The limiting factor relationship between geoelectric and hydraulic parameters – a case study

Abstract

The limiting factor relationship between geoelectric and hydraulic parameters of parts of the West Chad Basin, northeastern Nigeria was appraised in this present study. The objectives of study included the estimation of the aquifer hydraulic parameters of the Pleistocene aged alluvium Formation from both the geoelectric and pumping test datasets with a view to determining empirical and limiting factor relationships and groundwater conditions. 106 geoelectric sounding and seventeen pumping test datasets were analyzed with RESIST Software and time – drawdown plots respectively. The concept of Dar-Zarrouk parameters was used to determine aquifer hydraulic parameters. The range of values from results included the following; derived transmissivity T_c (188.9-2789.8 m²/day) with T_c mean of 1540.84 m²/day; and field pumping transmissivity T (113.2 - 1436.6 m²/day with T_mean of 634.96 m²/day and derived hydraulic conductivity K_c values of 11.12-189.73 m/day, field pumping hydraulic conductivity K of 6.67- 101.31 m/day with the K_c mean of 115.34 m/day; K_mean of 36.22 m/day respectively. A linear fit relationship between the two datasets showed a correlation coefficient of 0.52861, standard deviation of 310.81. Higher values obtained from the geoelectric derived hydraulic parameters in few borehole sites in multiple of two or three suggested a limiting factor of the method. It may, therefore, be concluded that the limiting factor may have arisen from overestimation of the aquifer thickness occasioned by the degree of saturation and/or sand to clay ratio to which geoelectrical resistivity method might have responded. Hence, the method remained a tool on the choice of prospective high yielding borehole site selection from the consideration of the findings.

Keywords: Aquifer, hydraulic, geoelectric, pumping, transmissivity, saturation