High Groundwater Vulnerability Research Articles

Utilizing Geological and Geoelectrical methods in a GIS-based DRASTIC model of the Probable Groundwater Vulnerability in the Southern Nigerian Raffia Metropolis of Ikot Ekpene and its Surroundings

The city of Ikot Ekpene is facing a significant issue with groundwater contamination. This is due to the rising amount of home and industrial waste caused by the increasing human population and various business operations in the area. This study seeks to evaluate the susceptibility of groundwater in the metropolis of Ikot Ekpene and its surrounding areas in southern Nigeria. It will utilize integrated geoelectrical and geological approaches within the GIS-based DRASTIC model. A total of twenty vertical electrical soundings (VES) were conducted in the region using the Schlumberger array. Based on the geological drilling data, the interpretation of the VES data suggests that the area consists of 3-4 geoelectric layers. The lithological succession in the area exhibits a range of sediment types, including fine and coarse sand as well as gravelly sands. Additionally, there are localized occurrences of clay intercalations. The third geoelectric layer, located at a depth of 9.0–86.6 m, is the primary aquifer that can be utilized in the region. The DRASTIC model included seven environmental parameters, including depth to the water table, net recharge, aquifer medium, topography, impact of vadose zone, and hydraulic conductivity, with the purpose of conducting a vulnerability assessment. The assessment of groundwater vulnerability ratings (GVR) reveals that 75% of the research region is classified as high vulnerability, 20% as moderate vulnerability, and the remaining 5% as low vulnerability. The studied area is predominantly characterized by moderate to high Groundwater Vulnerability Rating (GVR), which is likely attributed to the generally gentle topography and the presence of highly permeable geomaterials in the upper levels of the water table.

A comparison of methods for assessing groundwater vulnerability in karst aquifers: the case study of Terminio Mt. aquifer (Southern Italy)

The assessment of groundwater vulnerability to pollution is becoming even more important all over the world due to the increase of impacts of human activities on groundwater resources and the related risks to the human health, economics, and the environment. Owing to the variability of methods known for estimating groundwater vulnerability, basically depending on hydrogeological parameters considered and the scale of analysis, the comparison of results of different methods appears straightforward for identifying the best approach in a given hydrogeological condition and reference scale. In such a view, this work attempts to assess the groundwater vulnerability of the Terminio Mt. karst aquifer, by applying four different groundwater vulnerability methods, index-based, and comparing results in order to identify the best performing one in karst environments. The study aquifer, located in the Picentini Mts Regional Park (Campania region, southern Italy) represents a strategic drinking water resource since Roman times and hosts massive groundwater resources which outflow mainly from tapped basal and subordinately perched springs.The peculiar characters of the study karst aquifer, which favour direct infiltration and groundwater recharge processes, as well as the occurrence of industrial, agricultural and grazing activities, make it very vulnerable to groundwater pollution, thus requiring a proper and careful territorial management.Beside the most frequently and generally used methods for assessing groundwater vulnerability, such as the DRASTIC and SINTACS, also DAC and COP methods specifically designed for karst aquifers were applied and mutually compared. Results of SINTACS, DRASTIC and DAC methods show groundwater vulnerability maps of the Terminio Mt. karst aquifer as chiefly characterized by two classes of intrinsic groundwater vulnerability, varying between the medium and high degrees. Furthermore, high and extremely high values of groundwater vulnerability were found in areas controlled by the shallow depth of the water-table. Instead, the COP method resulted as the most effective in identifying the endorheic areas and the related karst morphologies as very high groundwater vulnerability zones, therefore the most suitable in capturing specific hydrogeological features of karst areas that control groundwater pollution and vulnerability.Results obtained will support decision tools aimed at the land use planning and protection of karst aquifers from pollution in karst areas.

