An Operational Sediment Flushing Scheme for the Ocaña hydropower plant Regulation Reservoir in Ecuador

The Ocaña hydropower plant in Ecuador has been affected by long shutdowns related to sediment accumulation in its regulation reservoir. The lack of sediment flushing strategies has caused the plant to operate, in several occasions, under severe sedimentation levels that greatly hinder the maintenance and cleaning of the reservoir. In that regard, a specific definition of how and when to evacuate the sediment is needed. Therefore, a process-based numerical model was implemented to reproduce the hydrodynamics and morphodynamics inside the structure, and evaluate different sediment flushing operations. The proposed schemes make use of the available gates and sluices that are already a part of the plant’s intake and regulation system infrastructure. Moreover, to determine the respective sedimentation rates and loss of storage volumes during continuous plant operation conditions, the morphological evolution of the bed was forecasted until the level of siltation reached its maximum. Results show that the most efficient sediment flushing strategy allows water to enter via the river intake while the reservoir is being emptied through the flushing gate. Additionally, the model shows that by carrying out periodic sediment flushing operations every 2 months, the need to perform complete cleanings of the structure would be limited to only twice a year, which would greatly enhance the power plant operation.

Keywords: hydropower; sedimentation; process-based numerical model; morphological evolution forecast, sediment flushing.