Groundwater Vulnerability Assessment Research Articles

Assessment of groundwater vulnerability using water quality index and solute transport model in Poiney sub-basin of south India.

This paper demarcated the most vulnerable regions within the Poiney sub-basin (Tamil Nadu state in India) with respect to the groundwater quality. An index-based vulnerability assessment was carried out by measuring the physico-chemical variables such as pH, electrical conductivity, total dissolved solids, magnesium, sodium, chloride, sulphate, bicarbonate and fluoride in the pre-monsoon and post-monsoon samples. Water quality index varied across the sub-basin due to differences in the water quality induced by anthropogenic activities related to land use practices and presence of industries. The MT3D engine coupled with visual MODFLOW identified that sulphate released from tanneries and leather factories is the main effluent contaminating the groundwater. Model reveals that both the flow and contaminant transport is towards southeast with maximum and minimum calculated head of 201.82mg/l and 265.92mg/l and calculated sulphate concentration of 394.40mg/l and 46.79mg/l respectively.

Groundwater vulnerability assessment using AHP-DRASTIC-GALDIT comprehensive model: a case study of Binhai New Area, Tianjin, China.

Binhai New Area (BHNA), as one of the most economically and industrially regions in the Haihe River Basin, China, is seriously affected by seawater intrusion and groundwater over-exploitation. Groundwater vulnerability assessment (GVA) is an effective tool to protect the groundwater resources from being polluted. In this study, vertical and horizontal groundwater conditional factors were first assessed separately by two different models. The AHP-DRASTIC model was used to evaluate the intrinsic groundwater vulnerability and the AHP-GALDIT model was used to evaluate the specific groundwater vulnerability to seawater intrusion. Then, a GIS-based overlaying approach was used to get the comprehensive shallow groundwater vulnerability. The results of the comprehensive model showed that the vulnerability areas of very low, low, medium, and high account for 1.37%, 11.36%, 60.56%, and 26.71%, respectively. Finally, to effectively manage the groundwater in the study area, two remediation areas, two control areas, and one protected area were determined based on the comprehensive groundwater vulnerability maps. This study can not only promote the development of rational exploitation of shallow groundwater and prevention of groundwater pollution in BHNA but also provide a framework for future research in the GVA on the coast.

Stochastic-based approach to quantify the uncertainty of groundwater vulnerability

The study proposes a stochastic approach to quantify the uncertainty of groundwater vulnerability (GV) produced by classical index-overlay methods. In the analysis, the physical-based MODFLOW model has been integrated with the DRASTIC method and modified by the analytical hierarchy process (AHP) technique. Specifically, the flow fields from the MODFLOW model provide the parameters of depth to water and the associated hydraulic conductivity (K) for the DRASTIC method. The integrated loops between the MODFLOW and DRASTIC models enable the evaluations of GV maps by considering sources of uncertainty in geological parameters and stress changes in an aquifer system. In illustrating the approach for practical implementations, the study considers the uncertainty produced by the heterogeneity of K in the Pingtung Plain groundwater basin in southern Taiwan. Different degrees of K heterogeneity were assessed to quantify the impact of the K heterogeneity on the GV mappings. Results show that the integration of parameter uncertainty information from the stochastic-based approach for GV mapping can improve the accuracy and reliability of the GV assessment. The stochastic GV maps have accounted for the source of the K uncertainty. There are significant discrepancies in GV values in the spatial distribution and intensity in all GV classes. The results clarify the potential risk of groundwater contamination in the Pingtung Plain groundwater basin.

Assessment of Groundwater Vulnerability using GOD Method

Assessment of Groundwater Vulnerability using GOD Method

Groundwater vulnerability assessment using GIS modeling for north-east area of Tadla plain (Morocco)

Groundwater vulnerability assessment using GIS modeling for north-east area of Tadla plain (Morocco)

Assessment of Ground Water Vulnerability to Pollution in the City of Bafoussam, Western Region-Cameroon

