Ecological Geomorphology Simulation And Fish Substitution Habitat Evaluation In The Heishui River

While hydraulic engineering have made important contributions to the progress of human society,they have also brought many negative impacts on the ecological environment.Under the background of the hydropower development in Southwest China,and in response to the current ecological environment problems in the context of hydropower development in Southwest China,we have actively carried out studies on the protection of fish habitats,especially to actively explore The tributary habitat alternative technology that effectively mitigates the impact and damage caused by mainstream hydropower development on local sensitive and fragile ecosystems is of great significance for the conservation of fish resources under the development of southwest hydropower and to maintain the ecological security of the Yangtze River Economic Belt.This study selected the Heishui River,a first-level tributary of the left bank of the Baihetan Reservoir area of the Jinsha River,as a research object,and conducted an alternative research on tributary fish habitats.When the Baihetan Hydropower Station is normally filled with water,the combined effects of hydropower development on main stream and tributaries will greatly reduce the rapid fish habitat in the river basin,which will inevitably lead to significant impact on fish resources and water ecological environment.This study simulates the dam remove of the Heishui River fourth-grade power station,the Laomuhe Dam,and considers changes in hydrology,hydrodynamics,sediment transport,bed sediments,and other factors,in combination with the target fish and its objectives.Based on the habitat suitability curve,the model prediction method was used to analyze the effects of changes in river water and sediment transport patterns after the dam removal and the effects of changes in river geomorphology on fish habitats,and then to explore the Tributary habitat protection technologies based on the dam removal of the Heishuihe.The main conclusions obtained are as follows:1)The investigation of water ecology in Heishui River in November 2017 showed that 11 species of fishes were identified,belonging to 2 orders,4 families and 10 genera.The comprehensive representativeness and barrier effects of dams were selected Zacco platypus as the target fish for this study.The fish habitat survey results show that the the main hydrodynamic conditions of the main channel are shallow and acute in the Heishui River.The spatial heterogeneity of the riverbed landform is relatively high that creating complex and diverse hydrodynamic conditions which can provide a rich type of habitat unit for fish and other aquatic organisms.2)A 2D sediment transport model for the Heishuihe River was constructed.The simulation results showed that the sedimentation in the reservoir area before the demolition was mainly distributed as a “delta pattern”.After the removal of the dam,the sediments in the reservoir area are mainly characterized by top-down hydraulic erosion and bottom-up traceable erosion.The sediments discharged are deposited on river bank,deep pool,etc.where the flow rate slows down.In the long term after the removal of the dam,the morphological changes of the riverway in the reservoir area showed the trend of “first undercut and later broadening”.The features of sediment erosion and deposition in different periods are characterized by “flooding and erosion”,and after a complete hydrological cycle,the relative balance of erosion and siltation is achieved.3)Based on the river habitat restoration technology for the dams remove,it is expected that the natural flowing water habitat of fishes can be restored by about 30 km,and the quality of fish habitats in spawning periods can be effectively improved.Although the demolition of dams has caused a certain degree of impact on the downstream local fish habitat in the short term,but in the long run,the ecological restoration benefits are enormous.