Impact of reservoir operating rules on the performance of multi-purpose cascade hydroelectric systems: The case of Tietê-Paraná Waterway

This paper addresses the impact of reservoir operating rules on the performance of multi-purpose cascade hydroelectric systems through the case study of the Tietê-Paraná Waterway (TWP). The TWP reservoirs operate with the purposes of power generation, navigation, and flood control. Located at the downstream part of the Paraná river basin in southeast Brazil the TWP had to be closed from May 2014 to December 2015 due to the system operator's strategy of preserving water on the upstream reservoirs incurring on the empting of the main TWP reservoir during a drought period. Since reservoir operating rules that preserve storage on downstream reservoirs are more efficient from the cascade generation point of view, this paper investigates the impact of using reservoir operating rules that preserve the storage in the TWP reservoirs on the operation performance of the Paraná river basin system during the drought period. A two-step simulation procedure was applied: First, based on post operation data from May 2011 to December 2015, the operation of the Paraná river basin was reproduced by simulation on monthly basis. Then, an alternative operation that produces the same hydropower generation was obtained by simulation using reservoir operating rules that preserve storage on the reservoirs of the TWP. The results show that if operating rules that give priority to storage in the TWP reservoirs were used in the Paraná river basin during the drought period it would be possible to produce the same hydropower generation while respecting the flood control constraints and avoiding closing the TWP.