This work consisted in evaluating the vulnerability of groundwater to pollutants coming from the surface. This evaluation is done using the parametric method of SINTACS based on seven physiographic and hydrogeological parameters obtained from remote sensing data (DTM) and exogenous data (lithological, soil, rainfall, hydrogeological). The results obtained reflect the risk of pollution of water resources by various sources (urban, industrial and agricultural). Particularly in agricultural areas responsible for water pollution by nitrates and in urban centers where water pollution by faecal contamination is felt. A mapping of intrinsic vulnerability and specific vulnerability reveals with regard to specific vulnerability to faecal pollution with E-coli as a bio-indicator, that 51.78% of the area has an average specific vulnerability to faecal pollution, 30.24% a low vulnerability and 17.99% has a very low character to faecal pollution. Regarding agricultural pollution, the chemical indicator used is nitrate. The analyzes show that 8.37% of the area has a high specific vulnerability to agricultural pollution, 12.37% an average vulnerability and the rest a low or very low vulnerability.

Using COP Model to Map the Vulnerability of Groundwater Wells Adjacent to Landfills

Protecting the quality of the groundwater is of the utmost importance, particularly in countries such as Jordan, where the groundwater comprises a significant portion of the total water resources. A groundwater vulnerability assessment is one of the viable preventive measures that is normally used to preserve this strategic water resource. Groundwater vulnerability maps provide information on the groundwater basins that are vulnerable to contamination, particularly those coming from the landfills, and thus, they can be used for sustainable land use planning. The general goal of this study was to map the groundwater vulnerability to contamination and evaluate the impact of landfills on the groundwater quality at five landfill sites in Jordan, i.e., Akaider, Al-Husaineyat, Madaba, Dair Alla, and Azraq by using a COP hydrogeological model. The COP method is an European approach for aquifer vulnerability in the karst regions. This method uses the parameters: C—Concentration of flow; O—Overlying layers; P—Precipitation. Unlike the other methods, the COP model allows for us to assess the impact of the karst systems if they exist. For the study area, daily rain records from three weather stations surrounding each landfill were used. Along with the vulnerability maps, Peizometric maps for Akaider, Azraq, Dair Alla, Madaba and Al-Husaineyat were produced that assisted in our efforts to determine the wells located in the upstream and downstream of each targeted landfill. The water quality was tested two times in the upstream and downstream wells of each targeted landfill to explore the potential impacts of the landfills on the groundwater wells. The developed vulnerability maps show that most of the lands surrounding the landfills’ areas, within a diameter of 15 km, are located in low to very low vulnerability areas, except for the Al-Husaineyat landfill in Mafraq where a significant part of it lies in a moderate vulnerability area across a fault section. Additionally, the results of the water analysis from the surrounding wells indicated that there was no clear evidence of the contamination of the groundwater resulting from surrounding landfills, which was in agreement with the produced vulnerability maps.

Comparison of GIS-Based Intrinsic Groundwater Vulnerability Assessment Methods: DRASTIC and SINTACS

The possibility of contaminants percolating and diffusing into the groundwater system is referred to as groundwater vulnerability. When groundwater once gets polluted it is very difficult to process/clean it so, measures must be taken to assess the vulnerability of the groundwater for effective groundwater conservation and management planning. This study aims to evaluate and map the vulnerability of Raipur city using the SINTACS and DRASTIC models and to compare their effectiveness between them. To assess the hydrogeological setting and evaluate aquifer vulnerability, each model includes seven environmental parameters (aquifer hydrogeologic features, effective infiltration, topographic slope, soil media, water table depth, unsaturated conditions, and hydraulic conductivity). The parameter data sets are evaluated in a Geographical Information system (GIS) environment to get the vulnerability index (VI), the index is categorized into five classes that show low to high vulnerability. The area under the low class for DRASTIC and SINTACS is 26.14% and 20.34% respectively whereas for the highly vulnerable class it is 15.54% and 22.54% respectively of the total area. By comparing the 15-groundwater sample value of nitrate concentration on the two vulnerability maps it was found that the SINTACS method result was shown to be significantly associated with the nitrate concentration with an accuracy of 86.7 percent.