Vulnerability and Risk of Contamination of the Varaždin Aquifer System, NW Croatia

This paper presents the first study that assesses the vulnerability and risk of contamination of groundwater in the Varaždin aquifer system. The alluvial aquifer system is mostly unconfined with favorable hydrogeological features. Out of three wellfields, two still operate at full capacity, while the Varaždin wellfield, once the major source of drinking water, has been abandoned due to high concentrations of nitrates in the groundwater. Index-based methods are employed to assess groundwater vulnerability—two DRASTIC-based methods, standard and P-DRASTIC; two SINTACS-based methods, with normal and severe weighting strings; and the GOD method. Hazard is evaluated according to recommendations from the EU COST 620 action, while the risk intensity of the resource is calculated using the results of vulnerability and hazard assessments. The results reveal that for all vulnerability models, the resulting maps have a similar distribution pattern of vulnerability classes, with the high vulnerability class prevailing. However, notwithstanding the generally high groundwater vulnerability, a moderate resource contamination risk prevails as a consequence of a dominantly low hazard index. The validation of the groundwater vulnerability models demonstrates a weak correlation between the vulnerability indices and mean nitrate concentrations in groundwater. Conversely, a significantly higher correlation coefficient (0.58) is obtained when the groundwater vulnerability index is replaced by the resource risk intensity index, indicating that the results of resource risk intensity assessments are superior to groundwater vulnerability results in predicting the level of groundwater contamination.

Groundwater vulnerability assessment of nitrate pollution in the Ankang Basin: using an optimized DRASTIC-LY method.

This study retains the basic structure of DRASTIC model and obtains more specific evaluation results by adding land-use type and groundwater resource yield parameters, modifying the rating scale and weight of nine parameters. Comparison of the modified DRASTIC-LY vulnerability map with the map of the original DRASTIC-LY method revealed differences in 40.49% of the study area. The risk map shows that the very high vulnerability area decreased from 2.79 to 1.67%, while the high vulnerability area increased from 18.70 to 28.86%. Areas with low vulnerability increased by 10.15%, while areas with medium vulnerability decreased by 15.01%. The areas with very high groundwater vulnerability are mainly distributed in the Hanbin area on the north bank of the Han River, the areas with high are mainly concentrated on both sides of the Fujia River, while the areas with low are distributed in most areas in the west of the basin. The Pearson's correlation factor was 0.0583 in the original DRASTIC model, 0.1113 in the DRASTIC-LY method and 0.8291 in the modified DRASTIC-LY model, which indicated that the revised DRASTIC-LY model was more appropriate than the original model. The results can help the government with the protection of water resources.

RELIABILITY OF GEOSPATIAL PARAMETRIC MODELS IN AQUIFER SUSCEPTIBILITY MAPPING: CASE STUDY OF ILE OLUJI SOUTHWESTERN NIGERIA

The usefulness of groundwater vulnerability mapping cannot be overemphasized in planning, policy formulation and decision-making for groundwater management and protection. The present study employed geographic information system based overlay and index methods (DRASTIC, DRASTIC-LU, GOD and AVI models) in assessing and mapping groundwater vulnerability zones in Ile Oluji area of Ondo State, Southwestern Nigeria. The models’ parameters were prepared using hydrogeological (well/borehole) data, geophysical data, and satellite imageries. The weightage of different parameters was done using analytical hierarchy process. The DRASTIC map classified the area into the low vulnerability (30 % of the area), moderate (4%), high-vulnerability zone (60 %), and very high vulnerability zone (6 %). The DRASTIC-LU distinguished the area into high – very high groundwater vulnerability zone (90 %), while low – moderately low area has 10 % aerial extent. The GOD and AVI models, categorized the vulnerable areas into quite low (<0.03) to low (0.03 – 0.3); and high (0.98 – 1.85) to extremely high (<0.98) vulnerability zones respectively. As a result, the DRASTIC, DRASTIC-LU, and AVI models all showed predominate high vulnerability zone, which was also confirmed by the nitrate map. The index values in the DRASTIC and DRASTIC-LU models revealed significant overlap. Therefore, in the research region, slope, hydraulic conductivity, net recharge, soil medium, and depth to water level are the factors that have the greatest influence on groundwater quality. Due to the significant number of highly vulnerable places, the aquifers must be protected immediately.

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.

Assessing recharge process in plain catchments using isotopic and hydrochemical techniques

In order to increase the sustainability and conservation of water resources, a joint approach of isotopic and hydrochemical techniques was attempted to identify and quantify water sources and favourable recharge areas that would explain the integral functioning of a typically plain catchment. Chloride and δ18O and δ2H were measured in rain, groundwater, and pond samples. Chloride mass balance approach was applied to calculate the recharge and mixed water calculation was carried out using conservative tracers. Also, the local meteoric water line was calculated. Depleted isotopic and slightly progressive chloride contents are observed and they are grouped around to the local meteoric water line in the upper part and in the west of the lower catchment. In the East lower area 20% of recharge is calculated; isotopes are more enriched and lower concentration of chloride are observed. Depleted isotopic fingerprint and low salinity concentration for Ballenera pond were identified in a well close to it. This work demonstrates that in very flat zones, small changes in the hydrologic fluxes can impact on the water table of surface waters and groundwaters, leading to establish very local recharge zones that hardly can be recognized in large scale or esatfrequency of measurement, but can quiet easily be identified when chemical conservative tracers and water stable isotopes are used. Also, isotopic data demonstrate the importance of shallow wetlands as certain recharge areas to the regional aquifer, becoming areas of high groundwater vulnerability.

