Spatial statistical analysis of groundwater quality based on inverse distance weighting and ordinary kriging in District Sheikhupura, Pakistan

Groundwater is an important source of fresh drinking water in Pakistan and it has a great impact on human and ecological health. Therefore, it is imperative to evaluate the quality of groundwater. This study aims to explore the spatial variability of groundwater quality and to predict the unmeasured locations in Sheikhupura, Pakistan. For this purpose, hydro-chemical results of 105 water samples were taken from the Pakistan Council of Research in Water Resources (PCRWR). The water quality parameters including total dissolved solids, calcium (Ca), magnesium (Mg), hardness, sodium (Na) and sulfate (SO4) were measured from each sample at every location and compared with the permissible limits of the World Health Organization (WHO). Initially, descriptive statistical measures along with normality tests are carried out to assess the shape of water quality parameters. Later on, two geostatistical prediction techniques: inverse distance weighting (IDW) and ordinary kriging (OK) were considered to predict the unmeasured locations within the study domain. In this case, the parameters of the experimental variogram (sill, range and nugget) were estimated using the best-fitted variogram models including exponential, spherical, matern and Gaussian. Cross-validation statistics were carried out to evaluate the performance of IDW and OK. Results showed that the OK better performed than IDW. Furthermore, the water quality index was plotted to demonstrate the overall quality of groundwater in District Sheikhupura. It was observed that the area (South-West) with latitude 31.55°–31.66° and longitude 73.79°–73.93° have a very poor quality of groundwater. On the whole, only 9.6% of locations have excellent water for drinking. Thus results showed that the quality of groundwater is not satisfactory in Sheikhupura, Pakistan; therefore, serious preventive measures are required to reduce possible threats to human and ecological health.