Aquifer Vulnerability Assessment Research Articles

GIS-based assessment of aquifer vulnerability using DRASTIC model and stable isotope: a case study on Essaouira basin

Groundwater in the present study is defined as a sensitive contamination of fresh water to various pollutants that are made by human or natural elements. The research sought to measure the vulnerability of groundwater in the semi-arid regions and to identify sites where protection is likely needed by way of examining the resources relative to the sources of pollutants in the Meskala–Krimat sub-basin by using the DRASTIC model in the Geographic Information System (GIS) environment. The DRASTIC index resulting from the groundwater modeling that ranges between 114 and 191 were classified into three categories: low vulnerability which signifies 1.7% confidence level, moderate vulnerability which signifies 14.7% confidence level, and high vulnerability which signifies 83.7% confidence level. Analyzing this approach disclosed the electrical conductivity from the upstream part increased compared with the downstream part of the study area due to susceptibility to the high mineralization and leaching of Tidzi Diapir. In addition, the groundwater flow remained in the same direction from northeast to northwest and from northeast to southwest during the four campaigns 2007, 2018, 2019, and 2020. Stable isotope (2H and 18O) measurements indicate that the Atlantic rainfall is continuously recharging the watershed recharge areas. And so, the low values of tritium (3H) in the groundwater signify that the fresh water in the Cenemano-Turonien aquifer is old. The present study proved that DRASTIC modeling using GIS is an effective technique in managing and protecting the vulnerable groundwater.

New hybrid-based approach for improving the accuracy of coastal aquifer vulnerability assessment maps

Due to excessive exploitation, groundwater resources of coastal regions are exposed to seawater intrusion. Therefore, vulnerability assessments are essential for the quantitative and qualitative management of these resources. The GALDIT model is the most widely used approach for coastal aquifer vulnerability assessment, but suffers from subjectivity of the identification of rates and weights. This study aimes at developing a new hybrid framework for improving the accuracy of coastal aquifer vulnerability assessment using various statistical, metaheuristic, and Multi-Attribute Decision Making (MADM) methods to improve the GALDIT model. The Gharesoo-Gorgan Rood coastal aquifer in northern Iran is used as study site. In order to meet this aim, the Differential Evolution (DE) and Biogeography-Based Optimization (BBO) metaheuristic algorithms were employed to optimize the GALDIT weights. In addition, a novel MADM method, named Step-wise Weight Assessment Ratio Analysis (SWARA), and the bivariate statistical method called statistical index (SI) were used to modify the GALDIT ratings. Finally, correlation coefficients between the maps obtained from each method and Total Dissolved Solid (TDS) as an indicator of seawater intrusion were computed to evaluate the models' prediction power. Correlation coefficients of 0.72, 0.75, 0.76 and 0.78 were obtained for the GALDITSWARA-BBO, GALDITSI-BBO, GALDITSWARA-DE and GALDITSI-DE models, respectively. The results from the GALDITSI-DE model outperformed all other models at improving the accuracy of the vulnerability assessment. Moreover, the statistical-metaheuristic method yielded more accurate results than SWARA-metaheuristic hybrid models. The vulnerability map of the studied region indicates that the northwestern and western areas are very highly vulnerable. According to GALDITSI-DE model, 42%, 17%, 18% and 22% of the aquifer areas respectively have a low, medium, high and very high vulnerability to seawater intrusion. The research findings could be applied by regional authorities to manage and protect groundwater resources.

Groundwater Occurrence and Aquifer Vulnerability Assessments in Coastal Settlements of Araromi Seaside and its Environ, Southwestern Nigeria