A semi-automatic approach for doline mapping in Brazilian covered karst: the way forward to vulnerability assessment

Doline mapping is paramount in the vulnerability and risk assessment of the underground karst environment by identifying cave-ground connectivity points at the surface. However, manual mapping is labour-intensive, slow and subjective, especially on a large scale. Therefore, the present study adopted a GIS-based semi-automatic approach for mapping large and medium-sized depressions/dolines in the Corrente river basin in Brazil, with a particular focus on the environmentally preserved areas of river Vermelho (APANRV Portuguese abbreviation) using remote sensing (DEM and Google Earth imagery) and field-based observations. Seven typical dolines forms (e.g., cockpit with drain insertion, collapse, collapse with river capture, suffosion, solution, cover collapse, and buried) are found from extensive field surveys. As an outcome of the proposed approach, two hundred and thirty-two medium to large-sized dolines have been identified and categorised into three main groups based on the cave density and local geology G1, G2, and G3. The high density of identified dolines (164 known caves) in G1 provides reconnaissance for future speleological works in the preserved areas. Additionally, the presence of a considerable number of dolines in the adjoining areas (G2 and G3) stresses the need to revise the existing boundaries of the APANRV. Results correlate well with the dolines sites marked using field surveys and Google Earth images. This doline mapping may help researchers in the groundwater vulnerability assessment and the protection of speleological heritage preserved in the caves.

Evaluation of Arid Soil Landscapes Permeability in Algerian Sahara

The hydro-edaphic environment of arid ecosystems in Ouargla is endangered. To the sustainability of this fragile ecosystem, detailed knowledge of geomorphology, surface characteristics, vegetation, and hydrodynamic characteristics of the soil is required. Soil permeability is an important hydrodynamic parameter for the assessment of infiltration, structure design, drainage, and groundwater vulnerability, but it has not been studied in Ouargla. In order to ensure better management of the irrigation-drainage and to better characterize the variability of the water dynamics in the soils of this region, we have measured the permeability of these soils by Porchet’s method, taking into consideration the pedo-landscapes of the region: Plateau, Glacis, Erg, Reg, and Sabkha. Soils of Ouargla are semi-permeable with 4.58 m/d, which gives them good drainage capacity and facilitates the transfer of pollutants to groundwater. A difference in the mean permeability of the soils from one pedo-landscape to another is noticed, but only the difference in mean between the soils of Erg and those of Glacis is statistically significant according to the ANOVA and Tukey test.

Incorporating remote sensing techniques to the DRASTIC index to assess groundwater vulnerability at mining areas: application to Sonora river aquifer, northwestern Mexico

Groundwater metal pollution is a major concern in mining areas. This study proposes a new addition to the DRASTIC method (DRASTIC+Lu) to assess groundwater vulnerability to metal pollution in mining areas by combining remote sensing (to locate metal pollution sources) and the DRASTIC index. The study was performed in a mining area in northwestern Mexico showing current and historical mining activities. The proposed methodology allowed locating known and unknown sources of metal pollution (mining tailings, active/inactive mines, and areas with exposed natural geochemical anomalies). Generally, the addition of the land use (Lu) parameter causes not only a decrease in vulnerability but also highlights very high vulnerable areas and identifies new ones in the vicinity of metal pollution sources. This result is relevant to focus stewardship efforts in very high vulnerable areas. Results allowed to identify the need to implement protection and restauration measures in the Sonora river channel and its vicinity. The proposed method could be implemented in other mining areas around the world –at a low cost– to locate unknown metal pollution sources and clearly identify very high vulnerable areas that play a key role in the protection of groundwater resources.

GIS-based assessment of selective heavy metals and stable carbon isotopes in groundwater of Islamabad and Rawalpindi, Pakistan

