protection against infiltrating contaminants. In terms of susceptibility potential rating, 21.9% of the area has a moderate rating while the remaining 78.1% has a low rating. The identified areas with weak/poor protection and moderate susceptibility are adjudged to have moderate/high groundwater contamination risk potential. These findings provide valuable guidelines for formulating sustainable groundwater utilization and management strategies in the area.

Synthesizing vulnerability indices within a diverse lithological context: Corollaries for groundwater quality assurance and surface layer corrosiveness of Lokoja Geomaterials, Nigeria

ABSTRACT This study provides prototypical evaluation of groundwater vulnerability to contamination and soil corrosivity in Lokoja region, central Nigeria. By combining the aquifer vulnerability index, integrated electrical conductivity, groundwater confinement overlying strata depth to water table (GOD), and electrical anisotropy coefficient (λ) derived from lithological composition, resistivity, and layer thickness; the study identifies substantial vulnerabilities in the groundwater resources. Findings indicate that over 70% of the region is moderately to very highly vulnerable to groundwater pollution, especially in the eastern and southern parts, highlighting the need for tailored groundwater management strategies in highly vulnerable areas, covering 40% of the region. Corrosion potential varies spatially, with 80% of the upper layer being minimally corrosive and around 45% of the lower moisture-rich layer showing moderate to significant corrosiveness, emphasizing risks in central and northern zones associated with lithological compositions and moisture content. These accentuate the necessity of rigorous monitoring programs and strict land use regulations to protect aquifers and infrastructure. This research underscores the value of proactive management for safeguarding groundwater resources, providing an invaluable framework for decision-making and resource allocation to tackle contamination and corrosion risks. Importantly, the research addresses a significant research gap in a region with limited scientific exploration.

Major Ions and Trace Elements Characterization of Groundwater in Shallow Aquifers, Yaoundé Urban City, Cameroon

Purpose: This study assessed the suitability of groundwater in parts of Yaoundé city for drinking and domestic purposes, investigating the factors controlling its composition. Materials and Methods: Water samples were collected during the dry season and analyzed for physicochemical parameters and major ions. Findings: Results showed an acidic aquifer with generally fresh water, dominated by Ca-HCO3, Na-Cl, Ca-NaHCO3, and Ca-Cl water types. While most major ions were within WHO guidelines, nitrates exceeded safe limits in most samples, and some trace elements like aluminum, manganese, and iron were also above recommended levels. Implications to Theory, Practice and Policy: The study concludes that groundwater quality is influenced by water-rock interaction, ion exchange, and anthropogenic activities, particularly nitrate and chloride pollution. Therefore, proper groundwater management strategies are crucial to ensure the sustainability and safety of this vital resource.

Assessment of groundwater level fluctuation using integrated trend analysis approaches in the Kapran sub-basin, North East of Iraq

Groundwater extraction in the Kapran Sub-basin (KSB) has been intensified in recent decades due to population growth, urbanization, industrial activities, and agricultural expansion. Assessing water resources in KSB has become vital for researchers and local authorities to develop sustainable groundwater management strategies. This study aims to evaluate the spatio-temporal changes and trends of groundwater level using Innovative Trend Analysis (ITA), supported by non-parametric test techniques like Mann-Kendall (MK), modified Mann-Kendall (mMK) and Sen's slope estimator, along with Cumulative Rainfall Departure (CRD) to assess the relationship between groundwater level fluctuations and rainfall-recharge. Data from 10 monitoring wells (2000–2023), three rainfall stations (1941–2022), and 1053 production wells (2008 and 2023) were analyzed using geostatistical method. The results illustrate a strong linear relationship between the water level and topography, highlighting the aquifer's heterogeneity. The ITA and non-parametric analysis reveal a significant decline in groundwater levels, exacerbated by reduced rainfall (0.05–1.89 mm/year) and increased extraction (1.0 × 10^6 m³/day), with a decline rate ranging from 0.7 to 5.4 m/year. These findings provide (1) a robust scientific foundation for the stakeholders to efficiently develop sustainable strategies for integrated water resource management (IWRM) in order to mitigate the effect of climate change and GW abstraction, and (2) it provides local authorities and government in resolving groundwater scarcity in KSB.

