Author(s): Jakob Siedersleben; Stefan Jocham; Stefan Achleitner; Markus Aufleger

Linked Author(s): Stefan Jocham, Stefan Achleitner, Markus Aufleger

Keywords: Hydropower; Sediment transport; Residual flow; Environmental flow; Numerical modelling

Abstract: The hydropower facility in Reutte, Austria is undergoing modernization, and the capacity of the diversion hydropower plant is set to be increased. The facility is located at the Lech, an alpine river transporting high rates of coarse bed load. A bedload entrapment was constructed in 2017 upstream of the facility. Combined with the highly dynamic annual flows of the Lech, it leads to a high degree of uncertainty in the input parameters. In the investigated section, the Lech has a mean annual discharge of 44 m3/s, and the mean incoming bedload volume is about 110000 m3/y. Excavations from the residual flow reach are necessary to maintain stable riverbed levels. A 2D numerical morphodynamic model was set up to investigate the morphological impact of increasing the diversion discharge from 24 m3/s to 28 m3/s or 36 m3/s on the residual flow reach. The results show that an increase in diversion discharge leads to an increase in aggradation tendencies in the residual flow reach. However, the expected aggradation magnitude differs for different scenarios. The expected deposition of an increase to 28 m3/s is strongly dependent on the hydrograph, an increase to 36 m3/s leads to an increase of deposited volume of about 42 %. Overall, the highly dynamic nature of the Lech and a strong dependence on the hydrograph result in high ranges of possible deposited volumes, which emphasizes the uncertainty of the input database.

DOI: https://doi.org/10.3850/978-90-833476-1-5_iahr40wc-p0713-cd

Year: 2023