This study applied a nuclear technique in conjunction with a classical monitoring tool to characterize the origin, fate, and behavior of metal pollutants in groundwater of Islamabad-Rawalpindi Metropolitans, which are also known as the “twin cities.” In total, 122 groundwater samples were collected and analyzed in accordance with standard methods. GIS and multivariate statistical analysis were employed for the groundwater vulnerability assessment and source apportionment. The results of the aesthetic parameters indicated that the majority of groundwater sources were tested and were colorless, odorless and tasteless in the “twin cities.” In addition, the findings of this study indicated that the concentration of pH, phosphates, copper, manganese, and zinc were within the drinking water standards in the “twin cities” as stipulated by the World Health Organization (WHO) and Pakistan Standard and Quality Control Authority (PSQCA) at all sampling points in the study area. The groundwater quality was found unsuitable for consumption due to elevated levels of electrical conductivity and total dissolved solids at 9.83% and 4.09% of samples, respectively. The contents of arsenic and fluoride were well within the allowable range at almost all points except at one location. However, iron and lead contents were above permissible limits. A statistical analysis revealed that trace metals originated from both geogenic and anthropogenic sources such as enhanced rock-water interaction, over abstraction, evaporation enrichment, improper waste disposal, discarded batteries, cross contamination of water supply and sewerage lines, active recharge from Lie drain, and domestic, industrial, and agricultural effluents. The computed water quality index (WQI) based on heavy metals elucidated that groundwater quality was poor in most of the study area due to elevated electrical conductivity, total dissolved solids, lead, iron, arsenic, and fluoride values. A highly depleted isotopic composition of 13C provides clues about the aquifer’s vulnerability from miscellaneous sources such as domestic, urban, construction, and agricultural sites and the dissolution of carbonate minerals. This study clearly indicates that a rapidly growing population, unplanned urbanization, industrialization, improper waste disposal, over abstraction, and a lack of water abstraction policies are significantly contributing toward the impairment of groundwater quality in the study area. The study strongly emphasized the need to regulate groundwater abstraction by improving water treatment and the supply system for the provision of safe water to the urban populace. These results will help in designing remedial strategies for improving water quality in the “twin cities.”

Geohydraulic characteristics and groundwater vulnerability assessment of tropically weathered and fractured gneissic aquifers using combined georesistivity and geostatistical methods

Sustainable groundwater yield in aquifers depends on the protective capacity of the subsurface lithologies and conduit systems. Electrical resistivity tomography (ERT) and its Schlumberger vertical electrical sounding (VES) technique were employed to assess the groundwater yield of aquifer units and their vulnerability to contaminants in Araromi (Akungba-Akoko), southwestern Nigeria. Geohydraulic parameters: aquifer resistivity (\rho0), hydraulic conductivity (K), transmissivity (T), permeability (\Psi), hydraulic resistance (KR), and longitudinal conductance (S) were also evaluated. In addition, regression analysis was utilized to establish the empirical relationships between the K and other geohydraulic parameters, with their percentage contributions to posing vulnerability risk. The georesistivity results revealed four distinct layers: topsoil, weathered layer, partially weathered/fractured bedrock unit, and fresh bedrock. The K model regression-assisted analysis showed that the \rho, T, \Psi, and S contributed about 97.8%, 14%, 99.9%, and 11.5%, respectively, to the estimated aquifers’ K values for the study area. Except for T and S, the regression results had moderate to strong positive correlations with K; hence, this illuminates the essentiality of K in assessing groundwater potential and vulnerability. The aquifer units have low to moderate groundwater yield based on T values (1.67-17.57 m/day) caused by the generally thin overburden (<4 m). However, the deep-weathered and fractured aquifer units with depths ranging from 39-55 m could supply high groundwater yield for sustainable abstraction. The estimated S values (0.0226-0.1926 mhos) for aquifer protective capacity ratings rated the aquifer units in the area as poor to weak. Based on the estimated low logarithm of KR (log KR) values of 0.79-2.25 years, these aquifers have extremely high to moderate aquifer vulnerability index. As a result, prospective wells/boreholes in the study area and settings with similar geohydraulic and vulnerability characteristics should be developed adequately to prevent the infiltration of surface contaminants for potable groundwater abstraction.

A Modified GALDIT Method to Assess Groundwater Vulnerability to Salinization—Application to Rhodope Coastal Aquifer (North Greece)

Aquifer overexploitation in coastal aquifers has led to seawater intrusion that causes severe salinization effects on the groundwater system. The most widespread method for assessing groundwater vulnerability to seawater intrusion, the dominant cause of salinization in coastal aquifers, is the GALDIT method, with numerous applications globally. The present study proposes a modified version of the GALDIT method (GALDIT-Ι) to evaluate the vulnerability of salinization, including its potential additional sources. Both methods have been applied to Rhodope coastal aquifer, an intensively cultivated agricultural area subject to multiple salinization sources. The basic modifications of the proposed GALDIT-I method include different weighting factors and modification of classes for critical parameters, the use of a different indicator (TDS) for the estimation of the Impact factor and, overall, the address of the concept of groundwater salinization instead of seawater intrusion only. The differences in the results of the two methods were significant, as the modified version exhibited a more finite and realistic vulnerability capture, according to the area’s existing hydrogeological and hydrogeochemical knowledge. The original GALDIT method showed an area of nearly 80% as medium vulnerable with very limited spatial deviations. On the other hand, the proposed modified GALDIT method depicted high vulnerability hotspots away from the shoreline, indicating various salinity sources. The validation of the modified method showed that nearly 80% of the sampling points present very good to perfect match between the salinity assessment and the concentration of Cl−, indicating the successful validation of the method. Overall, the GALDIT-I method facilitated groundwater vulnerability assessment to salinization more accurately and exhibited a more discrete spatial assessment, thus, it could be regarded as a promising proactive tool for groundwater management and decision-making.