Assessment of groundwater vulnerability based on the modified DRASTIC model: a case study in Baicheng City, China

Accurate assessment of groundwater vulnerability objectively reflects an area’s potential for groundwater pollution and provides a reference basis for pollution control and prevention. The main objective of this study was to modify the original DRASTIC model to improve the consistency of groundwater vulnerability assessment results with regard to the actual conditions of the study area. To optimize the assessment objectivity, two additional factors that are influenced by human activities (land use and degree of groundwater extraction) were added to form the DRASTICLE model. Then, based on the correlation between all factors and measured nitrate concentrations, the improved three-scale analytic hierarchy process (AHP) and the weights of evidence (WOE) methods were used to reassign the factor weights of the DRASTICLE model. The area under the receiver operating characteristic (ROC) curve, denoted as AUC, was used to quantitatively evaluate the accuracy of all four models (original DRASTIC model AUC: 0.62). By modifying the factors and weights, the three new models showed better performance, AUC values were 0.64, 0.73 and 0.85 for the DRASTICLE, AHP-DRASTICLE, and WOE-DRASTICLE models, respectively. These results indicate that the modified models could more accurately convey groundwater vulnerability in the study area. The WOE-DRASTICLE model, which had the best performance, was then used to assess groundwater vulnerability in 2000 and 2010 and these were compared to 2018. In 2000, 2010, and 2018, the proportion of areas with very high groundwater vulnerability was 5%, 6%, 8%, respectively. Meanwhile, the proportion of areas with very low vulnerability decreased from 73 to 75%, and then rose to 82%, indicating that the spatial distribution of groundwater vulnerability has changed over time. Findings of this study are expected to provide a new theoretical basis for the Baicheng City municipal government in China to better manage and exploit groundwater resources.

A modified approach to quantify aquifer vulnerability to pollution towards sustainable groundwater management in Irrigated Indus Basin.

The quality of groundwater in the study watershed has worsened because of industrial effluents and residential wastes from the urbanized cities; therefore, there is an important need to explore the aquifer vulnerability to pollution for sustainable groundwater management in the Irrigated Indus Basin (IIB). This study proposed a novel methodology to quantify groundwater vulnerability using two fully independent methodologies: the first by reintroducing an improved recharge factor (R) map and the second by incorporating three different weight and rating schemes into a traditional DRASTIC framework to improve the performance of the DRASTIC approach. In the current study, we composed a recharge map from Soil and Water Assessment Tool (SWAT) output (namely SWAT recharge map) with a drainage density map to retrieve an improved composite recharge map (SWAT-CRM). SWAT-CRM along with other thematic layers was combined using weightage overlay analysis to prepare the maps of groundwater vulnerability index (VI). The weight scale (w) and rating scale (r) were assigned based on a survey of available literature, and we then amended them using the analytical hierarchy process (AHP) and a probability frequency ratio (PFR) technique. Results depicted that the region under high groundwater vulnerability was found to be 5-22% using traditional recharge maps, while those are 9-23% using improved SWAT-CRM. The area under the curve (AUC) revealed that groundwater vulnerability zones predicted with SWAT-CRM outperformed the DRASTIC model applied with the traditional recharge map. Groundwater electrical conductivity (EC) was>2500 mS/cm in the high groundwater vulnerability zones, while it was <1000 mS/cm in the low groundwater vulnerability zones. The outcomes of this study can be used to improve the sustainability of the groundwater resources in IIB through proper land-use management practices.

