Study On Landform Evolution And Hydrodynamic Characteristics Of Chinese Sturgeon’s Spawning Grounds

Chinese sturgeon, living in the coastal waters most of their life and only migrating upstream to spawn when they reach their sexual maturity, is a large wading river migratory fish. Before the construction of Gezhouba Dam, the sturgeon spawning grounds distributed from Xinshi to Peiling with a total of 16 places. By Gezhouba Dam water conservancy hub halt the flow of the water, Chinese sturgeon’s migratory routes were cut off below the Gezhouba Dam. Then a new spawning ground under the dam has been found in Yichang, which is currently the only known Chinese sturgeon’s spawning ground of Yangtze river.In this article, the evolution process of Chinese sturgeon spawning terrain under Gezhouba dam’s downstream has been analyzed through prototype research, physical model and mathematical model. The water flow velocity distribution and flow conditions of the Chinese sturgeon spawning grounds was researched under working condition which is derived from the actual running situation. Finally, preliminary improvement measures are put forward based on the adaptability of Chinese sturgeon. The main conclusions of this study can be summed up as follows:(1)Summarizing the biological characteristics and Chinese sturgeon spawning grounds distribution and hydrodynamic conditions through the previous research and the field investigation.(2)There are two periods during the 45 years, in which the riverbed terrain structure under Gezhouba Dam changed significantly due to human activities, started form 1970 to 2015. The first session is the construction period of Gezhouba Dam(1970-1988), and the second session is the period about modified project of river regime under Gezhouba Dam(2004-2006). At other times, the change of riverbed mainly due to natural erosion and deposition.(3)The spawning grounds’ topographic feature under Gezhouba Dam are similar with the spawning grounds of history. There is a certain area under the Gezhouba Dam,which can be suitable for Chinese sturgeon spawning with hydrodynamic conditions meet they needs, such as water depth, flow velocity and vorticity. As the change of the terrain in several years, the suitability for Chinese sturgeon propagation has beendecreased.(4)Two measures which may improve the conditions of spawning and breeding for Chinese sturgeon have been put forward. One is to improve the structure of the terrain and the other is to strengthen discharge when Chinese sturgeon will breed.