Estimation of Groundwater Recharge in a Volcanic Aquifer System Using Soil Moisture Balance and Baseflow Separation Methods: The Case of Gilgel Gibe Catchment, Ethiopia

Understanding the recharge–discharge system of a catchment is key to the efficient use and effective management of groundwater resources. The present study focused on the estimation of groundwater recharge using Soil Moisture Balance (SMB) and Baseflow Separation (BFS) methods in the Gilgel Gibe catchment where water demand for irrigation, domestic, and industrial purposes is dramatically increasing. The demand for groundwater and the existing ambitious plans to respond to this demand will put a strain on the groundwater resource in the catchment unless prompt intervention is undertaken to ensure its sustainability. Ground-based hydrometeorological 36-years data (1985 to 2020) from 17 stations and satellite products from CHIRPS and NASA/POWER were used for the SMB method. Six BFS methods were applied through the Web-based Hydrograph Analysis Tool (WHAT), SepHydro, BFLOW, and Automated Computer Programming (PART) to sub-catchments and the main catchment to estimate the groundwater recharge. The streamflow data (discharge) obtained from the Ministry of Water and Energy were the main input data for the BFS methods. The average annual recharge of groundwater was estimated to be 313 mm using SMB for the years 1985 to 2020 and 314 mm using BFS for the years 1986 to 2003. The results from the SMB method revealed geographical heterogeneity in annual groundwater recharge, varying from 209 to 442 mm. Significant spatial variation is also observed in the estimated annual groundwater recharge using the BFS methods, which varies from 181 to 411 mm for sub-catchments. Hydrogeological conditions of the catchment were observed, and the yielding capacity of existing wells was assessed to evaluate the validity of the results. The recharge values estimated using SMB and BFS methods are comparable and hydrologically reasonable. The findings remarkably provide insightful information for decision-makers to develop effective groundwater management strategies and to prioritize the sub-catchments for immediate intervention to ensure the sustainability of groundwater.

Spatial downscaling of GRACE-derived groundwater storage changes across diverse climates and human interventions with Random Forests

The Gravity Recovery and Climate Experiment (GRACE) satellites launched in 2002, which were followed by the GRACE Follow-On mission in 2018, represented a significant advancement in global groundwater storage monitoring. However, the inherent limitation of a relatively low spatial resolution confines its applicability primarily to large river basins and aquifers. This study introduces a novel statistical downscaling approach using Random Forests (RF) to enhance the spatial resolution from 3° × 3° to 0.25° × 0.25° for GRACE-derived groundwater storage (GWS) changes. Focusing on sub-Saharan Africa, the Middle East, and South Asia across diverse climates and human interventions, the analysis spans from February 2003 to December 2022. Predictors encompass hydrological fluxes and their accumulation, including IMERG precipitation, GLEAM evapotranspiration, and GLDAS runoff, alongside GLDAS soil moisture and MODIS NDVI. RF models show robust performance across 114 aquifers, with a Pearson’s correlation coefficient (CC) exceeding 0.92 for training sets and 0.85 for validation sets. Validation against in-situ groundwater level observations from wells in India reveals satisfactory performance, with positive Spearman’s CC values between in-situ groundwater levels and downscaled terrestrial water storage anomaly (TWSA) for a majority of dug and bore wells. This study concludes with the generation of monthly downscaled GWS changes (0.25° × 0.25°) spanning from February 2003 to December 2022. These datasets serve as a foundation for facilitating finer-scale hydrological studies and formulating local groundwater management strategies.

