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The objective of the present study was to evaluate the quality of groundwater in the deltaic region of the Indus River in district Thatta, Pakistan. In the region, the groundwater is widely used for drinking purposes. Due to excessive abstraction rates of groundwater, a significant amount of seawater intrudes into the aquifers. The situation is, furthermore aggravated by dwindling flows of freshwater from the river Indus. Thus, groundwater samples (100) were analyzed for different physicochemical parameters. A number of water quality parameters crossed the WHO guidelines. The WQI model revealed that 8%, 57%, 20%, and 15% of the samples were good, poor, very poor and unsuitable for drinking purposes, respectively. Likewise, the SPI model indicated that 10%, 55%, 19%, and 16% were slightly polluted, moderately polluted, highly polluted and unsuitable for drinking. Though the model's input is different, the proportionate of ranking revealed a significant correlation (R 2 = 0.78) between the outcomes of both models. The geospatial mapping of physicochemical parameters, WQI, and SPI model outcomes indicated that most of the groundwater resource in the study area is contaminated, thus not suitable for drinking purposes. The methodology developed in this study is extendable to other similar environments in the world.

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.

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