Groundwater recharge estimation using chloride mass balance: a case study of Nsukka local government area of Enugu State, Southeastern, Nigeria

Due to the unplanned growth of urbanization, industrialization and ever-growing population in Nsukka local government of Enugu State, the groundwater exploitations have increased dramatically. For proper planning and management of groundwater resources, there is need for a reliable estimate of groundwater recharge of the area. In the present study, for the first time, the chloride mass-balance method is adopted to estimate groundwater recharge in the study area. Measurements of chloride in groundwater and rainfall were made during 8-month period of the raining season beginning with the first rain on 5th March 2016 and the last rain on 10th October 2016. The main source of recharge considered was estimated from rainfall. The results are presented in the form of a map showing the spatial distribution recharge rate of the study area, which ranges from 1308.9 to 1683.3 mm/year and the recharge percentage of the total rainfall varies from 81.5 to 95.8%. The study area is characterized by moderate groundwater recharge due to the presence of high permeable underlying lithologies which associated with high porosity. Errors in the estimated recharge rate in work maybe large because of the limited data used in this analysis.