Intrinsic Vulnerability Mapping Research Articles

O Uso da Geoestatística na Avaliação dos Parâmetros Hidrogeológicos para Compor o Mapa de Vulnerabilidade Intrínseca de Aquíferos

The aim of this study is to perform a geostatistical estimation of hydrogeological parameters to compose the intrinsic vulnerability map for an aquifer. The study presents an exploratory analysis of well data extracted from the Groundwater Information System (SIAGAS), which refer to parameters such as degree of confining, lithology and static level. Therefore, initially, among other procedures, we look for inconsistent data, we produce descriptive statistics and we also apply a normality test to the dataset. The following steps were to make up the primary space description of the respective parameters based on the corresponding identified patterns, randomness and grouping of well data in addition to exploring the existence of a tendency along certain directions. After the preliminary steps, the geostatistical methodology is then applied divided into three phases. The first refers to the variogram study, characterized by the construction of the experimental variograms. In the second phase, automatic adjustment is made to these variograms for three mathematical models: spherical, exponential and gaussian. Then, by cross validation, the performance is estimated for the different models adjusted using statistical indicators. After validation of these models, the last phase takes place, in which we perform the geostatistical estimation by kriging. The estimated values of hydrogeological parameters, when jointly multiplied, composes the estimation of the intrinsic vulnerability index illustrated in the form of a map. This proposal was applied in an area partially covering the city of Belem. The results showed that the methodological approach represents an excellent planning and management tool for the protection of groundwater aquifers.

Evaluation of intrinsic vulnerability, hazard and risk mapping for karst aquifers, Khorein aquifer, Kermanshah province: a case study

The Khorein karstic aquifer in the Kermanshah province (western Iran) plays a vital role in providing drinking and agricultural water for its surrounding communities. The aim of this research is to evaluate natural vulnerability, hazard and risk indices of the Khorein aquifer by cost action 620 proposed models, as well as to prioritize the aquifer surface concerning to protection measures and providing management strategies in order to its better protection. The results of the COP method represent the high natural vulnerability of the region. Calculation of the hazard index show that the military regions, telecom sites, the nomads’ habitation areas and quarries are situated in areas with low hazard index. Evaluation of the risk index and predict the aquifer contamination show that 75 % of the region extent is no or very low contamination risk, which this is due to low development of human activities in the top of the mass. This claim is confirmed by the presence of Escherichia coli bacteria in the aquifer water. The expansion of human activities in future toward the altitudes, can lead to further pollution of the aquifer. Continuous monitoring of the chemical characteristics of water, taking the recharge map, characterizing the areas with concentrated charge, determining the karstic landform limits, restricting the livestock activities on the anticline top, avoiding the construction activities close to the aquifer and improving the people and authorities public awareness level are the main necessary measures pertaining to manage the Khorein aquifer.

Vulnerability mapping and protection zoning of karst springs. Validation by multitracer tests

Protection zoning of karst springs and wells used for water supply is a key aspect in many countries, calling for specific methodologies adapted to the particular characteristics of karst media. This work presents a new approach, in view of the present state of the art and based on experiences with contamination vulnerability mapping at the pilot site of the Villanueva del Rosario karst system (southern Spain). Source (intrinsic) vulnerability maps were prepared and compared using three European procedures for karst aquifers. The vulnerability maps were then tested using dye tracers. The COP+K method and Slovene Approach appear to provide reliable results in terms of intrinsic vulnerability mapping. Nevertheless, all the methods have a margin of error. The COP+K map is adopted as the baseline to delineate the protection zones, through the conversion from vulnerability classes to degrees of protection.