The groundwater potential and aquifer vulnerability study of Araromi Seaside are reported in this study using a combination of Vertical Electrical Sounding (VES) and Electrical Resistivity Tomography (ERT). Double dipole with minimum electrode spacing of 20 m and maximum length of 400 m were employed to acquire twelve (12) ERT data while Schulumberger configuration with maximum half current electrode separations of 500 m was used to obtain the twelve (12) VES data at the mid-point of each ERT traverse. ERT data was inverted using DIPPRO for window software why VES curves were iterated using WINRES software. Interpretation of the ERT results show promising groundwater potential points under ERT line 1, 4, 6, 8, 11 and 12, while the VES result revealed good sandy / clayey sand aquifers with good aquifer thickness under VES 1, 2, 3, 6, 7, 10, 11 and 12. In terms of aquifer vulnerability capacity, VES 3, 5, 8 and 11 show poor capacity, VES 10 and 12 weak capacity, VES 2, 4, 7 moderate and VES 1, 6, 9 show good capacity. For healthy water supply, groundwater boreholes should be developed in areas with good aquifer parameters and good protective capacity. Juxtaposing the two parameters we suggested VES 1, 2, 6 and 7 which have both groundwater potential and vulnerability capacity for groundwater borehole development. Considering spatial result that the ERT affords, other possible point like surface position 170 m on Profile 4 is also recommended, because it satisfies the two conditions of good aquifer and good vulnerability capacity.

Vulnerability Identification of Hajiabad Plain Aquifer: The DRASTIC Model and the GIS-Based Fuzzy Logic Method

Hajiabad plain with an area of about 158 km2 is located about 160 km north of Bandar Abbas in Iran. Due to the significance of this plain in terms of agricultural and drinking water supply in the region and the declining groundwater level in the region, the withdrawal of water resources has been prohibited in recent years. The purpose of this study is to determine the vulnerability of the aquifer using the DRASTIC model and the optimal method of fuzzy logic as well as the drastic method calibrated with nitrate. Finally, the final vulnerability maps were calibrated with EC values. In order to investigate the hydrogeochemical properties of groundwater resources of the plain, 26 water samples were collected from designated points in different periods of the water year 2018. Water samples were analyzed in Hormozgan soil and water laboratory. Also, the results of water sample data analyzed by Hormozgan Regional Water Organization were used. Assessment of aquifer vulnerability based on vulnerability models showed that the east and parts of the center of the plain were subject to the highest vulnerability, while the southern, southwestern, and northern slopes of the plain were of the lowest vulnerability. The determined coefficients between nitrate and DRASTIC vulnerability models and fuzzy optimization were estimated to be 0.41 and 0.36, respectively. Nitrate concentration validation demonstrated that the vulnerabilities of Hajiabad plain aquifer were almost similar under both drastic model and fuzzy optimization methods.

Integration of GIS and F-Hydra Model for Aquifer Vulnerability Monitoring in the Afram Plains, Ghana

Aquifer vulnerability is a critical issue across the entire globe due to the depletion of groundwater and escalation of pollution levels, which poses a detrimental effect on the natural environment. To ascertain this contamination risk, an extensive study has been conducted to assess the aquifer vulnerability by using the F-hydra model. This paper presents the vulnerability technique for the theory and application of flow accumulation, land-use and hydraulic conductivity. The model was applied to a shallow aquifer in eastern Ghana’s Volta River Basin, with the results being compared to the standardised DRASTIC model. The model follows the aquifer vulnerability assessment concept of the source pathway receptor where flow accumulation represents the ponding areas with downward percolation of contaminant to the water table, land-use represents the human activities at the land surface, and hydraulic conductivity represents the driving force leading to the movement of contaminant. The results reveal that the moderate vulnerability region covers 51.55% (2598.12 km2) of the entire area. The high and low vulnerability regions cover a significant percentage of the area 1.13% (56.52 km2) and 47.32% (2384.93 km2), respectively. The final vulnerability index was largely influenced by the removal of the hydraulic conductivity and land-use parameters. The model was validated with nitrate concentration in drilled wells in the study area. The maps produced in this study could be utilised as a guide to vulnerability by policymakers, groundwater manager and planners aimed at preserving the integrity of this vulnerable resource.