Groundwater contamination modelling in Ayad River Basin, Udaipur

Groundwater, a vital freshwater resource catering to agricultural, domestic, and industrial needs, faces a pressing challenge of contamination due to escalating human activities. This study focuses on the Ayad River Basin in the Udaipur district of Rajasthan, employing the FEFLOW simulation code for the first time. A steady-state numerical model and a groundwater contaminant prediction model for total dissolved solids (TDS), nitrate, and fluoride were developed, simulating trends over the next five years with an accuracy exceeding 95%. The results reveal an eastward increase in TDS, nitrate, and fluoride concentrations, attributed to contamination from two waste disposal sites-Titadi and Baleecha. Titadi, operational for four decades until closure in 2010, retains residual waste over 32 thousand m2. The initiation of a new dumping ground at Baleecha by the Udaipur Municipal Corporation post-2010 exacerbates regional contamination. Nitrate contamination is particularly high in agricultural zones with excessive chemical fertilizer usage. Of the 27 scenarios tested, 23 support using the water for irrigation but would require treatment before using it for drinking. Recommendations include deploying a chemical sensor network for real-time data input into the web enabled FEFLOW model, real-time monitoring and alerts, and a mobile application providing personalized guidance on water usage and health risks in case of contamination. This study can be beneficial to decision-makers, who work on the policy and groundwater management strategies.

Investigation of Heavy Metal Composition and Associated Health Risks from Selected Groundwater Wells in Temeke, Dar-es-Salaam

Water quality continues to be the challenge to residents in Dar es Salaam due to various anthropogenic activities in the city. This study was conducted to assess groundwater quality by determining concentrations of heavy metals. Both probability and Nonprobability sampling techniques were used to collect samples from 40 groundwater wells in 24 wards of Temeke municipal and analysed using Microwave Plasma Atomic Emission Spectrometer (Agilent 4210 MP-AES) at the Geochemistry Laboratory of the University of Dar es Salaam. Results indicated varying heavy metal concentrations ranging from 0.71 ± 0.08 to 6.64 ± 0.21 mg/l for As, 0.02 ± 0.01 to 0.07 ± 0.01 mg/l for Co and 0.16 ± 0.01 to 0.02 ± 0.01 mg/l for Pb. The As, Co and Pb concentrations exceeded (P < 0.05) the recommended TBS standards of 0.05 mg/l, 0.003 mg/l and 0.01 mg/l respectively. Other concentrations ranged from 0.01 ± 0.01 to 0.88 ± 0.01 mg/l for Cu, 0.02 ± 0.01 to 3.55 ± 0.02 mg/l for Fe, 0.00 ± 0.00 to 4.63 ± 0.03 mg/l for Mn and 0.01 ± 0.01 to 3.00 ± 0.01 mg/l for Zn. The Cu, Fe, Mn and Zn concentrations were below (P > 0.05) the allowable TBS limits of 0.05 mg/l, 0.3 mg/l, 0.1 mg/l and 3 mg/l respectively. Health risk analysis revealed potential adverse health effects from long term consumption of As, Mn and Pb with Hazard Quotient exceeding 1 (HQ > 1). The Hazard Index (HI) for all groundwater samples was also above 1 (HI > 1) indicating a higher likelihood of adverse health effects. The study concluded that groundwater wells in Temeke Municipal are affected through natural and anthropogenic activities leading to high levels of heavy metal concentrations. Also, this study provides valuable information on risk associated by continued usage of groundwater in Temeke region and hence informs respective stakeholders on groundwater quality and potential risks thereby emphasizing the need for remedial measures and stricter regulations to safeguard public health. The study recommends the need for regular groundwater quality and safety monitoring to assess the levels of heavy metals concentrations and implement sustainable groundwater management strategies to address the increasing water demand in Temeke municipal, Dar es Salaam.