Hydrogeological investigations and groundwater vulnerability assessment and mapping for groundwater resource protection and management: State of the art and a case study

The available literature was used in this work to review the methodologies for groundwater vulnerability mapping. The objective of the literature review was to define the vulnerability concept and to discuss the best way to establish aquifer vulnerability maps and the utilities of these maps for groundwater protection. In this study, we explore the hydrodynamic properties of the Grombalia aquifer system in north Tunisia to evaluate the vulnerability of groundwater. The established vulnerability maps are used for groundwater managing and protection. In Grombalia basin, the groundwater resource is used for agriculture and drinking purposes. The intrinsic vulnerability of the phreatic aquifer of Grombalia is mapped using the standard DRASTIC, a modified DRASTIC and a DRIST model. The adopted methodology for the intrinsic vulnerability mapping is based on the hydrogeological system properties. The vulnerability index calculation was used to establish a map with areas of vulnerability degree. This method is based on the combination of various topographical, lithological and hydrogeological data using Geobased Information System software. These methods consider the attribution of a numeric index to each considered parameter. In the established map, 26% of the aquifer extension is vulnerable according to standard DRASTIC model. The modified DRASTIC method, which considers the vadose zone heterogeneity and the aquifer geometry, showed that 17% of the studied area is occupied by a high vulnerability. The application of the DRIST model showed a high vulnerability in area covering 66% of the extension of the shallow aquifer of Grombalia. This important vulnerability is due mainly to vertical parameters implicated in the infiltration of the pollutant. The established vulnerability maps provide recommendations for groundwater resource protection in the aquifer system of Grombalia. We conclude that the three used models for vulnerability assessment and mapping reveal the susceptibility of the aquifer system to the special effects of pollutants.

Total vulnerability estimation for the Tabriz aquifer (Iran) by combining a new model with DRASTIC

Groundwater vulnerability mapping is an important key for improving the planning and decision-making processes in order to prevent groundwater contamination. The main objective of this research was to delineate the groundwater total vulnerable zones within the Tabriz aquifer in the northwest of Iran. So, the groundwater intrinsic vulnerability map was created by overlaying the layouts obtained from the DRASTIC parameters. In this research, a new method for evaluation of specific vulnerability was also applied. In this method, five parameters (density of population, recharge by rivers, agriculture, industry and abstraction) were determined and assigned a suitable weight and rates to each parameter to obtain the specific vulnerability index of the aquifer. Finally, the intrinsic and specific vulnerability maps were combined to develop the groundwater total vulnerability map. The resulting map shows that the east and northeast of the Tabriz aquifer is more vulnerable than the other parts. To confirm the vulnerability distribution, 53 samples of groundwater nitrate concentration were plotted on the resulting total vulnerability map which showed that the northeast and east parts of Tabriz aquifer (High and moderate vulnerability zones) have higher nitrate concentration relative to the rest of the Tabriz aquifer which is located in the low vulnerability zones. Application of DRASTIC+DRAIA method to another aquifer confirmed the good accuracy of this method in evaluation of the total vulnerability.

DRASTIC-GIS model for assessing vulnerability to pollution of the phreatic aquiferous formations in Douala–Cameroon

The pollution potentials of the aquiferous formations in Douala was obtained by evaluating the aquifer vulnerability. Aquifer vulnerability is an intrinsic property of groundwater which gives the possibility of percolation and diffusion of contaminants from the ground surface into the subsurface. Aquifer vulnerability to pollution was evaluated for the phreatic aquifer in Douala using the DRASTIC method. DRASTIC is a groundwater quality model representing; Depth to Water, Net Recharge, Aquifer Media, Soil Media, Topography, Impact of vadose Zones, and Hydraulic Conductivity. From data, five thematic maps were generated and an intrinsic vulnerability map was developed based upon calculations of DRASTIC Indices (D.I). The D.I for the different inhabited quarters were; Bonamoussadi (BS)=145, Bali (BA)=138, Bonapriso (BP)=140, Airport(AP)=129, Ndogbong(ND)=120, Bepanda(BE)=130, Vallee Besengue (VB)=134, New Bell (NB)=125, Bonassama BM)=128 and Rail(RA)=167. ArcGIS quantile classification subdivided the area into four groups; very low, low, moderate and high ground water vulnerability risk zones covering about 30%, 30%, 20% and 20% of the study area respectively. An in-depth study is recommended to give a detailed perspective to the evolution and nature of actual pollution in the area.

