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Experimental and numerical study of scour downstream Toachi Dam

Abstract:

The study analyzes the expected changes in the Toachi River (Ecuador) as a result of the construction of the Toachi Dam (owned by CELEC EP Hidrotoapi). Toachi is a concrete dam with a maximum height of 59m to the foundations. The top level is located at an altitude of 973.00 meters above sea level.With normal maximum water level located at 970.00 m, the reservoir has a length of 1.30 km in the Sarapullo River and 3.20 km in the Toachi River. The dam has a free surface weir controlled by two radial gates. It consists in 2 channels located in center of the dam that end in ski jump. The discharge is controlled by radial gates in order to ensure the accurate operation in the event when the gates are partially open. The spillway has been designed to spill up to a rate flow of 1213m3/s. It is necessary to know the shape and dimensions of the scour generated downstream of the dam. This scour is studied with four complementary procedures: laboratory model with 1:50 Froude scale similitude, empirical formulae obtained in models and prototypes, semi-empirical methodology based on pressure fluctuations-erodibility index, and Computational Fluid Dynamics (CFD) simulations.