Sediment management at the water intake of hydropower plants

Dams interrupt the continuity of the mass transport through rivers and retain sediments, resulting in the loss of the reservoir capacity. This aims to design, implement, and evaluate alternatives for the mechanical dredging of the sediment near the water intakes. The sediment can threaten the structural stability of the dam and block the water intake, increasing operating costs and decreasing the income from the electricity generation. The slope of the sediment cone for different depth conditions of the water inlet was determined through bathymetric studies carried out for over more than 5 years. The maximum depth to be cleaned near the water intake and the sediment type are fundamental variables to select the dredging technique. The amphibious pontoon and the boom of the dragline were determined considering the maximum discharge distance that would allow the discharge to be made directly downstream of the dam. The slopes of the sediment bed were 15.5 to 26.8° in the direction of the riverbed and between 17.1 and 43.8° in the direction of the water inlet. The mechanical dredging with clamshell dredger or grab bucket overhead crane uses the more effective dredge techniques for great depths (low-level outlets) and dredge the material composed of sand, clay, and logs. The values of the slopes of the sedimentary beds were determined experimentally through bathymetric studies. These results allowed adjusting the prediction models of dredging and recovery of the reservoir’s storage capacity.