Evaluation of groundwater vulnerability in the lower Varuna catchment area, Uttar Pradesh, India using AVI concept

Groundwater vulnerability assessments calculate the sensitivity of quality of groundwater to an imposed contaminant load which is essential element of the aquifer management plans. Seventy five groundwater samples have been analyzed for different chemical parameters to understand the groundwater quality of the lower Varuna river basin, Uttar Pradesh, India. The intrinsic groundwater vulnerability map of the lower Varuna catchment area in the north of the city of Varanasi (India) shows a high dependency on the depth to groundwater. The topmost layer of alluvial silty clay, protects the groundwater against contamination in this urban area, but the retention time in the unsaturated zone can be estimated to several months only. The input dataset is very sparse i.e. groundwater levels were measured twice (pre- and post-monsoon 2009) and the geological map shows only alluvium as the outcrop. Several boreholes in this area show, that the alluvium has a thickness of about 4 m and below that are fine grained sands. The surface information does not allow the development of a risk map since land use changes very fast and contamination areas can not be identified accurately. The vulnerability maps developed in this study have become important tools for environmental planning and predictive management of the groundwater resources in the fast urbanizing region in the Varanasi area.

Groundwater Vulnerability and Hazard Mapping in an Arid Region: Case Study, Amman-Zarqa Basin (AZB)-Jordan

The importance of groundwater portability and the possible sources of anthropogenic contamination have led to the development of intrinsic groundwater vulnerability mapping. In this study, groundwater vulnerability map for Amman Zarqa Basin (AZB) has been generated based on information derived and calculated from processed remote sensing information and laboratory analysis. The database was prepared from soil hydro geological and hydrological data, Digital Elevation Model (DEM), and geological maps. For assessment of groundwater vulnerability, the method proposed by the state geological surveys of Germany (GLA-method) has been adapted and applied. The vulnerability map shows about 77% which is about 2919 Km2 of the AZB is classified as very low to low which could be corresponding to the pollution sources due to the absence of potential hazards and also due to low vulnerabilities. These areas could consequently be interesting for future development as they set preferable in view of ground water protection. In addition, about 14% (530 km2) is classified within the moderate vulnerability zone. About 5% (around 19 km2) of the study area lies under the area of high vulnerability zone. Only 4% can be classified as very high risk areas. Groundwater quality results revealed that water leach ate from point source is the main cause for groundwater contaminations in highly vulnerable karstic limestone aquifer (Amman Wadi Es Sir Aquifer-B2/A7). On the other hand, the Kurnub Sandstone aquifer (K) is generally well protected in the central and eastern part of the AZB due to its thick cover of partly marly sequences. However, the Kurnub aquifer might have a potential risk from the recharged infiltrating surface water from the Zarqa River, which is highly polluted due to industrial activities located along the river.

Abandoned water resources as potential sources of drinking water – the Korentan karst spring near Postojna

In the area of the Orehek karst intrinsic vulnerability maps of groundwater and the Korentan karst spring, hazard maps and risk to contamination map have been made using Slovene Approach. For this purpose cartographic and other published data on geological, geomorphological, pedological, hydrological and meteorological characteristics have been gathered and extensive field inventory of the missing geomorphological and pedological characteristics has been made. Publically available land use and census data have been examined and checked in the field, manure heaps and illegal waste dumps have been mapped. The final thematic maps are excellent tools for national and local authorities when planning water protection and land use. The presented study in the catchment of an actual water source is an example of good practice of the revival of the in the past abandoned water sources that can in the future serve as a substitution water source in case of main water source overexploitation or contamination.

Intrinsic vulnerability mapping for small mountainous karst aquifers, implementation of the new PaPRIKa method to Western Pyrenees (France)

The new intrinsic vulnerability mapping method PaPRIKa is proposed as a tool to assess groundwater protection of small karst systems exploited for drinking water supply purposes in the French Pyrenees. The specific characteristics of the discontinuous carbonate aquifers of mountainous areas are here considered and taken into account into the implementation of the methodology. The Orbe site from the French Western Pyrenees area is chosen as a test site because of the relatively well known structure and behavior of the aquifer system. Steep slopes, extremely developed dissolution features, thin soils and strong dipping of geological formations are the main points to be considered. PaPRIKa method appears as a tool to assess and illustrate both the resource and source vulnerability according to the site specificities provided that appropriate field observations at a relatively high density are carried out. The vulnerability of the resource was assessed for the entire catchment area, while source-orientated mapping was attempted for the catchment area of the main capture work used for drinking water supply.