Water vulnerability of coastal aquifers using AHP and parametric models: methodological overview and a case study assessment

The concept of groundwater vulnerability is a useful tool for environmental planning and decision-making. Added to overexploitation, the increasing agricultural activities have affected water resources. The groundwater contamination is becoming an important issue, especially in coastal areas also threatened by seawater intrusion. Indeed, several methods have been developed for assessing aquifer vulnerability. This study aims to develop a comparison between the application of the DRASTIC and GALDIT standard parametric models and the AHP-DRASTIC and AHP-GALDIT combined models in order to evaluate the groundwater vulnerability in the Mahdia-Ksour Essef coastal aquifer. For a better highlighting the spatial visualization of the obtained results, we used the GIS technics. The results showed that the coastal zone is the most susceptible to the seawater intrusion. The correlation coefficients showed that the relationship between the DRASTIC and AHP-DRASTIC vulnerability indexes and the nitrate concentration was increased from 28 to 57%, respectively. Furthermore, the correlation coefficients showed that the relationship between the GALDIT and AHP-GALDIT vulnerability indexes and the electrical conductivity was increased from 41 to 69%, respectively. This requires the use of the AHP-GALDIT combined method which is considered more effective and provides good results. Obtained results could be considered as a guide for the groundwater management.

GROUNDWATER VULNERABILITY ASSESSMENT USING DRASTIC MODEL OF UP AL-KHASSA DAM SUB-BASIN, KIRKUK, NE IRAQ

Several studies and assessments have been conducted of areas exposed to pollution, especially areas that contain aquifer. The final extraction of the vulnerability map of the groundwater was constructed through the use of the DRASTIC method by applying the linear equation of the seven coefficients in the Arc GIS software program (Version 10.4). The aim of the study to assess aquifer vulnerability to pollution. Results, vulnerability map range between 75-126 (very low, low, and medium), the study area consists of very low and low vulnerability, except some areas medium vulnerability close to the center of the sub-basin in the standard vulnerability map (s) and 91-149 (very low, low, and medium) for the agriculture or pesticide vulnerability map (p), the medium vulnerability occupies a greater area the center of the sub-basin.

Modelling the trends of resistivity gradient in hydrogeological units: a case study of alluvial environment

Generally, longitudinal resistance is identified as one of the second order geo-electric indices used to assess aquifer vulnerability to contamination; mapping of geologic sequence for location of engineering sites and evaluation of subsurface for mineral explorations based on the varying electrical characteristics. Geo-resistivity of vertical electrical sounding (VES) was performed to examine the variations of resistivity gradient for surficial geological lithologies in the alluvial environments. Fourteen VES employing Schlumberger electrode configuration with a maximum current spacing AB of about 300 m were performed. The VES data were reduced to its first order geo-electric indices, representing geologic equivalents of the layers penetrated by current with the constraints of nearby logged boreholes. The first order geo-electric indices were converted to second order geo-electric indices, which include longitudinal conductance and resistance. The injected current at its maximum electrode separations penetrated four sedimentary units characterized by resistivity range of 95.2–3455.5 Ωm and mean value of 834.8 Ωm in the first layer. In the second layer, the gamut of resistivity was found to be from 8.8 to 3606.6 Ωm while its average value was 1327.8 Ωm. In the third and fourth layers, the mean values of resistivities were 657.2 and 1551.2 Ωm while their ranges were 72.5–1464.5 Ωm and 117.1–4893.0 Ωm respectively. Two sets of reflection coefficients estimated between layers 1 and 2 and 2 and 3 were determined and used to assess the trend of distribution of the geologic units, which indicated that the layers are alternating with argillites and arenites. Both the longitudinal conductance and resistance estimated indicate that the assessed alluvial environments are on the average, vulnerable to contaminations.

Assessing Specific Vulnerability of Shallow Aquifers to Pesticide Using GIS Tools. Data Needs and Reliability of Index-Overlay Methods: An Application to the San Giuliano Terme Agricultural Area (Pisa, Italy)