The Use of the DRASTIC-LU/LC Model for Assessing Groundwater Vulnerability to Nitrate Contamination in Morogoro Municipality, Tanzania

Groundwater is a useful source of water for various uses in different places. The major challenge in the use of this resource is how to manage and protect it from contamination. The current study was conducted in Morogoro Municipality to identify vulnerable groundwater areas by using DRASTIC-LU/LC model. The study applied eight input parameters, i.e., depth to water table, net recharge, aquifer media, soil media, topography, impact of vadose zone, hydraulic conductivity and land use/land cover patterns, which were overlaid in GIS to generate groundwater vulnerable map. The model used rating (R = 1–10) and weighting (W = 1–5) techniques to assess the effect of each parameter on groundwater contamination. The DRASTIC-LU/LC Vulnerability Index map was classified into low- (area = 29.2 km2), moderate- (area = 120.4 km2) and high-vulnerability zones (area = 124.4 km2). Nitrate analysis was conducted using the cadmium reduction method (DR 890) to assess the validity of the model and it was observed that 55%, 15% and 50% of the samples with unacceptable (>50 mg/L), high (29–50 mg/L) and moderate (14–28 mg/L) nitrate concentrations, respectively, fall into the high-vulnerability zone. Furthermore, 45%, 70% and 50% of the samples with unacceptable, high and moderate nitrate concentrations, respectively, fall into the moderate-vulnerability zone. In the low-vulnerability zone, only 15% of samples were found with a high nitrate concentration.

Comparison of DRASTIC and DRASTICL groundwater vulnerability assessments of the Burdekin Basin, Queensland, Australia

In the Burdekin Basin, Queensland, Australia, groundwater contamination due to agricultural activities has led to concerns over its impacts on globally significant ecosystems such as the Great Barrier Reef. An appropriate method for groundwater vulnerability assessment is essential for the sustainable use of this groundwater resource and its longer-term environmental management. The aim of this study is to apply and assess the suitability of the standard DRASTIC index-based method for groundwater vulnerability assessment of the Burdekin Basin. The intrinsic groundwater vulnerability is calculated in ArcGIS, using data for the period 2010 to 2021. The results are compared to available water quality data. The calculated DRASTIC scores are found to be only weakly correlated with water quality parameters, including the nitrate concentration (R = 0.07), which should behave as a proxy measure of groundwater vulnerability. To address this, a modified DRASTICL method containing a land use parameter is also implemented, to assess the specific groundwater vulnerability. The correlation between DRASTICL scores and nitrate levels (R = 0.2) is more significant but is still relatively weak. From this study, it is recommended that alternative methods be developed to assess groundwater vulnerability in the Burdekin Basin, and other comparable aquifer systems.

Comparative assessment of groundwater vulnerability using GIS-based DRASTIC and DRASTIC-AHP for Thoothukudi District, Tamil Nadu India.