Groundwater Vulnerability Assessment and Validation for a Fast Growing City in Africa: A Case Study of Lagos, Nigeria

Lagos is the world’s sixth largest city, the most populous city in Africa and the most populous city inNigeria. A total of eighteen groundwater exploitation borehole logs together with hydrogeological and geotechnical data were used for the study. The eighteen available borehole logs were categorized into seven areas spanning the shoreline to inland boundary ofLagosState. The study area has a high net recharge of1838 mm/yr and the aquifer media is sand. The intrinsic vulnerability map show areas of highest potential for groundwater pollution based on hydro-geological condition and human impacts. Seven major hydro-geological factors incorporated into DRASTIC model and the geographic information system (GIS) were used to create a groundwater vulnerability map by overlaying the available hydro-geological data. The output map shows that the southeast of the aquifer is under very high vulnerability while central parts of aquifer have high vulnerability. Other parts (north, northwest and south) of the study area have moderate vulnerability to pollution. For testing of the vulnerability assessment, groundwater quality data were collated from literature for the different vulnerability zones of the study area. The chemical analysis results show that both the southeast and northwest west parts of study area aquifer (very high and moderate vulnerability zones) have higher nitrate concentration relative to the rest of aquifer, that are located in high vulnerability zone. The validation of the DRASTIC models was accomplished through pair wise comparison of DRASTIC vulnerability maps (using Pearson’s r correlation coefficient) with a total of 14 layers representing original DRASTIC input data, Land cover (LC) features, and groundwater TDS, Cl- and NO3 data. Results from the correlation analysis indicate a significant association between high groundwater TDS, NO3 concentrations and distances from certain LC types.

Groundwater intrinsic vulnerability and risk mapping

Groundwater vulnerability mapping is an important key to improving planning and decision-making processes in order to prevent groundwater contamination. This study generates groundwater vulnerability maps for the Izeh Plain in Iran using a modified Drastic model, geographical information system and remote sensing data. Sensitivity analysis was used to assign weight by showing the importance of each parameter in the Drastic model. The highest weight (5) was assigned to the aquifer media factor of the model, which had the highest mean value (4·53), and the lowest weight was assigned to the topography factor. The resulting maps revealed that the groundwater is highly vulnerable in the southwest Izeh Plain.

Assessment of groundwater contamination risk using hazard quantification, a modified DRASTIC model and groundwater value, Beijing Plain, China

Groundwater contamination risk assessment is an effective tool for groundwater management. Most existing risk assessment methods only consider the basic contamination process based upon evaluations of hazards and aquifer vulnerability. In view of groundwater exploitation potentiality, including the value of contamination-threatened groundwater could provide relatively objective and targeted results to aid in decision making. This study describes a groundwater contamination risk assessment method that integrates hazards, intrinsic vulnerability and groundwater value. The hazard harmfulness was evaluated by quantifying contaminant properties and infiltrating contaminant load, the intrinsic aquifer vulnerability was evaluated using a modified DRASTIC model and the groundwater value was evaluated based on groundwater quality and aquifer storage. Two groundwater contamination risk maps were produced by combining the above factors: a basic risk map and a value-weighted risk map. The basic risk map was produced by overlaying the hazard map and the intrinsic vulnerability map. The value-weighted risk map was produced by overlaying the basic risk map and the groundwater value map. Relevant validation was completed by contaminant distributions and site investigation. Using Beijing Plain, China, as an example, thematic maps of the three factors and the two risks were generated. The thematic maps suggested that landfills, gas stations and oil depots, and industrial areas were the most harmful potential contamination sources. The western and northern parts of the plain were the most vulnerable areas and had the highest groundwater value. Additionally, both the basic and value-weighted risk classes in the western and northern parts of the plain were the highest, indicating that these regions should deserve the priority of concern. Thematic maps should be updated regularly because of the dynamic characteristics of hazards. Subjectivity and validation means in assessing the vulnerability result were also discussed. In addition, GIS technology was essential in completing the assessment work.

