Articles | Volume 377
Proc. IAHS, 377, 57–66, 2018
Proc. IAHS, 377, 57–66, 2018

  16 Apr 2018

16 Apr 2018

Sedimentation and Its Impacts/Effects on River System and Reservoir Water Quality: case Study of Mazowe Catchment, Zimbabwe

Colleta Tundu1, Michael James Tumbare2, and Jean-Marie Kileshye Onema3 Colleta Tundu et al.
  • 1Zimbabwe National Water Authority, P.O. Box Cy617 Causeway, Harare, Zimbabwe
  • 2Department of Civil Engineering, University of Zimbabwe, P.O. Box MP167, Mt Pleasant, Harare, Zimbabwe
  • 3WaterNet Secretariat, P.O. Box MP600, Mount Pleasant, Harare, Zimbabwe

Abstract. Sediment delivery into water sources and bodies results in the reduction of water quantity and quality, increasing costs of water purification whilst reducing the available water for various other uses. The paper gives an analysis of sedimentation in one of Zimbabwe's seven rivers, the Mazowe Catchment, and its impact on water quality. The Revised Universal Soil Loss Equation (RUSLE) model was used to compute soil lost from the catchment as a result of soil erosion. The model was used in conjunction with GIS remotely sensed data and limited ground observations. The estimated annual soil loss in the catchment indicates soil loss ranging from 0 to 65 t ha yr−1. Bathymetric survey at Chimhanda Dam showed that the capacity of the dam had reduced by 39 % as a result of sedimentation and the annual sediment deposition into Chimhanda Dam was estimated to be 330 t with a specific yield of 226 t km−2 yr−1. Relationship between selected water quality parameters, TSS, DO, NO3, pH, TDS, turbidity and sediment yield for selected water sampling points and Chimhanda Dam was analyzed. It was established that there is a strong positive relationship between the sediment yield and the water quality parameters. Sediment yield showed high positive correlation with turbidity (0.63) and TDS (0.64). Water quality data from Chimhanda treatment plant water works revealed that the quality of water is deteriorating as a result of increase in sediment accumulation in the dam. The study concluded that sedimentation can affect the water quality of water sources.

Short summary
Soil erosion result in the deposition of sediments into rivers and reservoirs. The sediments affect the water quality resulting in the treatment of the water being expensive. The sediments that are carried into the reservoir reduces the capacity of the dam. The reduction of water quality in Chimhanda dam as well as the increase in the cost of treatment of the water pushed the author to do a research.