Evaluation of habitat quality and ecological flow in a regulated waterway

Abstract

Abstract Dam control changes the hydraulic environment and hydrological rhythm of rivers; to explore the causes of fish habitat loss and influence of river regulation in such rivers, the downstream curving reaches of Shaying River were cut off. Grass, silver, and bighead carp were selected as the research targets, and the impact of waterway regulation and the effect of gravel mounds on the target fish habitat were studied using numerical simulation. The results show that the original channel's hydraulic environment is similar to the artificial channel, and the target fish spawning habitat is limited, which is an important reason for the shortage of fish resources in the research area. The reconstructed channel can meet the river's navigation demands and improve the channel's flood discharge capacity. The habitat method was used to estimate the minimum and appropriate ecological flows of the target fish at each growth stage in the original and reconstructed rivers. Under the appropriate ecological flow, the weighted usable area (WUA) of juvenile, migratory, and spawning habitats of the target fish in the reconstructed river increased by 168, 24, and 580%, respectively, compared to the original channel, while the WUA of adult fish that preferred a slow-water environment decreased by 62%, effectively improving the target fish's spawning environment.