Hydrogeologic and hydrochemical framework of the shallow groundwater system in the southern Voltaian Sedimentary Basin, Ghana |
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| Authors: | Stephen Y Acheampong John W Hess |
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| Institution: | (1) Graduate Program of Hydrologic Sciences, University of Nevada-Reno and the Water Resources Center, Desert Research Institute, University and Community College System of Nevada, P.O. Box 60220, Reno, NV 89506, USA, US;(2) Water Resources Center, Desert Research Institute, University and Community College System of Nevada, P.O. Box 19040, Las Vegas, NV 89132, USA Fax: +1-702-895-0496 e-mail: jack@dri.edu, US |
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| Abstract: | The southern Voltaian Sedimentary Basin underlies an area of about 5000 km2 in east-central Ghana. Groundwater in the basin occurs in fractures in highly consolidated siliciclastic aquifers overlain
by a thin unsaturated zone. Aquifer parameters were evaluated from available aquifer-test data on 28 shallow wells in the
basin. Hydraulic-conductivity values range from 0.04–3.6 m/d and are about two orders of magnitude greater than the hydraulic
conductivity calculated using Darcy's Law and the average groundwater velocity estimated from carbon-14 dating. Linear-regression
analysis of the transmissivity and specific-capacity data allowed the establishment of an empirical relationship between log
transmissivity and log specific capacity for the underlying aquifers.
Groundwater chemistry in the basin is controlled by the weathering of albitic plagioclase feldspar. The weathering rates of
various minerals were estimated using 14C-derived average velocity in the basin. The weathering rate of albite was calculated to be 2.16 μmol L–1 yr–1 with the resulting formation of 3.3 μmol L–1 yr–1 of kaolinite and 0.047 μmol L–1 yr–1 of calcite. The low porosity and permeability of the aquifers in the basin are attributed to the precipitation of secondary
minerals on fracture surfaces and interlayer pore spaces.
Received, September 1997 Revised, July 1998, August 1998 Accepted, August 1998 |
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| Keywords: | Ghana general hydogeology hydrochemistry sedimentary rocks |
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