Understanding sediment process in the Magoye reservoir of Southrn Province Zambia

Abstract

Reservoir sedimentation is one of the problems facing managers of small reservoirs (with ≤5m height of embankment). The main methods used to understand sedimentation process in the Makoye reservoir included sediment coring, onsite measurements using Sedimeter SM3A, use of Elevation Change Method (EMC), laboratory analysis of sediment core, 3D Spatial Analyst Tools (3DSATs) in ArcGIS 10.3 as well as mathematical models. The reservoir had been silting at a significant rate of 3,112.97 m3 yr-1 leading to average accumulation of 87,163 m3 of sediment, which had eventually reduced the reservoir's storage capacity by 53.5%. The EMC methods also revealed that Makoye reservoir tapped 79,749.38 m3 of sediment giving rise to the between method average sediment volume of 83,456.26 m3. Reservoir's useful life was found to be 24 years. Results from Sedimeter SM3A showed that a total depth of 0.688cm of sediment had accumulated during a period of 309 hours in the 2015/2016 rainy season as compared to 1.56 cm in the 2016/2017 rainy season. The long term average depth of sediment was found to be 2.4 cm. It was concluded that sedimentation in the Makoye Reservoir is a serious problem which may lead to complete loss of reservoir storage capacity.