Research On The Spatial Variability Of Eco-hydraulic Characteristics Of Four Famous Chinese Carps’ Important Spawning Grounds In The Middle Reach Of The Yangtze River

The four famous Chinese carps’ spawning grounds were located in the city in general river bend or rock spur into the middle of river in the middle reach of the Yangtze River, where owned the complex flow form and there were formed either large or small "ponding and vortex flow". After the damming of the Three Gorges Project, the river bed of the middle reaches were eroded by discharged unsaturated water, which had made the water depth deepen, flow velocity reduce, gradient slow, and had a great impact on the hydraulic characteristics of spawning grounds. It’s leaded to the change of spawning grounds’ location and water extent. According to research, the four famous Chinese carps’ spawning time or egg laying amount degradation were devoted to the released flow reduce, flood peak disappear and water temperature too low. The magnitude of stock of four famous Chinese carps are directly determined by the scale reduced of spawning grounds and decline of the output fish fry. Resurgence of magnitude of stock and germ plasma resources conservation are a very important and urgent task.It’s need to start with the disturbed habitats for recover the four famous Chinese carps’ germ plasma resources. This research based on eco-hydraulics studies for the four famous Chinese carps’ requirement of eco-hydraulic environment. Quantitative description of study areas based on some aspects:River morphology and the profile terrain, water velocity, water flow and cross-section mean vorticity strength.The conclusions of the research as follows:1. The water flow of four famous Chinese carps’ spawning grounds were stayed at a higher level. Meanwhile, the change of water velocity is necessary but not sufficient for access for four famous Chinese carps’ spawning.2. The mean value and range of water velocity in Baishazhou region was higher than the Yidu region and Nanxingzhou region. But the water velocity on the numerical range is also necessary but not sufficient for access.3. The favorable water velocity is distributed mainly in the junction of main flow and both sides of the water flow On a horizontal surface. What’s more, the junction area were the major suitable water area. At the same time, the favorable water velocity is distributed mainly below the cross section perpendicular bisector on the cross of water flow.4. The spatial distribution features of the CMVS value had showed the difference of spawning ground and non-spawning ground to some extent. The cross-section mean vorticity strength value mainly range from0.237-0.2652s-1. The CMVS value and the flow velocity of water were positively correlated, it needs further analysis for it might not as a linear relationship. The spatial variability characteristics of the CMVS value could be the hydrodynamics indication of four famous Chinese carps’spawning grounds in the middle reach of Yangtze River.