Assessing groundwater vulnerability to contamination in Loor basin using GODS model in GIS environment

Groundwater is vulnerable to contamination by anthropological activities. The nitrate pollution of groundwater caused by agricultural activity and a substantial increase in fertilizer utilization are also becoming an increasing problem. Groundwater vulnerability mapping is an important key to improving planning and decision-making processes in order to prevent groundwater contamination Recognizing and zoning the vulnerable parts of the aquifer is an appropriate management tool for preventing groundwater pollution. In this study, Loor basin in Andimeshk located in the north west of Khuzestan province was selected as the study area. The main objective of this study is to assess the vulnerability of Loor basin aquifer to pollution using GODS model. The GODS model uses four parameters (groundwater confinement, overlying strata, depth of groundwater, and soil media) to evaluate aquifer vulnerability. At first, the layers of four parameters were prepared in GIS environment using ArcGIS 10. In the end, the vulnerability map of the region was produced with overlaying hydrogeological data. Verification of vulnerability assessments can be done in many different ways. The most common approach, particularly for verification of assessments done with overlay and index methods, is to compare the vulnerability map with the actual occurrence of some common pollutant in groundwater. Typical pollutants used are nitrate and pesticides. For validation GODS model in this study, nitrate concentration was selected as the primary contamination parameter. Forty six wells were selected for sampling and analysis. The accuracy of model was evaluated using observations values of nitrate and estimated vulnerability to pollution in the measured wells.