Determination of vulnerability of aquifer Ardebil using DRASTIC method in GIS

Groundwater resources are the most valuable resources of each country. Development of agricultural activities in Ardabil plain and over-use of fertilizers and pesticides, improper disposal of municipal sewage and industrial areas are responsible for groundwater pollution. Clean-up of groundwater resources is very difficult and expensive. One of suitable method in preventing groundwater contamination is determination of the vulnerable zones of an aquifer to manage water resources and sustainable development. 

In this study for determining of vulnerability of aquifer Ardebil, information of 52 observational wells, 43 pumping tests, average of annual precipitation of 8 stations, 45 logs of exploration wells, land use map, topographic map and geological map have been gathered. Then, data layers of groundwater depth (D), Recharge (R), Aquifer media (A), Soil media (S), topography (T), impact of vadose zone (I) and hydraulic conductivity of aquifer (C) were prepared and overlaid based on DRASTIC method in ArcGIS software.

Zoning map of DRASTIC method showed that DRASTIC index varied between 63 to 195 units. Areas with high vulnerability potential were characteristic with shallow depth groundwater, coarse-texture soil, thin soil and gentle topographic slope. Accuracy of the zoning map was evaluated by nitrate concentration map which showed the increase of DRASTIC index with nitrate concentration.

Northwestern and central parts of the Ardabil plain showed high vulnerability. The results of this study could help to reduce the environmental impact of contaminants on groundwater resources of the study area in future.