Analysis of recharge and groundwater flow in parts of a weathered aquifer system in Northern Ghana

Abstract

Stable isotope data were used to relate recent meteoric water to groundwater in parts of the Nabogo sub-catchment of the Voltaian Basin. Estimates of the rates of evaporation of recharging groundwater in transit were made on the basis of the stable isotope data. This study finds that groundwater recharge within the weathered zone aquifer system in the study area is of recent meteoric origin. There is, however, evidence of significant evaporation of recharging water in the range of 34–70%, as a result of high temperatures and low relative humidities. This high level of evaporation of rainwater prior to or in the process of recharge is attributed partly to slow infiltration due to significant clay content of the intervening material between the saturated zone and the surface. It suggests limited but variable fortunes in terms of groundwater recharge from precipitation in the area and ties in with previous findings in relation to groundwater recharge estimates. This justified the use of previous estimates of groundwater recharge in other parts of the terrain for the conceptualization of the groundwater flow through a numerical model under steady-state conditions. This study determines that the general groundwater flow is controlled by local flow systems with no obvious preferred direction of flow. Calibrated hydraulic conductivity estimates range between 0.35 and 5.14 m/d. This is consistent with the nature of the material of the aquifer, and will provide the basis for assessing the hydrogeological conditions of the weathered zone.

Keywords:

• Nabogo
• Voltaian Basin
• recharge
• isotopes
• hydraulic conductivity

Funding

This project was sponsored in its entirety by the University of Ghana Research Fund, through the Office of Research, Innovation, and Development, ORID, of the University of Ghana.

Notes on contributors

Dr Yidana is a Senior Lecturer of Hydrogeology and Geostatistics at the Department of Earth Science University of Ghana. His research is pioneering in some aspects of the hydrogeology and hydrochemistry of Ghana. With over 50 peer reviewed publications in international journals and media of significant impact. He supervises several students at the graduate level whilst serving on a number of key administrative boards at the University of Ghana. Dr Yidana is on the editorial boards of the Journal of African Earth Sciences (Elsevier), The Scientific World Journal (Hindawi Publishers), and the Legon Journal of Science and Technology.

Obed Fiifi Fynn is a graduate student under the supervision of Dr Yidana. He is undertaking an extensive study of groundwater recharge processes and the evolution of recharging water through the unsaturated zone in the northern parts of the Voltaian Sedimentary Aquifer System.

Dr Larry Pax Chegbeleh is a lecturer of hydrogeology and engineering geology at the Department of Earth Science, University of Ghana. He supervises several undergraduate and graduate students in his discipline and has been copiously cited by his peers in the international media.

Mrs Yvonne Loh is currently completing her Ph.D. thesis on groundwater hydrochemistry in the Bosomtwe and surrounding areas. She is using natural tracers to investigate the possible hydraulic relationship between surface water in the Lake and groundwater in the underlying aquifers in the area. Mrs Loh is a lecturer in hydrogeology at the Department of Earth Science.

Miss Millicent Obeng is a research student under the supervision of Dr Chegbeleh at the Department of Earth Science, University of Ghana. She is developing a numerical model to characterize the groundwater flow regime in parts of the White Volta basin.