Mitigating Environmental Impacts of Small Hydropower Plants Through Advanced Hydraulic Modelling

Abstract This study investigates the hydraulic conditions of the tailrace channel at the Perehonivka mini hydropower plant (HPP) in Ukraine using 2D computer modelling with HEC-RAS 6.6. Hydropower facilities, while essential for renewable energy generation and water regulation, can experience negative hydraulic effects that compromise equipment performance, structural integrity, and environmental stability. The Perehonivka HPP, initially constructed in the 1950s and reconstructed in 2014, was analyzed under two flow scenarios: regular turbine operation (4.6 m 3 /s) and combined turbine and spillway operation during a 5% probability flood event (397 m 3 /s). The simulation results revealed subcritical flow under normal operation, but excessive velocity values that may cause erosion in the inlet canal. During flood events, water overflowed the canals and exceeded the designed hydraulic capacity, highlighting risks of structural damage and flooding. These results emphasize the importance of modern hydraulic modelling in the design and reconstruction of HPPs to ensure operational efficiency and minimize environmental and structural risks. The study supports the need for updated infrastructure designs aligned with current flood probability standards.