Appraising seawater intrusion in the Moroccan Ghiss-Nekor coastal aquifer: Hydrochemical analysis coupled with GIS-based overlay approach

Seawater intrusion (SWI) into coastal aquifers poses a significant environmental problem, and identifying an effective method to assess its extent is challenging. This study introduces a method for accurately delineating the extent of SWI in the Ghiss-Nekor aquifer, using a dual approach of hydrogeochemical analyses and geospatial technologies. We used several geochemical markers, including four ionic ratios (Cl-/HCO3-, SO42-/Cl-, Na+/Cl-, and Mg2+/[Mg2++Ca2+]) along with two SWI indices (GQIswi and SMI). These markers were interpolated and subsequently overlaid using GIS-based overlay analysis, enabling us to generate an accurate map pinpointing areas affected by SWI. The study reveals that SWI affects roughly 20 % of the investigated region, with 70 % of these cases found within 2 kilometers of the coastline. The detection of saline water as far as 5 kilometers inland, as explained by the aquifer’s geological model, points to SWI emanating from the Souani area, infiltrating through coarse sand and gravel located above the impermeable deep clay-marly strata. These outcomes validate our hydrogeochemical method and offer essential data about SWI’s scope. Such insights are indispensable for policymakers in the Al Hoceima area to forge effective groundwater management strategies in response to climate change-induced challenges like diminishing water resources from reduced rainfall.

Groundwater sustainability mapping for managed aquifer recharge in Dwarkeswar River basin: Integration of watershed modeling, multi-criteria decision analysis, and constraint mapping

Groundwater sustainability is a pressing issue in many regions, especially in semi-arid and drought-prone areas, impacting progress towards achieving the Sustainable Development Goals (SDGs). This study addresses this challenge by assessing Managed Aquifer Recharge (MAR) potential in India's Dwarkeswar River basin. The study employs a systematic approach integrating watershed modeling using the Soil and Water Assessment Tool (SWAT), multi-criteria decision analysis (MCDA), and constraint mapping techniques. Initially, the SWAT model evaluates water availability for MAR, followed by an MCDA-AHP method to identify optimal sites based on ten spatial parameters encompassing technical, economic, and environmental criteria. Furthermore, the study employs constraint mapping to refine site suitability assessments and sensitivity analysis to gauge the robustness of the results. The SWAT analysis revealed substantial variation in runoff volumes among the eight sub-basins, ranging from 8.34 m³/s to 136.28 m³/s, indicating significant availability of source water for MAR. Results from the MCDA followed by constraint mapping indicate that 51.57% of the study area is unsuitable for MAR, while 0.12%, 34.59%, and 13.72% are classified as low, moderate, and suitable zones, respectively. Sensitivity analysis reveals that geological attributes, soil thickness, runoff, and slope significantly influence the suitability scores, underscoring their impact on MAR feasibility. Validation with major pond locations confirmed the accuracy of this integrated approach in identifying suitable sites for MAR initiatives. This emphasizes the importance of holistic groundwater management strategies for sustainable water resource utilization and achieving the SDGs.

Groundwater evolutions in the semi-arid aquifers of Dodoma City, Tanzania using stable isotopes of water and hydrogeological facies

ABSTRACT The recent influx of people into Dodoma City, Tanzania has greatly increased pressure on freshwater sources. To manage such stressed water resources, an assessment of evolutions of various groundwater masses using stable isotopes (SI) and hydrogeochemical facies was performed. The major groundwater types were found to be NaHCO3 and NaCl. The groundwater in some areas was polluted with up to 223.7 ppm of nitrate-NO3-. The majority of water masses were found to be of meteoric origin and deep aquifers were mostly replenished by heavy rains, which are more depleted in SI (δ2H and δ18O). Further, δ2H and δ18O from Hombolo Dam (HD) and Matumbulu Dam (MD) were highly enriched by evaporation, with average δ2H and δ18O values, of 5.76 & 39.69 and 2.37 & 16.34 ‰ compared to average rain values of −5.52 and −32.99‰, respectively. The contributions of highly enriched HD and MD waters to respective shallow groundwater systems were 57.52 and 22.2%. Yet, it was found that 75.4% of groundwater in the Hombolo suburb originates from the Makutupora aquifer, and this is the first time the contribution is quantified. Generally, this study offers a robust tool for adapting a local groundwater management strategy impacted by climate change, pollution, and overabstraction.

