Spatial dependency of groundwater quality in Benin City, Edo State, Nigeria using semi-variogram models

Abstract

Water quality is a worldwide concern especially water for human consumption. Regular monitoring and tools should be developed, to ensure continuous assessment of the level of concentration of chemical constituents prevalent in water. This will guide against health dangers and risks associated with water of low quality. The research focus on using semi-variogram models to measure the degree of spatial dependency of sampled boreholes for prediction of the concentration of water quality parameters at un-sampled locations because of the cumbersome nature of assessing the whole boreholes in Benin City. One hundred and ten (110) different domestic boreholes were systematically sampled and analyzed in laboratory for determination of the concentration of some chemical water quality parameters which include Electrical Conductivity (EC), Total Dissolve Solids (TDS), Bicarbonate (HCO3), Sodium (Na), Potassium (K), Calcium (Ca), Magnesium (Mg), etc. Laboratory examination of boreholes water quality parameters were carried out in wet and dry seasons. Geographical locations of sampled boreholes were also determined. The obtained experimental results were utilized in investigating the spatial structure of the boreholes using semi-variogram models which include spherical, exponential, Gaussian etc. Exponential model was the most fitted model. The borehole water quality parameters exhibited high degree of spatial dependency in EC, TDS, HCO3, Na, K, Ca. Mg, Cl, P, and NO3 in both seasons with ratio < 25% therefore, interpolation technique can be employed to produce spatial variation quality map of boreholes in Benin City as a monitoring technique to detect contamination or changes in water quality.