Pesticides play a crucial role in regulating crop production by reducing crop losses and increasing crop yield and quality. However, they may threaten surface and groundwater, a phenomenon occurring at global scale, potentially causing environmental damage and prohibition of water use or high treatment costs for drinking water. Assessing spatially-defined aquifer vulnerability to pesticide is then important, as it may allow defining agricultural areas where pesticides should be used following well-defined agronomic practices/limitations. In this study, after a brief review of recent studies on aquifer vulnerability assessment to pesticide, we applied the Vulnerability Index method to the agricultural area of the Municipality of San Giuliano Terme (Pisa, Italy) in order to focus on the data needs and discuss the reliability of this method (as an example of index-overlay methods). The proposed method needs a relatively small number of parameters compared to other more complex ones. Despite a such a small number of parameters, some were not easily available in our case study. Thus, some assumptions were made. This led to vulnerability maps with reduced reliability, no validation with groundwater samples, and little practical use. This means that to produce robust but static vulnerability assessments, large datasets are needed. In turn, the cost of data gathering may be high. The value of these data may, however, be increased, and the cost better justified if the analyses are based on process-based or advanced statistical methods. While the future for vulnerability assessment methods is the use of process-based/advanced statistical methods, index-overlay methods, as a preliminary step for process-based simulation analysis, may still provide initial and relatively quick insights on potential leaching of pesticides. This in turn may support extension services in delivering timely and relevant advices on the use of such pesticides to farmers and owners of plant nurseries and greenhouses.

Determining the lake protected zones using GIS-based DRASTIC model to groundwater vulnerability in Salda Lake basin (Burdur/Turkey)

Groundwater quality is a crucial parameter for sustainable wetland management. The evaluation of the aquifer vulnerability is important for the protection of groundwater resources. The DRASTIC model is the most significant technique for the assessment of aquifer vulnerability. This study aimed to build a vulnerability map for groundwater of the Salda Lake wetland basin by DRASTIC method in a GIS environment. Seven environmental parameters (depth to water table, net recharge, aquifer media, soil media, topography, impact of the vadose zone media, and hydraulic conductivity of the aquifer) were used in the DRASTIC method and GIS was used to constitute a groundwater vulnerability map. This study showed that 13.71% of the area had high pollution potential, 10.13% had moderate pollution potential, and 76.15% had low pollution potential in respect to groundwater pollution. Intensive agricultural activities are carried out in the study area. The DRASTIC vulnerability index value of the study area was well correlated with the nitrate map of the study area. In addition, Salda Lake protection areas were determined. All of the defining protection areas of the Salda Lake are within the most sensitive areas in DRASTIC map.

Nitrate-leaching and groundwater vulnerability mapping in North Bihar, India

Aquifer vulnerability assessment is crucial for studying the impact of increasing pollution load scenarios on the quantification of contaminant concentration with movement of plume for protecting groundwater resources. Only a few recent studies have focused on the performance evaluation of vulnerability assessment methods using process-based modeling approach. However, the moisture flow and pollutant transport through partially saturated zone plays a crucial role under varying hydrogeological conditions, which are generally ignored in index-based methods. Thus, the objective of this research is to evaluate the vulnerability of groundwater resources to nitrate in Samastipur, Darbhanga and Madhubani districts of Bihar State, India, using soil moisture flow and solute transport modeling. Richard’s equation integrated with the classical advection dispersion equation is simulated using HYDRUS 1D by incorporating a constant head and atmospheric boundary conditions. The time taken to reach the nitrate peak concentration at groundwater table is considered to estimate vulnerability index (VI). Results have shown that high risk in terms of nitrate-leaching vulnerability in southern part of study area is dominated by Gangetic kankar in subsurface. Further, high pollution risk was reported in eastern north part of study area having alluvial deposition in subsurface. The main causes of high risk were due to the short depth of water table, little discharge and more hydraulic conductivity presence in the subsurface media. Moreover, comparatively low vulnerability was observed in area having clay capping of 2–4 m from surface. This research may help in better implementation of agricultural, soil–water conservation practices and urban/industrial infrastructure development in and around the study area.

ASSESSING AQUIFER VULNERABILITY AND CONTAMINANT PLUME AT ARTISANAL REFINING SITES IN PARTS OF OKRIKA AND OGU-BOLO LOCAL GOVERNMENT AREAS, RIVERS STATE, NIGERIA

