Groundwater Quality Mapping using Geographic Information System: A Case Study of District Thatta, Sindh

Access to safe and affordable drinking water for all is an important goal of SDGs (Sustainable Development Goals). Degradation of water quality of coastal aquifers is a major concern throughout the world including the Indus River delta. Looking at the present changing climate scenario, the study was conducted to assess and map the spatial variation in the groundwater quality of district Thatta using GIS (Geographic Information System). The groundwater samples from hundred (100) randomly selected hand pumps of the district were collected such that all union councils of the district were sampled. The water samples were analyzed for different physicochemical parameters, i.e. taste, color, odor, pH, turbidity, EC (Electrical Conductivity), calcium, magnesium, total hardness, chloride, total dissolved solids, and arsenic using standard laboratory techniques. The results of water analysis revealed that 85% of the groundwater samples had TDS (Total Dissolved Solids) concentration beyond the permissible limit described by WHO (World Health Organization). Whereas, all the groundwater samples had chloride concentration beyond permissible limit of 250 mg/l. Analysis for arsenic revealed that only 20% of groundwater samples had a concentration higher than the safe limit of 10 ppb. The study indicated that in most of the areas, the groundwater quality was not as per drinking standards prescribed by WHO, hence was not suitable for drinking purpose. The GIS maps of groundwater quality parameters were prepared using spatial interpolation Kriging tool. These maps provide the visual analysis and interpretation of spatial variability of different groundwater quality parameters, hence are supportive in monitoring and managing the vulnerability of groundwater contamination.