Groundwater vulnerability assessment in Khulna district of Bangladesh by integrating fuzzy algorithm and DRASTIC (DRASTIC-L) model

Effective groundwater resource management is now a critical issue because of climatic change, especially in areas, where agricultural and industrial activities require a huge volume of water. Due to climate change and accelerated sea level rise, groundwater quality of coastal Khulna district is decreasing day by day. This study aimed at integrating fuzzy AHP method and a modified DRASTIC (DRASTIC-L) model for assessing groundwater vulnerability. The DRASTIC-L factors, including Depth of water, Net recharge, Aquifer media, Soil media, Topography, Impact of the vadose zone, Hydraulic conductivity and Land use land cover were used to examine the spatial distribution of groundwater vulnerability in Khulna District. After employing fuzzy algorithm supported DRASTIC-L model, the results showed that about 18.93% (307.12032 km2) area in Khulna is highly vulnerable in terms of groundwater quality. On the other hand, groundwater in 10.06% (163.21344  km2) and 24.85% (403.1664  km2) of the area are very low to low vulnerable. Though the validation of groundwater vulnerability assessment is a complicated process; still accuracy of the research was assessed by performing a correlation between groundwater vulnerability index and two groundwater quality parameters, Chlorine (Cl) concentration and electrical conductivity (EC) in the study area. Both EC and Chlorine (Cl) concentration appears to have positive correlation—R2 = 0.46, and R2 = 0.44 with the groundwater vulnerability index of DRASTIC-L model. Targeted interventions are needed to arrest the increasing trend of groundwater vulnerability in areas of Khulna, where natural resource-based livelihood and food security are already in severe threat. Therefore, the findings of the research could help the responsible authorities and decision-makers to take prudent measures for limiting factors that trigger the level of groundwater vulnerability in the coastal landscape of Khulna.