A NUMERICAL FORMULA AND COST BENEFIT OF GROUNDWATER RECHARGE IN MAIDUGURI, NIGERIA

In this paper, relationship between rainfall and groundwater recharge (GR)  was established and evaluated with cost benefit. Rainfall measured in Maiduguri, Nigeria was used to fix the unknown constants of the numerical formula (NF) using Microsoft Excel Solver. The constants were used to establish NF. The NF was used to estimate GR from the rainfall. Accuracy of the NF was evaluated statistically (relative error; the degree of accuracy, numerical reliability, Model of Selection Criterion (MSC) and Akaike Information Criterion (AIC)) and compared with the formulae in use using field GR Uttar Pradesh (UP) method as the reference GR. A basic cost benefit of GR was conducted. The study revealed that GR using the current models were similar to GR using  UP, Chaturvedi, Kumar and Seethapathi and Rao, but different in magnitude of GR. NF provided the lowest relative error of 0.146 %, the highest MSC of 13.436; the degree of accuracy of 99. 854 % and the lowest AIC of 43.348 with Rao formula having   highest relative error of 56.56 %, the lowest MSC of  0.96; the degree of accuracy of  43.44 % and the lowest AIC of 1403.43. The present average cost benefit of groundwater recharge in Maiduguri was found to be 619.60US $ m-2Yr-1. It was concluded that GR using the numerical formula is a promising tool for GR with minimum error in water resources management.