| Shipping is one of the most important functions of rivers to influence the development of human society.In recent years,China’s inland navigation has been developing rapidly,and the construction,management and maintenance of waterways have been in the world’s leading level.At present,the basic functions such as safety of ship passage and navigability of waterways are no longer the only goal of shipping development,and the synergy between shipping development and ecological protection is valued as an effective means to give full play to the ecological effects of rivers.In this thesis,the main distribution habitat type of the four fish in the Three Gorges Variable Return Zone of the upper Yangtze River-continuous shallow and deep pools-is investigated through high-precision probabilistic flume tests,and the hydrodynamic characteristics and the response law of typical four fish are studied and applied to the four fish in the Three Gorges Variable Return Zone Zhongdui River channel management project.The paper also applied it to the study of habitat creation in the Zhongdui River section of the Three Gorges Variable Return Zone,and obtained the recommended plan and effect of habitat creation in the Zhongdui River section by combining field research and mathematical model calculation analysis.The main research contents and conclusions of the paper are as follows:(1)Three consecutive dams were arranged on one side of the high-precision experimental flume to form a continuous shallow-deep pool and carry out hydrodynamic experimental research.The PIV system,a laser particle imaging velocity measurement instrument,was used to measure the vertical flow field distribution at different deep pool locations at different water depths and analyze the distribution characteristics of flow velocity,turbulent energy and Reynolds stress.The results show that the flow velocity of the main channel on the outer side of the shallow ridge is much larger than that of the two deep pools,and the average flow velocity of the upstream deep pool is smaller than that of the downstream deep pool,and the distribution of flow velocity of the two deep pools is inconsistent;after the inundation of the dam,the greater the water depth on the dam,the larger the proportion of the area occupied by the transition zone of the upstream deep pool and the proportion of the area occupied by the downstream deep pool downstream;the change patterns of turbulent kinetic energy and Reynolds stress in the deep pools are more similar,and the trend of the vertical line change When the dam is not flooded,the average turbulent energy and Reynolds stress in the upstream deep pool are smaller than those in the downstream deep pool,and after the dam is flooded,the average turbulent energy and Reynolds stress in the upstream deep pool are larger than those in the downstream deep pool.(2)Based on the hydrodynamic characteristics of the continuous shallow-deep pool,the fish behavioral characteristics were tested.5.0 cm grass carp fry were selected based on the equation of critical swimming speed versus body length and pre-experiments,and the behavioral response of grass carp was tracked and monitored by high-definition camera equipment arranged on the top and side.The analysis results showed that the higher the flow velocity,the higher the fish suitability,the higher the turbulent kinetic energy and Reynolds stress,and the fish suitability first increased and then decreased within the suitable range of current conditions.The fish swimming path mostly chose the relatively high flow velocity,medium turbulent kinetic energy and low Reynolds stress in the deep pool,and the relative location preference of fish was most preferred in the upstream nearshore area of the upstream deep pool,followed by the upstream and downstream nearshore areas of the downstream deep pool,where most of the areas with high fish suitability were distributed.(3)According to the results of fish distribution research in the Zhongdui River section,the habitat creation plan can be created by arranging three continuous dams at the three rock beam protrusions in the anticline moraine to create a continuous shoal-deep pool habitat;using the three-dimensional water flow mathematical model MIKE 3 to calculate the characteristics of the deep pool water distribution before and after the plan,combined with the conclusions of the flume test study,the results show that the flow speed and flow suitability after the plan are significantly improved,the turbulence energy suitability is reduced,the comprehensive water flow conditions are more suitable for fish survival,and the channel navigable water flow conditions also meet the requirements of channel regulation. |
