Hydrodynamic modeling of the Uruguay River in the Turvo State Park stretchs

Abstract

The flow pulses generated by the operation of a Hydroelectric Power Plant (HPP) modify the water regime downstream. The stretch of the Uruguay River covered in this study begins after the Foz do Chapecó HPP and ends at the Alto Uruguai fluviometric station, downstream of the Turvo State Park (TSP), located in Derrubadas/RS. The PET is home to the Yucumã Falls, the largest longitudinal waterfall in the world, with extraordinary scenic beauty, great relevance for tourism, and being very susceptible to flow pulses from the upstream HPP. The stretch has the Itapiranga HPP project under study, located much closer to the TSP. A one-dimensional hydrodynamic model was structured in HEC RAS to simulate the flow pulses of the plants in the stretch. The model was calibrated for a dry period using data from available fluviometric stations. Simulation 1 was related to the flow pulses of the Foz do Chapecó HPP, and Simulation 2 was related to a hypothetical flow regime if a HPP were built in Itapiranga. Simulation 1 (calibration) showed consistency compared to the observed data, with coefficients of determination (R²) between 0.8562 and 0.9837, Nash-Sutcliffe coefficients (NS) varying from 0.8515 to 0.9832, and the logarithmic coefficient Nash-Sutcliffe (NSlog) in the range of 0.8557 to 0.9716. Simulation 2 showed that, considering the adopted scenario of a new HPP in Itapiranga, changes in the water regime of the Uruguay River in the Yucumã Falls would include an increase of up to 15.1% in maximum flows, a reduction of up to 27. 2% in minimum flows, and an increase of up to 122.2% in the amplitude of the studied flows.