Groundwater vulnerability assessment and mapping in shallow groundwater

The increasing population density can contaminate groundwater. So far, groundwater is still the primary source to fulfill clean water and drinking water in Muntilan, Salam, and Ngluwar Sub-District. Studies on groundwater vulnerability are essential to minimize the contamination risks as a piece of basic information for land use planning. This research aims to assess groundwater vulnerability in Muntilan, Salam, and Ngluwar Sub-District. The simple vertical vulnerability (SVV) method with GIS was selected to develop a groundwater vulnerability map. The parameters of this method consist of the type of soil/rock, the thickness of the water-unsaturated zone, and the recharge value. The results show that the research area can be divided into three vulnerability classes: very low, moderate, and high groundwater vulnerability. Very low groundwater vulnerability has a value of more than 70 with very high protection effectiveness. The class is distributed in Muntilan and Salam Sub-Districts. Moderate groundwater vulnerability has a value less than 35 to 65 with moderate protection effectiveness, and high groundwater vulnerability has a value ranging from 24 to 35 with low protection effectiveness. Both of the class is evenly distributed in Muntilan, Ngluwar and Salam Sub-Districts.

Depth–Sequential Investigation of Major Ions, δ18O, δ2H and δ13C in Fractured Aquifers of the St. Lawrence Lowlands (Quebec, Canada) Using Passive Samplers

General and isotopic geochemistry of groundwater is an essential tool to decipher hydrogeological contexts and flow paths. Different hydrogeochemical patterns may result from the inherent physical aquifer heterogeneity, which may go unnoticed without detailed investigations gathered from multilevel or multiple observation wells. An alternative to overcome the frequent unavailability of multiple wellbores at sites is to perform a detailed investigation on the single wellbore available. In this perspective, the aim of this study is to use passive samplers to sequentially collect groundwater at depths in long–screened wellbores. Such investigation is carried out for major ions and stable isotopes compositions (δ2H, δ18O, δ13C) at ten sites in the context of fractured carbonate aquifers of the St. Lawrence Lowlands (Quebec, Canada). The information gathered from the calco–carbonic system, major ions and stable isotopes report poorly stratified and evolved groundwater bodies. Contribution of water impacted by anthropogenic activities, such as road salts pollution and carbon sources from C4 vegetation, when they occur, are even observed at the greatest depths. Such observations suggest quick flow paths and efficient mixing conditions, which leads to significant contributions of contemporary groundwater bodies in the fractured aquifers investigated down to depths of about 100 m. Although physical aquifer investigation reported few and heterogeneously distributed fractures per wellbore, hydrogeochemical findings point to at overall well interconnected fracture networks in the aquifer and high vulnerability of groundwater, even at significant depths.

Hydrogeological Risk Assessment for Groundwater Conservation in the Northeastern Slope Area of Mount Arjuno, Pasuruan Regency, East Java, Indonesia

The northeastern slope of Mount Arjuno, Pasuruan district, East Java province, Indonesia represents a vast and good groundwater resource quality, generally be exploited by some companies for drinking water industries. Water unbalance and quality degradation is presumed to arise because groundwater extraction volume is getting bigger but less control by the regency authority. This study is to figure out the geologic condition and hydrogeological system, conduct groundwater exploitation risk assessment, and develop a conservation program. The study results show that the study area's geomorphological units can be divided into the volcanic summit, volcanic slope, fluvial plain, and anticlinal hills. The lithology comprises sandstone, breccia, and andesite lava of Mount Arjuno and Mount Welirang. The geological structures are anticline, normal fault, and lateral slip fault. Hydrologically, there are three watersheds, including Lumbangrejo, Ketanireng, and Prigen watersheds. The aquifers comprise unconfined to semi-confined aquifers with fissures and intergranular porosity. Based on risk assessment valuation, Pecalukan village of the Ketanireng watershed and Lumbangrejo village of the Lumbangrejo watershed are categorized as very high groundwater vulnerability zones, Karangrejo and Sukoreno villages of the Lumbangrejo watershed, Kedungringin, Kepulungan, and Gunungsari villages of the Ketanireng watershed are categorized as medium vulnerability zone. While, Ngorong village of the Lumbangrejo watershed, Gempeng, Oro-Ombo, Kalisat, and Dukuhsari villages of the Prigen watershed belong to the low vulnerability zone. The proposed conservation programs involve profitable water use safety campaigns, domestic waste, and industrial wastewater management, agricultural activities controlling, sandstone mining regulation, and reforestation.

