Assessing groundwater vulnerability in Ramhormoz aquifer using a GIS and DRASTIC Techniques

Aquifer vulnerability assessment to identify areas that have a potential contamination of water re-sources management, is very important. One of the rudimentary and important ways to prevent groundwater contamination is the identification of vulnerable areas and applied its results for land use management. In this study, the vulnerability of Ramhormoz aquifer evaluated by an Analytic hierarchy process (AHP) method and Modified DRASTIC based on GIS. In the DRASTIC model the map of seven hydrogeological characteristics affecting groundwater pollution (depth to water, net recharge, aquifer media, soil type, topography, the impact of vadose zone and hydraulic conduc-tivity) was combined using Geographic information system (GIS) and aquifer vulnerability map was prepared. In order to overlaying the data layer tree methods (DRASTIC-DRASTIC, DRASTIC-AHP and AHP-AHP methods) have been used. Nitrate concentration data of groundwater have been used for model validation. The results show that, except the southeast that have a high vulnerability, other parts of plain have a low to moderate vulnerability. In the study area, DRASTIC-DRASTIC and DRASTIC-AHP methods have a better results rather than AHP-AHP method. The correlation coefficient between Q index and nitrate concentration in DRASTIC-DRASTIC, DRASTIC-AHP and AHP-AHP methods is obtained 0.97, 0.96 and 0.81, respectively, which confirmed the results.