Estimation of Reservoir Capacity and Sedimentation Rate Using Direct and Indirect Methods

Abstract

Dams are important in harnessing flood water to enhance water availability during the dry season. Globally, most dams no longer hold the amount of water they were designed to hold due to sedimentation. The study sought to monitor sedimentation of Chesa dam in Upper Ruya Subcatchment, Mazowe Catchment in Zimbabwe. Five Landsat 8 OLI datasets for the period 2015 to 2017 were used. Remotely sensed sedimentation data was analysed using the NDWI method. Results indicated that Chesa dam's current capacity was 374,535 m3 against the design capacity of 1,150,000 m3 in 1991, indicating a loss of 775,465 m3. The annual rate of sedimentation for Chesa was estimated to be 2.7% and this suggests that the dam might completely sediment by year 2028. The difference between observed and predicted sedimentation rate was 0.36% indicating that remote sensing can be used for reservoir capacity estimation. It was concluded that there is rapid environmental degradation upstream hence the high rates of sedimentation. There is need for drastic interventions to enhance sustainable landuse practices upstream of the dam. The study confirmed that remotely sensed data and GIS technology can be used in determining reservoir capacity. Future studies may need to use finer resolution data for similar studies.