This study aims at the assessment of aquifer vulnerability and contaminants plume where artisan refining of crude is taking place, which is a threat to availability of potable water. The ArcGIS version 10.3, ENVI version 4.7, Surfer 10, SPSS 22 and Microsoft Enterprise were used for the interpretation and the water and soil samples were analyzed in the laboratory using standard methods. A total number of sixteen (16) sampling points were selected using random sampling techniques for the water points and soil samples within Ogu Bolo and Okrika. The Digital Elevation Model was created from the elevation data obtained from SRTM (Short Radar Thematic Mapper) satellite image and contour extracted from the topographic map. The influence of the soil type, slope, flow accumulation, flow direction of the study area was used to delineate the level of contaminant plume. This was generated from the DEM using the ArcGIS 10.3 3-D analyst tool function. A water Quality index rating of 1 was measured in the study area which is an indication that the water is very bad. Also, the physiochemical analysis on soil and water revealed poor water and soil. Water analysis showed high concentration of Fe and Zn which made the water in the area unsuitable for drinking. Also, the soil samples recorded high levels of crude content from 1m, with concentration reducing with depth up to 3m. A general contamination map of Okrika/Ogu-bolo was modelled, indicating the contamination rating of the total land mass of the study area, with 23.59km (5.71%) rated very good, while 85.65km (20.71%) were rated good. Also, 140.37km (33.95%) had only showed moderate level of contamination while 112.56km (27.22%) recorded high level of contamination, with 51.29km (12.40%) of the total land mass having a very bad contamination record.

Tree-Based Modeling Methods to Predict Nitrate Exceedances in the Ogallala Aquifer in Texas

The performance of four tree-based classification techniques—classification and regression trees (CART), multi-adaptive regression splines (MARS), random forests (RF) and gradient boosting trees (GBT) were compared against the commonly used logistic regression (LR) analysis to assess aquifer vulnerability in the Ogallala Aquifer of Texas. The results indicate that the tree-based models performed better than the logistic regression model, as they were able to locally refine nitrate exceedance probabilities. RF exhibited the best generalizable capabilities. The CART model did better in predicting non-exceedances. Nitrate exceedances were sensitive to well depths—an indicator of aquifer redox conditions, which, in turn, was controlled by alkalinity increases brought forth by the dissolution of calcium carbonate. The clay content of soils and soil organic matter, which serve as indicators of agriculture activities, were also noted to have significant influences on nitrate exceedances. Likely nitrogen releases from confined animal feedlot operations in the northeast portions of the study area also appeared to be locally important. Integrated soil, hydrogeological and geochemical datasets, in conjunction with tree-based methods, help elucidate processes controlling nitrate exceedances. Overall, tree-based models offer flexible, transparent approaches for mapping nitrate exceedances, identifying underlying mechanisms and prioritizing monitoring activities.

Meta-heuristic algorithms in optimizing GALDIT framework: A comparative study for coastal aquifer vulnerability assessment

Creating a reliable groundwater vulnerability map is a key solution for protecting the groundwater resources and further planning in coastal aquifers. The GALDIT framework, which is an abbreviation for six parameters of Groundwater occurrence, Aquifer hydraulic conductivity, Level of groundwater above sea level, Distance from the shoreline, Impact of the existing status of seawater intrusion, and Thickness of the aquifer, is a well-known framework for evaluating the groundwater vulnerability in coastal zones. In this study, two meta-heuristic algorithms of Grey Wolf Optimizer (GWO) and Genetic Algorithm (GA) were proposed to optimize the weights of GALDIT framework. This framework was tested in the Gharesoo-Gorgan Rood coastal aquifer located in the north of Iran. The GALDIT index illustrated poor evaluation of vulnerability to seawater intrusion. Contrariwise, GALDIT-GWO and GALDIT-GA frameworks provided results that are more reasonable. Both vulnerability maps showed a close similarity in terms of vulnerability to seawater intrusion. The vulnerability maps demonstrated that the west and northwest parts of the study area suffer from seawater intrusion. Additionally, the values of Spearman’s rank correlation coefficient between the indices of GALDIT, GALDIT-GWO and GALDIT-GA and the parameter of Cl/HCO3 were obtained as 0.31, 0.53, and 0.49 and the corresponding values for the parameter of TDS were obtained 0.45, 0.64 and 0.60, respectively. Therefore, it can be concluded that the proposed optimization models are able to provide accurate results. Furthermore, these models reduce the subjectivity and increase the capability of the GALDIT index.