Modified DRASTIC assessment for intrinsic vulnerability mapping of karst aquifers: a case study

Groundwater in karstic aquifers can be dangerously sensitive to contamination. In this paper, DRASTIC assessment was modified and applied, for the first time, to address the intrinsic vulnerability for karst aquifers. The theoretical weights of two of DRASTIC’s parameters (aquifer media and hydraulic conductivity) were modified through sensitivity analysis. Two tests of sensitivity analyses were carried out: the map removal and the single parameter sensitivity analyses. The modified assessment was applied for the karst aquifers underlying Ramallah District (Palestine) as a case study. The aquifer vulnerability map indicated that the case study area is under low, moderate and high vulnerability of groundwater to contamination. The vulnerability index can assist in the implementation of groundwater management strategies to prevent degradation of groundwater quality. The modified DRASTIC assessment has proven to be effective because it is relatively straightforward, use data that are commonly available or estimated and produces an end product that is easily interpreted.

Assessment of groundwater risk using intrinsic vulnerability and hazard mapping: Application to Souassi aquifer, Tunisian Sahel

Abstract Special attention has been paid to risk assessment in water resource management in arid and semi-arid regions like the Souassi aquifer, Tunisia. Risk assessment, using vulnerability and hazard mapping, is considered as a fundamental aspect of sustainable groundwater management. To determine the degree of risk affecting the study area, an attempt has been made to combine hydro-geologic parameters using the DRASTIC method and the hazard assessment by taking the product of the weighted hazard value ( H I ), the ranking factor ( Q N ) and the reduction factor ( R f ). All parameters used in this risk assessment were prepared, classified, weighted and integrated in a GIS environment. Data treatment shows that large areas in the Souassi aquifer can be classified as high or very high risk areas corresponding to pollution sources located in high vulnerability zones. The areas with low and very low risk are situated in the south, which could, consequently, be interesting for future development and long term planning of protective measures. Sensitivity analyses indicated that the removal of groundwater depth, net recharge and aquifer media parameters from the DRASTIC index, causes large variation in vulnerability assessment. Moreover, hydraulic conductivity and topography were found to be more effective in assessing aquifer vulnerability. Therefore, they should have higher weights than those assumed by the DRASTIC standard method, and contrary to the impact of the vadose zone parameter. The validity of the DRASTIC and the risk methods, verified by comparing the distribution of nitrates in the groundwater and the different vulnerability classes, shows a high similarity.

PaPRIKa: a method for estimating karst resource and source vulnerability—application to the Ouysse karst system (southwest France)

The intrinsic vulnerability mapping method, PaPRIKa, is proposed as a common basis for karst groundwater protection in France. PaPRIKa is a specialized method for studying karst aquifers, derived from updating the RISKE and EPIK methods. Both the structure and functioning of karst aquifers are considered in order to develop a resource and source-vulnerability mapping method. PaPRIKa means Protection of aquifers from the assessment of four criteria: P for protection (considering the most protective aspects among parameters related to soil cover, unsaturated zone and epikarst behavior), R for rock type, I for infiltration and Ka for karstification degree. The Ouysse karst system, located in the Causses area in southwest France, is one of the nine pilot sites where this method was tested and standardized. The specificities of the Ouysse system such as the size of the catchment area, the spatial variability of the karst network development, the thick infiltration zone and the system’s dual character (both karst and non-karst areas), have provided a valuable field of application. The vulnerability of the resource was assessed for the entire catchment area, while source-orientated cartography was attempted for the catchment areas of the three different capture works used for drinking water.

GIS DRASTIC model for groundwater vulnerability estimation of Astaneh-Kouchesfahan Plain, Northern Iran

In this study, the groundwater vulnerability to pollution was evaluated for Astaneh-Kouchesfahan Plain, Northern Iran using GIS DRASTIC model. Based upon available data, six thematic maps were generated and intrinsic vulnerability map was developed based upon calculations from various mapped layers and DRASTIC index. The results show that low, moderate, high and very high groundwater vulnerability risk zones cover around 12, 52, 28 and 8% of the area, respectively. Finally, in order to verify the model, the categorised DRASTIC map was compared with a categorized TDS map and the results shows that the areas including enhanced values of TDS correspond with those with higher DRASTIC ratings.