A GIS-based Assessment of the Vulnerability to Potential Pollution of the Alluvial Aquifer of Aousja-Ghar El Melh (North-East of Tunisia) Using the Parametric Method DRASTIC

The phreatic aquifer of Aousja-Ghar El Melh (governorate of Bizerta, northeast of Tunisia), has a great economic weight as it is tightly linked to irrigation and domestic consumption. The aquifer area is found mostly in agricultural zones where more and more chemical fertilizers are being used. Such chemical fertilizers, alongside industrial zones discharges appearing for the last 25 years, put at risk ground waters quality. The DRASTIC method has been applied to study the extent to which the aquifer has been affected by generic pollutants. This method hinges on GIS techniques. The result suggests a map with evidence for three degrees of vulnerability: low, moderate, and high. Evidence shows the predominance of moderate vulnerability in most of Aousja-Ghar El Melh aquifer, which occupies an area of 45%. Low and high groundwater vulnerability occupy 28% and 27% of the total surface of the studied area, respectively.

A GIS-based Assessment of the Vulnerability to Potential Pollution of the Alluvial Aquifer of Aousja-Ghar El Melh (North-East of Tunisia) Using the Parametric Method DRASTIC

The phreatic aquifer of Aousja-Ghar El Melh (governorate of Bizerta, northeast of Tunisia), has a great economic weight as it is tightly linked to irrigation and domestic consumption. The aquifer area is found mostly in agricultural zones where more and more chemical fertilizers are being used. Such chemical fertilizers, alongside industrial zones discharges appearing for the last 25 years, put at risk ground waters quality. The DRASTIC method has been applied to study the extent to which the aquifer has been affected by generic pollutants. This method hinges on GIS techniques. The result suggests a map with evidence for three degrees of vulnerability: low, moderate, and high. Evidence shows the predominance of moderate vulnerability in most of Aousja-Ghar El Melh aquifer, which occupies an area of 45%. Low and high groundwater vulnerability occupy 28% and 27% of the total surface of the studied area, respectively.

Groundwater Vulnerability in the Piedmont Region under Climate Change

Groundwater vulnerability has increased in recent decades due to several factors, but mainly due to climate change. In this study, we applied a complex approach to determine groundwater vulnerability at a regional scale in the Piedmont region including high-resolution climate models. Aquifers, terrain model, climate data, land cover, and groundwater monitoring stations data of nitrate (NO3) concentration were the main layers used for the vulnerability and risk mapping. Validation of the groundwater vulnerability map consisted of pixel pair comparison (PPC) using the quality status of a monitored groundwater station, dating from 2005 to 2012. The groundwater vulnerability maps that related to the 1990s and 2020s periods indicated very high and high vulnerability of groundwater in the central and eastern parts of the region, especially in the porous aquifers of Po Plain. The areas with very low and low vulnerability extend into the north and west, mainly in the non-aquiferous media and fissured aquifers. The future scenarios of groundwater vulnerability indicate a consistent increase of the very high vulnerability class, from the 1990s to the 2050s periods, in all scenarios, and mainly in the Po Plain.

Combining quantity and quality controls to determine groundwater vulnerability to depletion and deterioration throughout South Africa

Groundwater vulnerability is normally associated with the potential for contamination, for example the DRASTIC approach, but the increasing importance of groundwater in human, agricultural, and industrial systems, implies that groundwater vulnerability is dependent on a range of other parameters and particularly parameters impacted by climate change. A robust method for evaluating groundwater vulnerability therefore requires the incorporation of multiple indices into one holistic evaluation. In this study, a model for groundwater vulnerability in South Africa was developed, calculating the combined weighted averages of nine spatial datasets; namely: (1) mean annual precipitation, (2) mean annual surface temperature, (3) tritium distribution in groundwater, (4) potential evaporation, (5) aquifer type and yield, (6) terrain slope, (7) electrical conductivity, (8) population density and (9) cultivated land use. The model was run through 36 different weighting scenarios and indicates that on average 22.4% of South Africa’s groundwater is predicted to have a very high vulnerability to depletion in quantity and deterioration in quality (12.2% very low; 35.4% low; 16.8% moderate and 13.1% high). A single weighting scenario (M-I/C-2/P-2) was chosen that showed good alignment to the previous assessments that predicted that 20.9% of groundwater resources in South Africa have very high vulnerability (1.5% very low; 35.7% low; 24.9% moderate and 17.0% high). The model was adjusted to reflect climate conditions 50 years into the future, resulting in a 3% increase in very high vulnerability areas and a 6% decrease in low vulnerability areas. The results suggest that large areas of South Africa have high groundwater vulnerability, especially in areas where groundwater supplements domestic supply and agriculture. The implementation of this method to evaluate groundwater vulnerability across diverse natural environments and political boundaries will supplement comprehensive groundwater vulnerability assessments and the development of effective groundwater management policy.

