Combined geophysical and hydrological study on climatic factors variability and their effect on aquifer productivity and recharge in Obubra, Cross River state

Abstract

Combined techniques of geophysics, hydrology and hydrogeology were employed in the estimation of groundwater recharge. Effects of meteorological factors on groundwater recharge were critically explored. Using tritium tagging and electrical resistivity techniques groundwater recharge was estimated. VES data was obtained from 16 stations, each with a traverse length of 500 m and inter station distance of 800m. Both the wet and dry season saw the completion of Tritium tagging surveys at every site. The study also looked at how weather conditions effected the stations aquifers productivity and recharge. The study found that rising rainfall causes an increase in groundwater recharge. The episodic variations in rainfall during period match with the patterns of groundwater recharge variation (1988-2018). The study also revealed a positive association between rainfall and groundwater recharge with a correlation coefficient of 0.9 but a negative correlation between groundwater recharge, temperature and evaporation with correlation coefficients of -0.52 and -0.42. But when the three climatic variables were combined with groundwater, the regression analysis revealed a multiple coefficient of determination of 0.821 percent (R²= 82.1 percent). Tritium tagging technique show that the recharge estimate in the study area varies between 6 and 19 percent. The study also revealed a linear relationship between electrical resistivity of the top soil and the estimated recharge.