Study On Ecological Water Demand In The Yang River Valley Based On Fish Habitat Model

The damage to water ecosystems of rivers and the loss of water resources have become more prominent,because of the rapid development of social economy,the accelerated expansion of cities and the intensification of human activities.There is a lack of procedural research on ecological flow research of rivers.The life history of aquatic organisms is closely related to hydrological processes.The fish life process is deeply relevant to the river hydrological rhythm,which plays an important guiding role in the formulation of river ecological flow targets.The ecological flow is determined by the indicative organisms,which is concluded that the ecological water demand can better guarantee the health of river ecosystems.The Yang River Valley is a large tributary of the upper reaches of the Yongding River systems,which is a region with strong human disturbance.As the main source of water in the Beijing area,the water resources endowment is poor,the demand for water in human society is increasing,and neglecting the health protection of river ecosystems,which results in serious ecological degradation.Research on ecological water demand in the Yang River Valley through indicative organisms and it also provides theoretical support for ecological restoration and sustainable use of water resources in the Beijing-Tianjin-Hebei region.Based on the field in situ monitoring data,this paper through the statistical analysis and cluster analysis were studied to illuminating the composition and spatial distribution law of the fish community in the Yang River Valley.By analyzing the dominant fish species in the Yang River Valley,combined with expert consultation methods,the indigenous target species suitable for determining the target value of the ecological flow are identified.Based on the habitat methods,a two-dimensional hydrodynamic model was constructed by the River 2D model,and the ecological water demand of the Yang River Valley was studied based on the model simulation results.Studies have shown:(1)Compared with historical monitoring data,fish communities in the Yang River Valley have been reduced by 4-6 species,and fish biodiversity has decreased significantly.From the spatial distribution,fish species in the Yang River Valley have formed two community types:Group I which mainly distributes in the upper mountainous area of rivers,Group II which mainly distributes in the plain cities area and the transition area from mountainous area to plain area.It is necessary to minimize the disturbance to the fish habitat and ecosystem during urbanization and human activities.(2)Through the comprehensive analysis,the indigenous target species Phoxinus lagowskii and the corresponding research river section of the ecological flow research in the Yang River Valley were determined.The River 2D model,which was constructed based on hydrological data and the river channel measured topographic data,and the suitability index of Phoxinus lagowskii were used to simulate the outlet flow rate under 5 different inlet flow conditions is in accordance with the range of 70%Qin?Qout?130%Qin,it was proved that the fitted effect was good,to obtain the Weighted Useable Area(WUA)of Phoxinus lagowskii.(3)Based on the stimulated corresponding flow rate of the maximum WUA,1.6 m~3/s was considered as the target value of the ecological flow of the Yang River Valley,and the ecological water requirement of the sensitive period of Phoxinus lagowskii spawning is estimated to be16.6 million m~3.which can guarantee the living environment of Phoxinus lagowskii to the maximum extent,better revive and protect the fish community structure and biodiversity,and provide important theoretical support for the restoration of aquatic organisms and the ecosystem health protection of the Yang River Valley.The Yang River Valley is a strong human disturbance zone,in which the aquatic organisms are seriously degraded,and the ecological flow is difficult to guarantee.And it is impossible to ensure that the flow of water remains at the target value in the actual hydrological process.Therefore,based on this model simulation of curve results of the Q-WUA of Phoxinus lagowskii in this paper,the 0.4 m~3/s-2.0 m~3/s is suggested as the suitable range of ecological flow process for biological protection in the Yang River Valley,the corresponding suitable ecological water demand protection range is 4.1 million m~3-20.7 million m~3,which as the key basis for the restoration of aquatic organisms,ecological restoration,river ecological flow and ecological water demand development in the Beijing-Tianjin-Hebei region.