Assessment of aquifer intrinsic vulnerability using GIS based Drastic model in Sialkot area, Pakistan

Abstract

The intrinsic vulnerability of a shallow aquifer of Sialkot is assessed using DRASTIC index method. The information required as input for all seven parameters, i.e. depth to water table, net recharge, aquifer media, soil media, topography, the impact of vadose zone and hydraulic conductivity data were collected from literature surveys and on field surveys. A cumulative vulnerability map was developed using the indices obtained as a result of DRASTIC methodology. The values obtained from DRASTIC model for the study area were between 112 and 151. The area was dominated by medium and moderate vulnerable zones covering an area of 446 km2 and 442 km2 respectively. An area of 79 km2 was covered by the low vulnerable zone while the high vulnerable zone encompassed a total area of 38 km2. Least covered area i-e., 09 km2 was found in the vicinity of the very high vulnerable zone. The validation of the DRASTIC model using the nitrate distribution revealed that very high and high indices have the lower percentage of reliability than of the low to moderate zones as compared with the nitrate distribution in the groundwater.