| The construction of the Gezhouba Project blockes the migration path of Chinese sturgeon,leading to the loss of a large area of habitat and key spawning ground,Chinese sturgeon is forced to form a new spawning ground under the Gezhouba Dam.Since the impoundment of the Three Gorges reservoir,the water environment of the spawning ground of Chinese sturgeon under the Gezhouba Dam has been changed,resulting in the decrease of the number of parent sturgeons,the decrease of spawning frequency,and the continuous decline of the scale and quality of natural reproduction.In view of the adverse effects of the Three Gorges and Gezhouba water conservancy projects on the natural reproduction and spawning water environment of the Chinese sturgeon,it is urgent to carry out research on the evolution and artificial optimization of the water environment of the spawning ground in order to protect the sustainable development of the resources of the Chinese sturgeon.Based on the evaluation model of spawning fitness of Chinese sturgeons spawning ground,this paper analyzes and evaluates the spawning fitness of water environment of spawning ground under the Gezhouba dam over the years,obtains the evolution process of spawning position,riverbed topography,riverbed sediment,water quality and hydrodynamic environment of Chinese sturgeon after the impoundment and operation of the Three Gorges Project,identifies the key factors of water environment change of Chinese sturgeon spawning ground under Gezhouba Dam.The scheme of artificial optimization of water environment of spawning ground is put forward,and the effect of the optimization scheme is evaluated.The main research contents and conclusions are as follows:(1)Through data collection and field investigation,the water environment requirements of natural reproduction of Chinese sturgeon are clarified,and the habitat suitability assessment methods are analyzed.According to the water environment characteristics of spawning grounds of Chinese sturgeon under Gezhouba dam,the evaluation model of spawning suitability of spawning grounds of Chinese sturgeon is constructed based on IFIM method.At the same time,the hydrodynamic model of spawning river section of Chinese sturgeons under Gezhouba is built,and the model is determined by field measurement data.(2)Based on the established spawning fitness model of Chinese sturgeon spawning ground under the Gezhouba Dam,the suitability of water environment of Chinese sturgeon spawning ground under the Gezhouba Dam for natural reproduction of Chinese sturgeon is evaluated,The evolution process of water environment of Chinese sturgeons spawning ground under the Gezhouba Dam after the impoundment of the Three Gorges project is obtained.The main evolution factors are identified as the underwater topography,sediment,hydrodynamic distribution characteristics and water temperature change of spawning ground.(3)According to the identified main change factors of water environment of Chinese sturgeon spawning ground under Gezhouba Dam,the artificial optimization scheme is proposed,and the evaluation model of spawning fitness of Chinese sturgeon spawning ground is used for comparative analysis and optimization evaluation.Taking the actual spawning day of Chinese sturgeon in 2010 as a typical working condition,the results show that four diversion dikes with length of 130m,width of 30m,interval of 40m and elevation of 33m are arranged along the water flow direction can optimize water depth and flow velocity,the weighted usable area of spawning ground is increased by 0.56km~2,the average water depth of actual spawning area is increased by 0.45m,and the average velocity is increased by 0.05m/s. |
