Assessment of groundwater quality with ordinary kriging, empirical Bayesian kriging and radial basis function spatial interpolation techniques: Case study of Asaba

Groundwater stands as a primary source of drinking water in Asaba coastal region with significant influence on human health and ecological system. Hence, evaluating its quality is of paramount importance. This study investigates the spatial variability of groundwater quality in Asaba region and aim to predict conditions at unsample locations. To actualize this, physiochemical parameters and some selected heavy metals were analyzed from 62 water sampling locations. The parameters measured include Total Suspended Solids, Temperature, Acidity, as CaCO3, Alkalinity, as CaCO3, Magnesium, Lead (Pb), Nickel (Ni), and Zinc (Zn). This results were then compared against the World Health Organization permissible limits for drinking water. Descriptive statistical measures including Shapiro-Wilk test to confirmed normality satisfying the distributional requirement for Ordinary Kriging without data transformation were applied to evaluate the distribution of groundwater quality parameters. To predict values at unsampled location in the study area, empirical Bayesian kriging (EBK), Ordinary kriging (OK) and Radial basis functions (RBFs) were employed. The experimental variogram parameters were estimated using OK approach resulting in spherical model. Cross-validation statistics were then used to assess the performance of OK technique. Finally spatial distribution maps of groundwater quality were generated using EBK, OK and RBF categorized into five distinct of various classes.