[01] Okonkwo Austin Chukwuemeka, Department of Geology and Mining, Enugu State University of Science and Technology, Enugu, Nigeria.

A re-appraisal of groundwater quality in some parts of Central Benue Trough had been carried out. Areas sampled are within the Lafia-Keana in the Central Benue Trough. Water wells in the area tap the shallow Lafia Formation which is made up of whitish to brownish, feldsparthic and ferroginized sandstone. Physic-chemical analyses indicate pH range (4.7 – 8.20) from acidic through neutral to moderate alkalinity. Total Dissolved Solids (TDS) values were high in most locations with their corresponding high electrical conductivity (EC). Total hardness (TH) shows that 75% of the groundwater is classified as very hard as a result of high calcium content. Piper Trilinear diagram show Calcium – Bicarbonate water type. High sulphate ion enrichment may be due to the ionic reaction from coaly formation underlying the area. Sodium Adsorption Ration (SAR) show excellent for irrigation purpose. Calcite saturation analysis shows that most of the wells are oversaturated with respect to calcite. Generally the groundwater in the study area is greatly impaired when compared with the WHO standard limits for drinking water. Possible ways of improving the groundwater quality are through aeration method and installing a workable water treatment plant.

Hydro Geochemistry, Sodium Absorption Ratio, Calcite Saturation index and Groundwater Quality

[01] Etu-Efeotor, J.O., 1981. Preliminary hydrogeochemical investigations of the sub-surface waters in parts of the Niger Delta. Journ. Min. Geol. Vol. 18. No. 1. P. 103 – 105. [02] Freeze, R.A. and Cherry, J.A., 1979. Groundwater. Prentice – Hall, Inc. New Jersey. [03] Houlsow, A.W., 1995. Water Quality: Data Analysis and interpretation. Lewis Publishers, Flordia. 386p. [04] Hein, J.D., 1970. Study and Interpretation of Chemical characteristics of natural waters. Water supply papers. Publication of U.S. Geological survey, Washington DC. No. 1473, p. 254 – 255. [05] Hein, J.D., 1989. Study and Interpretation of the Chemical Characteristics of natural waters. 4th Edition. U.S. Geol. Surv. Water – Supply paper 2254. [06] Knobel, L.L., and Philips, S.W., 1988. Aqueous geochemistry of the Magothy Aquifer, Maryland. U.S. Geol. Surv. Paper 2323. [07] Nwajide, C.S., 1990. Sedimentation and Paleogeography of the Central Benue Trough, Nigeria, in C.O. Ofoegbu, edition. The Benue Trough Structure and Evolution. Viewer Braunschwaig, p. 19 – 38. [08] Offodile, M.E., 1976. The Geology of the Middle Benue of Nigeria. University of Uppasala, Paleo. Inst., Special Vol. 4 p. 146 – 160. [09] Offodile, M.E. 2000. Groundwater Study and Development in Nigeria. Mecon Geology & Eng. Services Ltd. 453p. [10] Oteze, G.E., 1991. Portability of Groundwater from the Rima Group in the Sokoto Basin. Nigeria. Journ. Min. and Geology. Vol. 27. No. 1. p. 17 – 23. [11] Ojoh, K.A., 1992. The southern part of the Benue, Trough (Nigeria) cretaceous stratigraphy, Basin Analysis, Paleo-oceanography and geodynamic evaluation in the equatorial domain of the South Atlantic: NAPE Bulletin. Vol. 7. No. 2. p. 131 – 152. [12] Obaje, N.G., Ulu, O.K. and Petters, S.W., 1999. Biostratigraphic and geochemical controls of hydrogcarbon prospects in the Benue Trough and the Anambra Basin, Nigeria. NAPE Bulletin, Vol. 14. No. 1. p. 18 – 54. [13] Ozoko, D.C., 2004. Geochemical and Microbial Studies of the natural water system in Agila, Benue State, Nigeria. NAH water resources Jour. Vol. 15, No. 2. p. 60 – 64. [14] Petters, S.W. and Ekweozor, C.M., 1982. Origin of Mid-cretaceous black shales in the Benue Trough, Nigeria. Paleogeography, Paleoclimatology, Paleoecology, vol. 40, p. 311 – 319. [15] Stednick, J.D., 1991. Wildland Water Quality Sampling and Analysis. Academic Press Inc. San Daigo, 216p.`