Environmentally-suspended sediment production of the Nasia River Basin, Northern Ghana

Abstract

Rivers constitute an important source of surface water supply for most sectors in the world. In areas with single rainfall maximum, as in the north of Ghana, the rivers are normally intermittent or ephemeral with only few perennial ones. The Nasia River Basin is the drainage basin of the left bank tributary of the White Volta within the Guinea Savannah Ecological Zone and lies in the Northern Region of Ghana. The study assessed the level of suspended sediment produced in the Nasia River Basin. Hydrological and meteorological data and water samples were used for the study. Average suspended sediment yield (33 years) in the basin was 19.90 t/km2/yr. With mean annual runoff of 439.13m3/s, 322.43 t/yr suspended sediment is discharged into the White Volta from the Nasia River. Mean suspended sediment concentration and turbidity values for three months of continuous study were 423.86 mg/l and 406.19 NTU respectively. The mean discharged suspended sediment of 0.13 kg/s, 0.25 kg/s and 1.31 kg/s were recorded for April, May and June 2007 respectively for the basin. These levels of suspended sediment deposited in the river bed reduce the carrying capacity of this water system. The study realised that catchment characteristics have a great influence on suspended sediment production in the Nasia River Basin. The reduction of the level of erosion and suspended sediment transport and deposition in the river bed is therefore very important.

KEY DESCRIPTORS: River Basin, Drainage System, Guinea Savannah, Suspended Sediment, Turbidity.