Evaluation of drinking water quality using the water quality index (WQI), the synthetic pollution index (SPI) and geospatial tools in Thatta district, Pakistan

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.