Spatial variability and hydrogeochemical characterisation of groundwaters in Larkana of Sindh, Pakistan

Abstract

The current study examined the groundwater quality of different sampling stations of Larkana taluka based on GIS map using the interpolation method (IDW). The IDW method was applied in ArcGIS 10.5 software. Thirty representative groundwater samples were collected, mostly used for drinking purposes and examined for 24 different parameters. The water quality index (WQI) showed that 20.0% of samples were of poor water quality. The groundwater chemistry estimated from scatter diagrams showed weathering processes occurred in the study area. The silicate, carbonate, gypsum, farward ion exchange and reverse ion exchange were major weathering processes dominated in aquifer of study area. The land use may also be affecting groundwater chemistry. The samples were examined for coefficient of correlation (r), piper hydrochemical faces, Gibbs diagram, Chadha diagram and principal components analysis. EC, TDS, Cl, TH, alkalinity, Na, SO4, Ca, K and Mg were positively correlated to each other and indicated a similar geological origin. Total dissolved solids were observed 209–1642 mg/L and 76.71% samples were within permissible limit of 1000 mg/L. The results of nitrate, nitrite, orthophosphate, and total phosphate were within limits. The results of Pb 26.67%, Cr 16.67%, Cd 23.33%, and Ni 20.0% crossed the permissible limits of WHO for drinking purposes. The groundwater was examined for suitability for irrigation and 90–100% samples were indicated suitable for irrigation.