Ecological hydrograph based on Schizothorax chongi habitat conservation in the dewatered river channel between Jinping cascaded dams

Hydropower development changes the river hydrological regime,thereby altering river ecosystem significantly.One important measure for reducing degradation of ecosystem is to determine ecological flow and implement it by reservoir operation.This paper described a method to calculate river ecological flow based on fish habitat conservation and applied it to Jinping River Bend of Yalong River.Schizothorax chongi was selected as target species,and the fish habitat model coupling with water environmental model was developed according to the relationship between fish and water environment factors.Moreover,improved hydraulic habitat suitability index(IHHS) and habitat fragment index(HFI) varying with discharge were discussed in this paper.Habitat area representing average annual flow was taken as a reference,and then ecological hydrographs under different habitat conservation levels were calculated considering season variation and life stages of fish.Compared to the natural condition,the model results indicated that the reservoir operation clearly influenced the habitat of the target fish.It was proposed to ensure flow releases to maintain 70%-90% habitat in section after joint while about 60% before joint.