Hydrograph Analysis for Groundwater Recharge in the Phreatic Basement Aquifer of the Opeki River Basin, Southwestern Nigeria
Abstract
Using hydrograph analysis, the estimation of groundwater recharge to the phreatic basement aquifer of the Opeki drainage basin in southwestern Nigeria, with an approximate land area of 980 km2, indicates an annual value of between 29.23 x 106 m3 and 259.09 x 106 m3 , with an average of 134.45 x 106 m3 (i.e.137 mm). The recharge is between 3 and 20% of the total annual precipitation and the baseflow ranges from 6 - 47% of the total annual stream flow with a mean annual runoff (MAR) of 708 mm. The dependence of baseflow on the amount of groundwater recharge is evidenced by a high correlation coefficient of 0.98 and the positive influence of precipitation on baseflow and groundwater recharge, are provided by correlation coefficients of 0.6 and 0.7 respectively. The significant amount of recharge in the study area provides evidence of the considerable amount of groundwater in storage in the basement areas of southwestern Nigeria and on which effective water resources planning and development can be based.
References
Freeze, R.A., Cherry, J.A., 1979. Groundwater, Prentice-Hall Inc., 604 p.
Gauff Consultants (Nig) Ltd., 1995. National Water Rehabilitation Project, Zone D, Hydrological Report, Federal Ministry of Water Resources, 46 pp.
Goni, I.B. 2006. The challenges of meeting domestic water supply in Nigeria. Journal of Mining and Geology 42(1), pp. 51-55.
Goni, I.B., Travi, Y., Edmunds, W.M., 2005. Estimating groundwater recharge from modelling unsaturated zone chloride profiles in the Nigerian sector of the Chad Basin. Journal of Mining and Geology 41 (1), pp. 123 – 130.
Horton, R.E., 1932. Drainage basin characteristics, Trans. Am. Geophs. Union, Vol. 13, pp. 350-361.
Jones, H.A., Hockey, R.D., 1964. The geology of parts of southwestern Nigeria. Geol. Surv. Nig. Bull. 101 p
Korkmaz, N., 1990. The estimation of groundwater recharge from hydrographs, Hydrological Sciences, 35, 2, pp. 209-217.
Linsley, R.K., Kohler, M.A., Paulhus, J. L. H.,1982. Hydrology for Engineers, 3rd Edition, Mcgraw-Hill Inc. 482 p.
Ogunkoya, O.O., 2000. Water balance of a small catchment with permeable soils in Ile-Ife area, southwestern Nigeria, Journal of Mining and Geology 36 (1) pp.105-111
Sjodin, A., Lewis Jnr., W.A., Saunders III, J.F., 2001. Analysis of groundwater exchange for a large plains river in Colorado (USA), Hydrological Processes 15, pp. 609 -620.
UNESCO, 1972. Groundwater studies: An International Guide for Research and Practise. Edited by: Brown, R. H., Konoplyantsev, A. A., Inesson, J. and Kovalevsky, V. S.
Watson, I., Burnett, A.D., 1995. Hydrology, An Environmental Approach, CRC Press Inc. 702 pp.World Meteorological Organisation, 1974. Guide to Hydrological Practises, Third Edition, W. M. O. No. 168.
