Empirical Estimation of Groundwater Recharge in Parts of the Basement Complex of Northern Nigeria
Knowledge of recharge estimates is essential to the sustainable development and management of groundwater resources. In this study two empirical methods were employed in estimating of groundwater recharge in Gusau and Bauchi in semi-arid Northern Nigeria. The recharge estimates were based on the methods developed by Sinha and Sharma (1988) and Turc (1954).Variability of annual rainfall and recharge estimates were determined using the coefficient of variation, while the equality of variance of recharge estimates obtained from the empirical methods were determined using Levnne’s Test. Simple Linear Regression was used to predict the mean groundwater recharge for thestudy period. Results of groundwater recharge for Bauchi based on the method developed by Sinha and Sharma gave a maximum and minimum estimate of 262.64mm and 158.50mm, while the highest and lowest estimate for Gusau was 252.49mm and 142.29mm. Highest and lowest annual average recharge estimate based on Turc’s method was, 687.49mm and 170.13mm for Bauchi, while the maximum and minimum estimate for Gusau was 578.76mm and 69.52mm. The results of the coefficient of variation shows a high level of variability based on Turc’s method, and a moderate degree of variability based on Sinha and Sharma’s method. The results of Levene’s Test indicated that variance of recharge estimates obtained from both methods differ significantly from each other. Regression model for the two locations revealed that rainfall generally accounts for more than 90 percent of groundwater recharge variation. The study recommended that scientific and periodic assessments of groundwater resources potential should be embarked upon.