Reservoirs have to be operated in a way that increases the benefits of them and managing in the best feasible way risks inherent to its operations. In the case of Alto Anchicayá reservoir, the main objective is to generate energy in the most efficient way maximizing the annual economic profit of the asset. The challenge to achieve this optimization is the uncertainty on the long-term energy prices and the water inflows. These two variables have a stochastic process behavior with a moderate to high uncertain forecast: the first is the oscillation of the energy price (dependent on the demand and the available energy firm storage in the country power system) and the second is the natural variability of the water inflow, which has seasonality but has a strong random component, accentuated by the spatial and temporal variability of the rain in Colombia and in special the equatorial zone. Additional to this is the short-term storage capacity of the reservoir, which another challenge is the limited regulation capacity. Summed to the river capacity, which allows discharging until 600 m3/s without causing problems to the downstream infrastructure.
The work presented is a designed and implemented ed methodology to increase the economic profits of the asset, reducing the risks involved in the operation of the reservoir. The product of this study were seasonal operation rules to be used for the hydropower operators. The rules were tested by computational simulation before were implemented in the in the real operations.
The process followed to determine the proper operation rules could be summarized in 4 activities: first the stochastic characterization of the historical energy prices and the historical daily water inflows of the reservoir. Second, the estimation of the extreme flows that could enter in the future into the reservoir, this with the objective to create operation rules that could manage without any inconvenient the maximum probable inflows. Third, determine the gate operation rules that could manage the maximum probable design events. Finally, develop a probabilistic risk analysis of the information to determine the reservoir operation rule that balance the benefits vs the potential loses for keeping the water elevation high.
