Environmental flow assessments based on habitat suitable model considering ecological adaptation in estuaries

摘要

In an estuary, distributions in environmental factors, habitat losses, and biological processes are threatened directly by upstream freshwater withdrawal or by alteration of the natural flow regime resulting from the construction and regulation of hydraulic projects worldwide. In order to define the quantity, quality, and timing of the freshwater inflows required to sustain estuarine ecosystems health, environmental flow assessments has been taken as a critical issue to achieve the goals of water use balance between human activities and ecosystems in estuaries. In this study, we developed a habitat suitable model to understand the ecological response to hydrological alterations in an estuary. Based on the simulation of critical environmental factors distribution under action of river flows and tidal currents in estuaries, potential suitable habitats for typical species could be identified by mapping different levels of Habitat Suitability Index (HSI) in the estuary, which makes ecological adaptation be involved in the environmental flow assessments. Habitat Suitability Index (HSI) for typical species was determined by fuzzy logic method, and the Habitat Aggregation Index (HAI) was built considering the internal patches and fragmentation of the habitat. Based on trade-off analysis of HSI and HFI requirements for typical specie and requirements of river flows for different species, environmental flows could be recommended under different scenarios of river discharges. The proposed method was applied in the Yellow River Estuary, China. The results indicated that, non-linear relationship existed between potential suitable habitats and freshwater inflows. The proposed approach is flexible in environmental flow assessments with potential changes of estuaries in the future.