Modelling the impacts of reservoir operations on the downstream riparian vegetation and fish habitats in the Lijiang River

摘要

River flow regulations have great impact on the downstream aquatic ecosystem. It is important toninvestigate the response of target species to the changes in hydrological regimes so that we cannexplore possible remediation measures. Ecohydraulics models that integrate hydrodynamicsnprocesses and ecological processes have been shown to be efficient in achieving these objectives.nThis study developed an integrated model which combined a two-dimensional hydrodynamicnmodule with a vegetation evolution module and a fish habitat module. Owing to the abilitynto represent spatial heterogeneity and local interactions, the vegetation module used annunstructured cellular automata (UCA) approach. To describe the ambiguous relations betweennthe physical conditions and habitat suitability, a fuzzy inference method was applied to the fishnhabitat module. The developed model was applied to a compound channel of the Lijiang Rivernin southwest China, which has been greatly affected by the flow regulations of the QingshitannReservoir for navigation purposes. Through scenario simulations, the effects of flow regulation onnriparian vegetation and fish habitat were analyzed. According to the results, water releases in thendry season imposed negative effects on the downstream semi-aquatic plant Rumex maritimusn(R. maritimus) and Polygonum hydropiper (P. hydropiper) and favored the upland speciesnLeonurus heterophyllus (L. heterophyllus). Regarding to the effects on fish Spinibarbusnhollandi (S. hollandi) the results showed that water releases increased the suitability of thenspawning conditions, especially during wet and dry years, but had little impact on thenoverwintering conditions.