Groundwater Aquifer Vulnerability Assessment using a Dar-Zarrouk Parameter in a Proposed Aboru Residential Estate, Lagos State, Nigeria

The need to build an automobile mechanic settlement, abattoir and a proposed meat processing factory at Aboru residential estate necessitated a geophysical assessment (using a Dar-Zarrouk parameter – longitudinal unit conductance, S) of the vulnerability of the subsurface aquifers in the study area against the expected long-term anthropogenic impacts of these facilities on the groundwater system. Thirteen (13) Vertical Electrical Sounding (VES) points and four (4) Dipole-Dipole resistivity profile lines were occupied on four traverse lines across the study area. Isoresistivity and Isopach maps were generated and Total Longitudinal Unit Conductance, S of the earth materials overlying the aquifer was computed and the aquifer protective capacity (APC) map was generated. The VES delineated four (4) geo-electric layers namely; topsoil, pebbly/lateritic sand, clay/clayey/silty sand and sandstone. The depth to the sandstone aquifer ranges from 30.6 – 39.4 m with resistivity values ranging from 851 – 1437 Ωm. The iso-resistivity and isopach maps reveal that the near surface lateritic materials with resistivity values ranging from 350 – 1150 Ωm and thicknesses ranging from 2 – 29 m are pervious. The Total Longitudinal Unit Conductance, S varies from 0.0164 - 0.1168 mhos indicating a poor to weak protective capacity rating across the study area and the APC map reveals that the north-eastern and western parts of the study area show areas with weak protective capacity ratings while other areas are characterized by poor protective capacity rating. As such, the establishment of the proposed service facilities in the study area is strongly discouraged as the nature of their operations has a high potential to contaminate and eventually pollute the sub-surface aquifers on the long-run. If however the inevitability of their establishment cannot be set-aside, then secondary measures must be taken to forestall a direct impact of their operations on the subsurface. Keywords : Aquifer, Dar-Zarrouk, Vulnerability, Longitudinal Unit Conductance

Transboundary groundwater resource management: needs for monitoring the Cijevna River Basin (Montenegro–Albania)

The transboundary Cijevna River Basin shared between Albania and Montenegro has a surface area of 650 km2. It is extremely important for water management, especially in the country of Montenegro which is downstream. Due to the high permeability of both the karst and intergranular aquifers that exist in the basin, the River Cijevna sinks along the length of its riverbed and in summer months it usually dries up completely at the confluence section. Hydrometry surveys undertaken during a drought period have identified the most permeable zones along the river, while the loss between sections varies between 0.137 and 0.765 m3/s/km’. An aquifer vulnerability assessment has been conducted through the implementation of both the EPIK and DRASTIC methods. Identifying both the most permeable and vulnerable zones in the basin assisted in the initial design of a joint Groundwater Monitoring Network for the two countries. It should consist of 21 observation points, automatic hydrology stations on the river and selected springs, and data loggers within installed piezometers. Once completed with remote data transmission and the implementation of a real-time data-sharing mechanism, it will be the first of its kind in “classical” Dinaric karst region, and one of very first to exist within karst aquifers anywhere.

A New Approach for Aquifer Vulnerability Assessment: the Case Study of Campania Plain

We are going to propose a new method for aquifer vulnerability assessment, named Susceptibility Index-Contamination Degree (SICODE). Starting from the assumption that soil chemistry impacts on infiltration water quality, geochemical tool such as the soil contamination degree index (CD) was combined with hydrogeological parameters in order to enhance previous well-known index (DRASTIC, Susceptibility Index). The study has been carried out at the Campania Plain (CP) aquifer, which mostly supplies the drinking water distribution system of Napoli (Southern Italy). The survey area extends from Mt. Vesuvius to the metropolitan area of Napoli and it can be considered an interesting field laboratory in order to test hydro-geochemical methods and models since both diffuse anthropogenic pollution and natural contamination sources (e.g. interaction processes between groundwater and rock) coexist. Three models have been compared. Our results have showed that DRASTIC is not the best model to be applied to urbanized environments since it does not account for the anthropogenic influence. Susceptibility Index (SI), which incorporates land use parameter, has showed a more detailed map of vulnerability degree and it better answers the local variability of human pressure. However, the proposed SICODE method completely meets the geochemical fingerprint of soil. Sensitivity analysis has revealed a high variability of the parameters due to the local heterogeneity of the analyzed system conditions. A comparison between the groundwater nitrates distribution and the predicted vulnerability has showed that. SICODE gave more accurate predictions than the other ones. This study has provided the evidence that combining hydrogeological and geochemical tools may enhance aquifer vulnerability assessment.