Hydrogeochemical Investigation and Estimation of Aquifer Properties at Dhaka University Campus

The University of Dhaka has its own water supply system and entirely relies on groundwater. Ten groundwater samples were collected from 10 production wells of 120-320 m depth across the University campus from upper and lower Dupi Tila aquifers. The pH values revealed that water is mildly acidic to neutral and electrical conductivity (EC) values ranging from 325 to 654 μS/cm, indicating fresh groundwater. The total hardness (TH) of the samples ranges from 76-203 mg/L, suggesting moderately hard to very hard water. Of the ten groundwater samples, nine are of Ca-Mg-HCO3 type, whereas one shows Ca-Na-HCO3 type of groundwater. The saturation indices show that the groundwater samples are near-saturated for calcite, dolomite, gypsum, siderite, and rhodochrosite, indicating the low potential for dissolution-precipitation of these mineral. Notably, the results of WQI indicate that all the wells are safe for drinking. As of July 2023, the groundwater level was 72 m below ground level with a declination rate of 2.8 m/year. The estimated hydraulic conductivity values of 20 to 90 m/day and transmissivity values of 637 to 2740 m²/day suggest better permeability and water transmission potential within the lower aquifer. These results provide essential information for the university authority to implement appropriate strategies for efficient groundwater management. The Dhaka University Journal of Earth and Environmental Sciences, Vol. 12(2), 2023, P 55-67

Groundwater Potential Zone Assessment Using Remote Sensing, Geographical Information System (GIS), and Analytical Hierarchy Process (AHP) Techniques in Fogera Woreda, South Gondar Zone, Ethiopia

The study was conducted to know the groundwater potential zones in Fogera Woreda, south Gondar zone, Ethiopia. Through the utilization of the analytical hierarchy process (AHP), remote sensing, and geographic information system (GIS), the study identified groundwater potential zones. Ten thematic layers were analyzed to delineate the groundwater potential zones, including land use and land cover (LULC), topographic wetness index (TWI), drainage density, lineament density, geology, slope, rainfall, elevation, and soil texture. By determining the relative importance of each thematic layer through AHP and combining all thematic layers through overlay analysis in a GIS environment, the study revealed a spatial variation in the distribution of groundwater potential zones. The results showed that excellent groundwater potentials cover 2.02% of the study area, moderate groundwater potentials cover 45.54%, poor groundwater potentials cover 51.2%, and extremely poor groundwater potentials cover 1.24% of the study area. The study provides valuable information that can be used for decision-making processes and the development of appropriate groundwater management strategies in the region.

Exploring groundwater depletion and land subsidence dynamics in Taiwan’s Choushui river alluvial fan: insights from integrated GNSS and hydrogeological data analysis

The Choushui River Alluvial Fan (CRAF) is a major agricultural area in Taiwan with heavy groundwater usage. The extraction of groundwater here has caused land subsidence, which is now a significant global environmental issue. This study analyzes land subsidence in the CRAF by integrating hydrogeological data from 233 groundwater monitoring stations across four aquifers (CRAF Groundwater_NET) and data from 50 continuous GNSS stations (CRAF GNSS_NET). We developed an automated processing flow for GNSS static surveying within CRAF GNSS_NET, and further employed a time-series fitting method to examine the long-term trends and annual changes for both GNSS and groundwater level data. Our analysis of the time-series data from the past decade identifies areas of significant groundwater level depletion and subsidence hotspots. We explore the relationship between groundwater level variations and surface displacements within CRAF, utilizing GNSS data to analyze horizontal and vertical displacement trends, as well as annual changes. We integrate these findings with hydrogeological data to understand regional subsidence patterns. Our results indicate that CRAF is characterized by distinct hydrogeological features. The study finds that the amplitudes of annual changes in both groundwater level and vertical displacement generally increase from northeast to southwest in the analyzed region. One particular area shows significant groundwater level decline, with the most severe rate recorded at 0.54 m/year. Similarly, GNSS analysis indicates pronounced subsidence trends in the same area, with rates ranging from 4.2 to 5.2 cm/year. These findings highlight the critical need for the development of effective groundwater management strategies to ensure sustainable use of groundwater resources and to implement mitigation measures against land subsidence in similar multiple-aquifer settings.