Assessment of ground water vulnerability in selected districts of Bangladesh using drastic index

Abstract

Around 75% of population of Bangladesh relies on groundwater for potable supplies and it is also extensively usedfor irrigation purpose during the dry season.Therefore, pollution of groundwater is a crucial issue. In this study, the pollution potential of three districtsof Bangladesh in Pabna, Sirajganj and Natore has been determined using DRASTIC indices.DRASTIC is a methodology that systematically evaluates the pollution potential of groundwater of an area. DRASTIC is acronym of depth to ground water, net recharge, aquifer media, soil media, topography, impact of vadose zone and hydraulic conductivity. It is then combined with weights and ratings to produce drastic index value. As the objective of the study was to determine the temporal variation of vulnerability of groundwater pollution ofPabna, Sirajganj and Natore district by DRASTIC index. Vulnerability of groundwater was determined for three seasons that is pre-monsoon, monsoon and post-monsoon periodsconsist of March to May, June to October, November to February respectively. For pre-monsoon period The DRASTIC index value range for Pabna, Sirajganjand Natore districts are83-109, 83-105 and 105-141respectively which indicates that Pabna has very low to low vulnerability,Sirajganjfalls under the same categoryand Natore district shows low to moderate vulnerability. For monsoon period The DRASTIC index value range for Pabna, Sirajganj and Natore districts are113-147, 121-146 and 123-141 respectively which indicates that Pabnaand Sirajganjfalls under the same categorylow to moderate vulnerabilityand Natore district also shows the same results. For post-monsoon period The DRASTIC index value range for Pabna, Sirajganj and Natore districts are113-135, 113-135 and 93-113 respectively which indicates that Pabnaand Sirajganjfalls under low to moderate vulnerability and Natore district falls under very low to low vulnerable areas. The objectivewas also to determine which parts of the areasare more vulnerable than other. From the study it is also found that in these three districts there is urban area where pollution potential is very low due to covered soil surface as waste materials cannot seep through it. It is hoped that this study will be helpful in future development and land use planning of this area and also assist in prioritizing protection, monitoring and cleanup efforts.