Study of groundwater vulnerability to contamination using the DRANTHVP method in wates groundwater Basin, Indonesia

Wates Groundwater Basin in Kulon Progo Regency, the Special Region of Yogyakarta, covers an area of 152.67 sq.m. With human occupations continuously growing in the regency, the groundwater in this basin is subject to change. This research was intended to identify the spatial distribution of groundwater vulnerability of Wates Groundwater Basin using the DRANTHVP method, which factors in Depth to Water Table (D), Recharge (R), Aquifer Thickness (A), Nitrate Attenuation Intensity (N), Topography (T), Groundwater Velocity (V), and Pollutant Input Intensity (P). The data were analyzed quantitatively using a weighted tiered approach―the rating was based on to what degree each of these factors contributes to the calculated vulnerability, then overlaid to produce a groundwater vulnerability map. From the analysis, the index values were clustered into three classes of groundwater vulnerability: low 4.48-6.35, medium 6.35-7.39, and high 7.39-7.97. A large proportion of the basin had medium groundwater vulnerability (109.16 sq.m), and less than half of it had low (39.63 sq.m) and high groundwater vulnerability (3.88 sq.m); these severity levels vary depending on the hydrogeological characteristics and land use of a study area.

Using an expert-based model to develop a groundwater pollution vulnerability assessment framework for Zimbabwe

Predicting groundwater vulnerability to pollution in countries with sparse data is difficult. Using Zimbabwe as a case study, this study presents a simple expert-based GIS model that incorporates seven natural and anthropogenic factors for modelling groundwater vulnerability at a national scale. The predicted groundwater vulnerability was tested against three water quality parameters: pH, total nitrates and Total Dissolved Solids (TDS). The agreement between predicted vulnerability and measured groundwater quality was reasonably high for pH and total nitrates (R2 ≥ 0.54, P < 0.05). For the dissolved solids, the relationship between vulnerability predicted by the model and measured TDS was weak (R2 = 0.33). Model predictions indicate spatial variability of groundwater vulnerability to pollution, with high pollution in Mazowe and Manyame catchments dominated by high urban land use and commercial agriculture. Moderately high vulnerability of groundwater to pollution was predicted for Mzingwane and Runde catchments, whereas the lowest vulnerability of groundwater to pollution were predicted for the lower Sanyati sub-catchment and Gwayi catchment. The advantage of the expert-based GIS model presented here is that it requires only a limited and widely available input data set. Hence, it can be used in other countries with limited hydrogeological data to generate results showing spatial variability of groundwater vulnerability to pollution to guide sustainable groundwater management. We, however, recommend further research with case studies focusing on the most vulnerable catchments such as Mazowe, and more extensive validation of parameters, especially TDS, to improve the proposed model.

Groundwater vulnerability assessment in the Grand Est region, France

Groundwater represents the most important freshwater resource. In this paper, we applied a spatial approach based on the Geographical Information Systems (GIS) technology to assess the groundwater vulnerability in the Grand Est region from northeastern France. Aquifers media (AM), potential infiltration map (PIM), pollution load index (PLI), and effective precipitation (EP) were the main parameters used in the calculation of groundwater vulnerability. This study proposes a spatial-temporal analysis including past (1961–1990), near future (2011–2040), and more distant future (2041–2070), thereafter called the 1990s, the 2020s, and the 2050s. To validate the results, groundwater monitoring stations data of Nitrate (NO3−), dated from 2005 to 2012, was used as reference datasets. The validation of the groundwater vulnerability map was based on pixel pair comparison (PPC) method and it indicates 42.85% perfect confidence and 50% good confidence for the groundwater vulnerability map in 2020s period. The high groundwater vulnerability was found in the Rhine, Marne, and Aube Valleys, while the low and very low vulnerability was depicted in the Vosges, Ardennes Mountains, and some territories form the central region for all three periods. Application of the proposed framework indicates increases of vulnerability up to 60% between 1990s and 2020s and up to 80% between 1990s and 2050s scenarios. The output maps and findings could be useful for the future environmental plans of the region and, in addition, could help mitigate the problems related to water resources, considering the climate expectations.