Application of a fish habitat model to assess habitat fragmentation using high flow and sediment transport in the Rumei Dam in Lancang River (China)

Abstract

Dam construction and operation can result in serious disturbances to the downstream flow regime and fluvial process, river morphology and the river's ecological condition worldwide. To understand the effects of discharge and sedimentation on fish habitats and ecosystems, an ecohydraulic approach was applied to one of the mega hydropower schemes in the downstream Lancang River (Tibet). The approach comprised a dam operation module with high flow and sediment transport and the application of a dynamic fish habitat model for assessing habitat fragmentation of two targeted fish species: Schizothorax prenanti (S. prenanti) and Schizothorax davidi (S. davidi). The hydrodynamics of the river system and the assessed fish habitat show a significant impact of dam construction and operation on the downstream riverine ecosystem, in which fish habitats were found rapidly deteriorated with the destruction of feeding and reproductive grounds. To improve fish habitat after dam construction, the sediment supplement was applied to the river and shown to be a useful restoration strategy, which recovers the habitat fragmentation of target fish. Our model not only is useful to predict dam operation impacts on the Lancang River's ecological status but also shows great potential in mitigating hydropower‐induced environmental impacts and developing river conservation guidelines worldwide.

Assessment of Fish Habitats and Suitable Ecological Flow under Hydropower Operation

“…However, despite the social and economic benefits, water conservancy projects like reservoirs inevitably disrupt river connectivity, modifying hydrological conditions, including water level, flow, temperature, turbidity, and more [3][4][5]. These changes result in a decrease in the habitat suitability for fish, notably impacting the existing fish community structure and distribution within the watershed [6,7]. Preserving appropriate ecological flow and habitat conditions is a prerequisite for ensuring the reproduction of fish [8,9].…”

Integrating ecohydrology and ecohydraulics

“…However, the implementation of e-flows in regulated rivers has become increasingly powerful means to protect biodiversity and ecosystem services and to address multiple social, political and economic challenges of river basin management around the world. For instance, with e-flow guidance, the HHM has become very useful for evaluating the fragmented habitat of the two targeted fish species Schizothorax prenanti (S. prenanti) and Schizothorax davidi (S. davidi) in the downstream Lancang River (Tibet) under the dam operation module under high flow and sediment transport conditions (Yang et al, 2023). Wu et al (2024), on the other hand, assessed fringing vegetation conditions of the Hattah Lakes floodplain in south-east Australia by modelling the 32-year Landsat imagery data of the normalized difference vegetation index (NDVI) and environmental water allocations and natural floods and identified that the environmental water delivered 3 months prior to the Landsat image date is a crucial factor for better vegetation condition.…”

“…However, in regulated river systems, the construction of barriers has greatly fragmented the habitats causing a significant biodiversity decline. Regulation has severely impeded movement of aquatic organisms, geomorphology and altered natural flow regimes (Sofi et al, 2023;Yang et al, 2023). However, the implementation of e-flows in regulated rivers has become increasingly powerful means to protect biodiversity and ecosystem services and to address multiple social, political and economic challenges of river basin management around the world.…”