Incorporating Remote Sensing Techniques To The DRASTIC Index To Assess Groundwater Vulnerability In The Mining Area of the Rio Sonora Aquifer in Northwestern Mexico

Groundwater metal pollution is a major concern for societies, especially in areas where the mining industry is important. Index-based techniques, as the DRASTIC index, are often used to assess the intrinsic groundwater vulnerability and could be modified to evaluate the aquifer vulnerability to specific contaminants. Mines, mining wastes and related features are detectable with remote sensing techniques. In this work we evaluate the vulnerability of the Rio Sonora Aquifer to metallic pollution by the traditional DRASTIC method and by the addition of a land use (Lu) parameter in which possible sources of metals (detected by remote sensing) were considered (DRASTIC+Lu). The methodology allowed us to locate possible sources of metallic contamination. The Sonora River channel showed the higher vulnerability in both calculated vulnerability indices (DRASTIC and DRASTIC+Lu). Generally, the addition of the land use parameter caused a decrease in vulnerability but also a local increase where possible sources of metals were found. Thus, the modified method facilitated the identification of highly vulnerable areas which is relevant to better protect the studied aquifer.

Classification of Aquifer Vulnerability by Using the DRASTIC Index and Geo-Electrical Techniques

Vulnerability analysis in areas vulnerable to anthropogenic pollution has become a key element of sensible resource management and land use planning. This study is intended to estimate aquifer vulnerability using the DRASTIC model and using the vertical electrical sounding (VES) and electrical conductivity (EC) outcomes. The model allows for the identification of hydrogeological environments within the scope of the research, based on a composite definition of each environment’s main geological, geoelectrical, and hydrogeological factors. The results from the DRASTIC model were divided into four equal intervals, high, medium, low, and very low drastic index values. The SW area and NE area depict drastic index values from medium to very high, making it the most vulnerable zone in the study area, while the NW and SW areas show low to very low drastic index values. In addition, the results from the VES and EC the freshwater aquifer in the NE area and brackish water in the SE area, while the rest of the area falls into the category of brackish water. Overall, it can be concluded that areas having freshwater assemblages are on the verge of becoming contaminated in the future while the rest of the NW and SW areas constitute less vulnerable zones. The validation conducted for DRASTIC and EC shows a nearly positive correlation. Wastewater treatment policies must be developed throughout the studied region to prevent contamination of the remaining groundwater.

Evaluation of groundwater vulnerability to pollution using DRASTIC, composite DRASTIC, and nitrate vulnerability models

Background: Groundwater protection against pollution is a very important issue. Groundwater vulnerability maps are useful tools for protecting aquifers and assessing the potential for contamination. Therefore, the purpose of this study was to prepare vulnerability maps and perform sensitivity analysis to identify the most influential factors in the vulnerability of the studied aquifer. Methods: In this study, groundwater vulnerability to pollution was evaluated using DRASTIC, composite DRASTIC, and nitrate vulnerability (NV) models. Drastic is an index for the systematic assessment of potential groundwater pollution. In this method, the drastic index was calculated from the total weight and rank of the factors. For this purpose, first the factors affecting the pollution transfer, were weighted, ranked, and merged using GIS software. Then, using the overlapping techniques and after applying the necessary weight coefficients on each layer, a map of the vulnerability area of the study aquifer was prepared. Results: It was revealed that there is a significant linear relationship between all three models with the distribution of nitrate concentration. Accordingly, it was the most efficient NV model, followed by the composite DRASTIC (CD) and DRASTIC models, respectively. Also, in the studied aquifer, the DRASTIC index was between 147 and 136, the combined DRASTIC index was between 70 and 190, and the nitrate index was between 13 and 132. Conclusion: Vulnerability assessment of the studied aquifer using DRASTIC, and combined DRASTIC, and NV indices shows that, according to the DRASTIC index, 69.7% of the studied aquifer was in the medium vulnerability class. Also, according to the combined DRASTIC index, the largest area (53.62%) has low vulnerability and 31.56% has moderate vulnerability. But according to the nitrate index, 77.16% of the aquifers had very low vulnerability.

Geographical Information System Based Sensitivity Analysis Accurately Predicts Hydrocarbons Contamination Using Drastic Index and Multicriteria Analysis

<p>Among the numerous groundwater vulnerability assessment methodologies, the geographical information system-based DRASTIC model is the most widely used and have been found to achieve reliable results even in complex areas. However, hydrocarbon contamination cause by Anthropogenic activities has not previously being considered within these groundwater vulnerability assessment model.  This study proposes a new flexible approach for optimizing the identification of input data layers that can help identify vulnerability to hydrocarbon contamination through the principles of sensitivity analysis.The single-parameter (SA ) and map removal analysis(MA)  was employed to obtain effective weights for the  modified model, which were then implemented to improve efficacy Multi-criteria evaluation (MCE) techniques are part of a decision-making process for assigning weights of significance to each input layer to the DRASTIC model. The application is illustrated through a case study focussing on the city of Kano located in Northern Nigeria within west Africa .DRASTIC index model have seven paramters ,Depth of water table,net reharge ,Aquifer media ,soil media, Topography ,impact of vadose zone and hydrlauic conductivty.  The most sensitive parameters are depth of water (22.92%), net recharge, (25.98), impact of Vadose zone (27.07%),  The borehole data includes groundwater samples that were analysed for benzene, ethylbenzene and xylene (Betex) components of crude oil.  Accordingly, the results presented the highest hydrocarbon content (51.66477mg/l) in Dala (western Kano) due to the significantly high number of hydrocarbon sources such as under-storage tanks within the petroleum stations and automobile garages.</p>

Vulnerability Assessment of Water in Landfill Site and Environs: A Case Study of Olusosun in Lagos, Nigeria

This study assessed the vulnerability of landfill site in Olusosun, Lagos Nigeria using modified DRASTIC (DRASTIC L) model in a geographical information system environment. It also analyzed water samples with a view to determining the amount of trace metals concentrate present. Water samples were collected from different Boreholes and Wells with a radius of 500m to the landfill site. The modified DRASTIC (DRASTIC L) based on eight parameters such as Depth to water, Net recharge, Aquifer media, Soil media, Topography, Impact of vadose zone, Hydraulic conductivity and Distance to landfill site. The vulnerability index was calculated using a sum overlay of the eight parameters. ArcGIS 10.2 software was used to integrate all these parameters together to obtain Boreholes and Wells vulnerable zones I areas. The results showed that out of a total of 228.38 hectares, only about 47.46 hectare was observed to be within the low vulnerable zone having a DRASTIC index range between 113 – 136; while about 130.65 hectares were found to be in the moderately vulnerable zone with a DRASTIC index ranging between 136 and 144. About 50.28 hectares were within the high vulnerability zone having a DRASTIC index range between 144 and 163.Atomic Absorption Spectroscopy (AAS) was used for to test the concentrations of the heavy metals in the water samples collected and found that aside the presence of other heavy metals, Chromium was found to be present in most Wells and Boreholes measuring between 0.08 mg/L and 0.43 mg/L which is above the World Health Organization Standard of 0.05 mg/L for drinking water. This study concluded that the groundwater is contaminated and the level of pollution is directly related to the distance from the landfill.