Groundwater vulnerability assessment to pollution using GIS-based DRASTIC and GOD methods in Araihazar upazila of Narayanganj district, Bangladesh

A groundwater vulnerability map is a preliminary way to assess the risk of groundwater pollution from a variety of sources and across a range of geological and hydrological contexts. With rapid urbanization and industriali-zation, the possibility of groundwater contamination has greatly increased in Bangladesh. The focus of this study is on an industrialized peri-urban area in Bangladesh, where the regional aquifer has already been depressurized owing to pumping to fulfill the ascending municipal and industrial water demand of the Dhaka megacity and adjacent areas. Two vulnerability index maps were created utilizing a Geographic Information System (GIS) and the contamination risk indices DRASTIC (Depth to water table (D), Net recharge (R), Aquifer media (A), Soil media (S), Topography (T), Impact of vadose zone (I) and hydraulic Conductivity of the aquifer (C)) and GOD (Groundwater or hydraulic confinement in the aquifer under consideration (G), Overlying strata in terms of lithological characters that determine the pollutant attenuation capacity (O) and Depth to groundwater (D)). Vulnerabilities varied greatly over the study area. The DRASTIC analysis identified three vulnerability classes: one-fifth of the area exhibited high vulnerability, more than half of the study area showed moderate vulnerability and rest of the area is low in vulnerability. In contrast, GOD analysis was somewhat conservative, showed two classes where vulnerability was negligible in 58% of the study area and low in the rest of the area. The study also generated hot-spot maps of potential surface contamination for each vulnerability map by overlapping the potentially hazardous activity layer which corresponds to areas with higher industrial clusters. Human activities that commonly cause groundwater pollution need to be constrained by utilizing groundwater protection stra-tegies in the identified vulnerable areas to ensure sustainable development.