4 th International Conference on Water & Flood Management (ICWFM-2013) 337 DRASTIC-BASED VULNERABILITY ASSESSMENT OF BARIND TRACT AQUIFER IN NORTHWESTERN BANGLADESH Sajal K Adhikary 1* , A.B.M. Irad Hossain 1 , Mukand S Babel 2 and Ashim Das Gupta 2 1 Department of Civil Engineering, Khulna University of Engineering & Technology, Khulna-9203, Bangladesh, e-mail: sajaladhikary@yahoo.com, abmih002@yahoo.com 2 Water Engineering and Management Division, Asian Institute of Technology (AIT), Pathumthani-12120, Thailand, e-mail: msbabel@ait.ac.th, ashim.dasgupta@gmail.com ABSTRACT Barind Tract, largest Pleistocene physiographic unit of the Bengal Basin, recognized as a unit of Old Alluvium, which differs from the surrounding floodplains. The aquifer is the main source of water supply in the vicinity and is showing signs of contamination due to the existence of pollution sources and the treatment of aquifer is quite impossible and impractical. Regional assessment of groundwater (GW) pollution risk is a useful tool for successful management of GW resource and its protection. In this study, the index-based DRASTIC method is adopted to evaluate aquifer vulnerability to potential pollution, including seven parameters such as water table Depth, Recharge, Aquifer media, Soil media, Topography, Impact of the vadose zone and hydraulic Conductivity. Determination of the DRASTIC index involves multiplying each parameter weight by its site rating and summing up the total. The Barind Tract aquifer located in three northwestern districts (Rajshahi, Naogaon, Chapai Nawabganj) of Bangladesh have been considered in this study. Necessary data related to each parameters of DRASTIC are collected. Based on estimated DRASTIC index values, a GW vulnerability map is established in the framework of ArcGIS platform. The higher index values symbolize greater potential for GW pollution, or greater aquifer vulnerability. The results provide valuable information and the pollution risk map can be useful to local authorities and decision makers for successful GW resource management and protection zoning. The result demonstrates that 63% of the total study area (4700 sq. km.) is highly vulnerable and only 8% of the study area (579 sq. km.) is located within the low vulnerable domain. The study conclusively proves that the Barind Tract aquifer in the northwest region of Bangladesh is highly vulnerable to potential GW pollution due to unplanned activities practiced in the study area. Keywords: Aquifer, ArcGIS, barind tract, DRASTIC, groundwater pollution, vulnerability 1. INTRODUCTION Growing trend of anthropogenic stresses on groundwater (GW) resource, especially impacts of extensive land use leads to increase in the GW pollution and contamination. Therefore, improvement of tools and techniques are essential for identifying and preventing the potential contamination of GW resources in order to use GW safely without threats of depletion and pollution. In such case, vulnerability assessment of GW resources can be useful because it can provide preliminary information and criteria for decision-making (Ranjan et al., 2007). In Bangladesh, contamination of GW due to increased use of fertilizers and pesticides along with various anthropogenic activities is an ever-increasing problem. Therefore, more attention should be paid to the probable impacts of irrigated agriculture and other human interventions on GW quality. The Barind area in the northwestern Bangladesh is one of the most important agricultural