Performance of Flushing Efficiency of Sediment Evacuation from Wlingi and Lodoyo Reservoirs

The sediment evacuation from the reservoir should be carried out when it disturbs the dam development's functional design. There are issues regarding the objection to releasing sediment from the reservoir, especially related to potential environmental degradation of the river downstream. The sediment source entering the reservoirs is considerably variable, depending upon the catchment characteristics and the hydrological triggers. When limiting the erosion yield and controlling the sediment in the catchment, evacuating sediment from the reservoir could be the only alternative to avoid environmental degradation. Several issues showed that sediment evacuation from reservoirs is a cost-effective solution. Therefore, assessing the efficiency of sediment evacuation from a reservoir through flushing has become of high interest. This paper presents the analysis of the flushing efficiency performance of the flushing operation of Wlingi and Lodoyo Reservoir that was carried out on 10-17 March 2019. The flushing efficiencies are found to be 0.005 and 0.003 for Wlingi and Lodoyo Reservoirs, respectively. These figures are lower than that of Mrica Reservoir and other world reservoirs at higher than 0.1. Further analysis suggests the critical timing of the sediment evacuation schedule considering the inflow condition.