Esmeralda Reservoir Sedimentation and Discharge Study

In hydro power generation applications, the primary function of reservoirs is to provide storage capacity. The most important aspect of this design is the analysis of the relation between sediment yield and storage capacity. If sediment inflow is large the reservoir capacity may be limited and the useful life of the reservoir shorten. Reservoir planning requires the correct consideration of the probable rate of sedimentation in order to foresee the actual life cycle of the structure and maintenance requirements. The main difficulty associated with reservoir sedimentation is the management and disposition of accumulated sediment. In the mountainous region of Colombia, sediment yield is important and has significantly affected the operations of the Esmeralda reservoir. Built in the 1960´s, the reservoir was designed considering estimated rate of sediment production and involved a system of sluice gates to provide for sediment discharge away from the tank. Lately the gate system has been ineffective and accumulation of sediments in the reservoir has impaired operations appreciably. It is believed that considerable changes in the watershed have altered the sediment transport dynamics, significantly reducing the efficiency and capacity of the tank. This study investigated the usefulness of various low-cost sediment extraction systems, based on the use of a siphon, for example through physical experimentation in laboratory. Also, a numerical flow model of the reservoir was examined in order to provide for a better understanding of the minimum flow velocities through the sluice gate system and density current within the tank. The study revealed that flow velocities are inappropriate to ensure the removal of the sediments currently observed within the tank and that the proposed siphon extraction system could provide for an innovative sediment control measure. It is thought that substantial changes in land use over the last 50 years has altered the sediment characteristics of the channel and rendered the design of the reservoir obsolete.