| The Chaotianmen-Fuling reach in the fluctuating backwater area of the Three Gorges Reservoir is the national aquatic species resource reserve of Four Domestic Fishes in the upper reaches of the Changjiang River.National strategies such as the Changjiang River Economic Belt and the construction of traffic power require the construction of 4.5m waterway from Chaotianmen to Fuling reach as soon as possible.Around the regulation principle of “ecological priority”,the 4.5m waterway construction project from Chaotianmen to Fuling will take into account the construction of the fish habitat area in this section,so as to realize the coordination of shipping development and ecological protection,and establish the ecological waterway model of the upper Changjiang River.In this paper,aiming at the problem of fish habitat construction in the 4.5m channel project from Chaotianmen to Fuling,the Zhongdui River was selected to carry out the field monitoring of fish resource distribution.The distribution of fish resources in the Zhongdui River was analyzed,and the hydraulic parameters such as velocity of fish habitat demand were determined.On this basis,the fish habitat construction scheme of the nearshore continuous deep pool was proposed.The two-dimensional flow mathematical model was used to simulate the change of hydrodynamic conditions under the parameters,and the key parameters such as dam height and dam length of the continuous shallow-deep pool habitat construction scheme of the river section were obtained.The results show that:(1)Based on the results of previous monitoring,the suitable flow rate of the fish habitat should be less than 1.5m/s.Combined with the analysis of topographic characteristics and sediment scouring and silting characteristics,it is determined that the shoal-deep pool type can be used as a scheme model for fish habitat construction in Zhongdui reach.(2)Taking the 0.8m/s interval as the flow index of fish suitable habitat,through setting different parameters for the dam height and length,the influence of the dam height and length on the habitat area is preliminarily obtained: when the flow is larger,the area of suitable area is less;when the dam length is constant,with the increase of the dam height,the area of suitable area mainly increases,and the growth rate is gentle when the dam height is 152.0m;when the dam height is constant,the area of suitable area mainly increases with the increase of dam length,and the change is obvious.(3)Considering the effects of dam length and dam height on fish habitat and navigation safety,the scheme with dam height of 152.0 m and dam lengths of 170 m,180 m and 155 m from 1# dam to 3# dam is selected as the scheme of continuous shoaldeep pool fish habitat.After the scheme,the suitable flow velocity range of fish increases,which may lead to sediment deposition in a small part of the beach.However,the flow with slow flow velocity behind the dam can enrich phytoplankton here,and provide a good breeding environment for other aquatic organisms.In addition,the scheme not only does not destroy the original spawning ground,but also increases the range of the tranquil flow and back flow of the beach,which provides a broader spawning ground area for the spawning of viscid eggs.After the habitat construction scheme,ecological artificial reefs can be used as auxiliary measures to guide the fish to move to the suitable area,which can provide more favorable living places for fishes. |
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