Groundwater Risk Intensity Assessment. Application to Carbonate Aquifers of the Western Mediterranean (Southern Spain)

In this work, the groundwater contamination risk is evaluated as a measure of protection for groundwater bodies intended for human consumption. For this purpose, intrinsic vulnerability maps and hazard maps of anthropogenic activities in the studied region have been taken into account. This region is constituted by carbonate aquifers that supply water to various populations. The methodology employed to determine the contamination risk was adapted from the COST Action 620 which was developed with the aim of protecting karst aquifer water. The vulnerability obtained through the PI method was modified to the COP method for the purpose of this study. The results obtained after evaluating the groundwater contamination risk show a predominance of the very low and low classes that cover more than 80 % of the study area. These areas coincide with outcrops of low permeability materials and an absence of pressures. Only 4 % of the region presents a high to very high risk of contamination which is located in areas of very high vulnerability and low to moderate pressures. These results are supported by chemical analyses of water sampled from a groundwater quality control network. Contamination risk studies are an important tool for the integrated management of groundwater and for designing protection measures. These protection measures should be incorporated into the territorial land use planning; furthermore they should define a possible plan of land uses and activities as well as establish limitations and prohibitions of impacting land uses and activities.

Karstic aquifer vulnerability assessment methods and results at a test site (Apulia, southern Italy)

Abstract. Karstic aquifers are well known for their vulnerability to groundwater contamination. This is due to characteristics such as thin soils and point recharge in dolines, shafts, and swallow holes. In karstic areas, groundwater is often the only freshwater source. This is the case of the Apulia region (south-eastern Italy), where a large and deep carbonate aquifer, affected by karstic and fracturing phenomena, is located. Several methods (GOD, DRASTIC, SINTACS, EPIK, PI, and COP) for the assessment of the intrinsic vulnerability (Iv) were selected and applied to an Apulian test site, for which a complete data set was set up. The intrinsic vulnerability maps, produced using a GIS approach, show vulnerability from low to very high. The maximum vulnerability is always due to karstic features. A comparison approach of the maps is proposed. The advantages and disadvantages of each method are discussed. In general terms, three groups can be distinguished. The GOD method is useful for mapping large areas with high vulnerability contrasts. DRASTIC and SINTACS are "any-type aquifer" methods that have some limitations in applications to karstic aquifers, especially in the case of DRASTIC. EPIK, PI, and COP, which were designed to be applied to carbonate or karstic aquifers, supply affordable results, highly coherent with karstic and hydrogeological features, and reliable procedures, especially in the case of PI and COP. The latter appears simpler to apply and more flexible in considering the role of climatic parameters. If Iv of each method is considered, the highest variability is observed in cells in the neighbourhood of karstic features. In these spatial domains, additional efforts to define more reliable and global methods are required.

Source vulnerability mapping in carbonate (karst) aquifers by extension of the COP method: application to pilot sites

A step from resource to source vulnerability mapping is presented, based on the European COST Action 620 approach for karst groundwater protection. Guidelines on vulnerability assessment of the horizontal groundwater flow path within the karst saturated zone (K factor) are proposed. By integrating this into the previously existing COP method for intrinsic resource vulnerability mapping, adequate source protection can be assessed. The proposed “Karst saturated zone (K) factor” assessment considers groundwater travel time (t subfactor), connection and contribution to the source (r subfactor) and active conduit or fissured network (n subfactor). The extended COP method was applied in two carbonate aquifers in southern Spain with different geological, hydrogeological and climate settings. The results are coherent with previous research results of the studied areas. Moreover, they are consistent with the occasional groundwater contamination detected in one of the springs. On the other hand, an absence of contamination, despite high risk, justifies the lower degrees of vulnerability assigned to the sources surveyed. The source vulnerability maps obtained can thus be used as a basis for the delineation of protection zones.