The groundwater is very precious in the world. Rapid urbanization and industrialization create tremendous stress on groundwater quality and quantity. Unscientific groundwater extraction and waste disposal methods impact the groundwater aquifer's susceptibility in the coastal area. This research examines how industrial waste, seawater intrusion, and solid waste dumping affect the Thoothukudi District, located on the southwest coast of Tamil Nadu, India. The groundwater vulnerability potential is determined using the DRASTIC and analytical hierarchy process (AHP)-based DRASTIC model. DRASTIC-AHP method's weights and ranks are determined using multi-criteria decision analysis (MCDA)-based pairwise comparison method. Remote sensing (RS) and geographical information system (GIS) are implemented to prepare the input layers for DRASTIC and DRASTIC-AHP. The findings reveal a very high category of vulnerability along the coastline that is covered in sand and loose sediments from an aquifer. Similar conditions exist on the southeast side, which is covered with gravel, sand, and sandstone with shale and has relatively low-slope topography. This enables higher contaminant percolation into the groundwater and raises the possibility for pollution. The DRASTIC-AHP method's results reveal that the southeast side has a significant possibility of contamination. The water table, net recharge, vadose zone, and conductivity greatly impacted the DRASTIC vulnerability assessment due to their stronger weight than theoretical weight. It may be stated that the DRASTIC technique is more cost-effective and time-efficient in analyzing a wide range of regional groundwater risks while avoiding sloppy, uncontrolled land development and other unwanted activities.

Assessment of Groundwater Vulnerability to Contamination using GIS-based DRASTIC model in Lucknow, India

Abstract: Groundwater intrinsic vulnerability maps are considered a promising means for forestalling groundwater resources from contamination in recent years. With the use of a Geographic Information System (GIS) and hydro-geochemical data, the DRASTIC model is used to forecast groundwater vulnerability. For which ArcGIS software is used. Lucknow, capital of Uttar Pradesh, is the study area for this study. This model is based on the seven data layers that provide the input to the modelling. It corresponds to the initials of seven layers i.e. Depth to water, net Recharge, Aquifer media, Soil media, Topography, Impact of vadose zone ,and Hydraulic Conductivity. Mal and Sarojani Nagar Block showed higher vulnerability (139–143). The results also suggested that the low, moderate, and high groundwater vulnerability zones cover around 30.35%, 45.02%, and 24.63 % of the study area, respectively. The results is validated using nitrate concentration in groundwater. The percentage of study area for nitrate concentrations <45 mg/l, 45-60 mg/l, 60-80 mg/l, and 80-110 mg/l are 55.5%, 34.5%, 9%, and ~1% respectively. The GIS technique has provided an efficient tool for assessing and analysing the vulnerability to groundwater pollution.

Groundwater Vulnerability of Halabja-Khurmal Sub-Basin Using Modified DRASTIC Method

Evolving groundwater vulnerability from DRASTIC to modified DRASTIC methods helps choose the most accurate areas that are most delicate toward pollution. This study aims to modify DRASTIC with land use and water quality index for groundwater vulnerability assessment in the Halabja-Khurmal sub-basin, NE/Iraq. The Halabja-Khurmal sub-basin groundwater vulnerability index is calculated from nine hydrogeological parameters by the overlay weighting method. As a result, 1.3% of the total area has a very high vulnerability value and 46.1% with high vulnerability. The regions with high groundwater vulnerability have a high-water table and groundwater recharge. Nitrate concentration was used to validate the result, and the Pearson correlation and recession analysis between the modified DRASTIC index and nitrate concentration depicted a strong relation with 0.76 and 0.7, respectively.

Vulnerability methods in hard rock formation as a basis for groundwater risk assessment – from resource to source

Groundwater in a hard rock formation is most endangered at places where a potential source can discharge contaminants that can reach the saturated zone of an aquifer. In these circumstances, an essential tool for groundwater protection is the contamination risk map. This map is based on the integration of two maps: a hazards map, i.e., map of potential sources of contamination and a vulnerability map. The selection of a proper vulnerability method is an important task since the resulting vulnerability map can significantly impact the final risk of contamination map. The most appropriate method for groundwater vulnerability assessment was considered in the case study of Tara National park, in Western Serbia. The four commonly used methods were applied to assess the intrinsic vulnerability maps: DRASTIC, EPIK, PI and COP. All the applied methods resulted in different vulnerability maps in assessing the degree of vulnerability, consequently influencing the groundwater contamination risk maps. The applied research presents an example of how contamination risk should be assessed in a specific area. Comparison of the results obtained for the area of Tara National Park indicates the preference of the PI method as a well-balanced method, taking into account all the specifics of the study area. A detailed analysis of the assessed risks in the catchments of the existing sources was also conducted to indicate probable sources of contamination and confirm the degree of accuracy of the created vulnerability and risk maps. The conducted research emphasizes the necessity to adopt a clear conceptual hydrogeological model and to apply several methods simultaneously to determine the optimal one for each individual area.