Assessment of Aquifer Vulnerability Using Integrated Geophysical Approach in Weathered Terrains of South China

Abstract Despite being rich in groundwater resources, assessment of hard-rock aquifers in many areas of Asia is difficult given their strong heterogeneity. However, delineation of such aquifers is essential for estimation of the groundwater reserves. In addition, the vulnerability of hard-rock aquifers is controlled by the weathered/fractured zones because it is the place where most of the groundwater reserves are contained. In this work, an integrated approach of the electrical resistivity tomography (ERT), high precision magnetic, X-ray Diffraction (XRD), physicochemical analysis and pumping test data was performed to investigate the hard-rock aquifers occurring in the weathered terrains. This approach reveals seven fractures/faults (F1 to F7) and four discrete layers such as the topsoil cover, highly weathered, partly weathered and unweathered rock. The groundwater resources are estimated as a function of different parameters i.e., aquifer resistivity (ρo), transverse unit resistance (Tr), hydraulic conductivity (K), transmissivity (T), rock formation factor (F) and rock porosity (Φ). These parameters divide the groundwater resources into four aquifer potential zones with specific ranges of ρo, Tr, K, T, F and Φ i.e., high, medium, poor, and negligible potential aquifers. The results suggest that the high potential aquifer reserves are contained within the weathered/fractured and fault zones. The X-ray diffraction (XRD) technique analyzes quartz as the major mineral (>50%). The physicochemical and geophysical analysis suggests good groundwater quality in the investigated area. The integrated results are highly satisfied with the available borehole information. This integrated geophysical approach for the estimation of groundwater resources is not only applicable in the weathered terrains of South China, but also in many other areas of the weathered/fractured aquifer in Asia and beyond.

Integrated environmental modeling for efficient aquifer vulnerability assessment using machine learning

Nitrate contamination in groundwater was evaluated using the concept of integrated aquifer assessment by combining groundwater characterization and risk analysis with tiered approaches for land and surface runoff contamination by soil chemicals and leaching of contamination to groundwater in the Upper White River Watershed (UWRW) in Indiana. Integrated aquifer vulnerability assessment was conducted using an integration of a distributed watershed model (Soil and Water Assessment Tool [SWAT]) and a machine learning technique (Geospatial-Artificial Neural Network [Geo-ANN]). The results indicate that integrated aquifer vulnerability assessment performed well based on the model performance (NSE/R2/PBIAS = 0.66/0.70/0.07). Thus, the overall assessment of aquifer vulnerability can be performed using the integrated aquifer vulnerability assessment technique provided in this study. Moreover, this approach provides an efficient guide for managing groundwater resources for policy makers and groundwater-related researchers.

Geophysical assessment of aquifer vulnerability and management: a case study of University of Nigeria, Nsukka, Enugu State

Seventeen vertical electrical soundings and seven electrical resistivity tomography profiles were carried out at the University of Nigeria, Nsukka, Enugu State, Nigeria. The study involves the use of Schlumberger and Wenner electrodes configuration. The thrust of this work is on determining the vulnerability of the hydrogeological units by employing the aquifer vulnerability index (AVI) method. The resistivity data measured were interpreted manually and with computer software packages, which gave the resistivity, depth and thickness for each layer within the maximum current electrodes separation. The hydraulic conductivity (K) and hydraulic resistance (C) of the protective layers estimated from the primary parameters estimated have values ranging from 0.0434 to 0.4890 m day−1 and 38.37 to 1005.84 day−1, respectively. AVI of the study shows that the study area is characterised by low to high AVI with moderate AVI as dominant. This is to help in delineating aquifer protective zones and also possible locations, which further helps in groundwater resource exploration and management.