| In recent decades,with the rapid development of China’s economy,urban waterlogging has become an important factor affecting human survival and high-quality social development.In the process of accelerating urbanization,the land on both sides of the river is constantly being occupied.At the same time,global climate change is abnormal,and short-duration rainstorms often occur.After a large number of urban land is hard-bottomed,the flood directly flows into the river,and the flood control and drainage pressure of the river increases sharply,resulting in frequent urban floods and waterlogging,which seriously threatens the urban flood control barrier.In addition,due to the uneven distribution of water resources in China,the demand for natural water and urban ecological water is not enough to match,resulting in urban rivers in some seasons cannot meet the normal ecological base flow,the contradiction between supply and demand of water resources is becoming more and more prominent.Therefore,improving the supply capacity of regional water resources and constructing high-standard urban drainage pumping stations are necessary conditions for ensuring the safety of urban flood control,maintaining the urban water ecosystem,realizing the urban "Flowing water flows smoothly" and ensuring the high-quality development of regional economy.In this paper,the ancient canal and related rivers in the main urban area of Yangzhou City are taken as the research object.According to the drainage and water demand characteristics of the river in the region,the removal of Hedong gate at the original site is carried out.It is of great significance to demonstrate the drainage scale of the new Hedong pumping station and study the drainage scheduling scheme.The ancient canal area in the main city of Yangzhou has a large population and a large amount of economic agglomeration.It is a region of politics,economy,culture and living center.In recent years,with the completion of the Runyang River Project and the Yiyang River Gate,the main urban area of Yangzhou has formed a flood control circle with the west embankment of the Beijing-Hangzhou Canal,the north embankment of the Yangtze River,the east embankment of the Wutagou-Runyang River,and the south embankment of the Yanshan River as the closed flood control circle.The eastern section of the ancient canal and the Yiyang River no longer directly discharges the Yihan Mountain flood,but is the only channel for the outflow of waterlogging water from the main urban area into the river.The pattern of the flood in the hilly area of Yihan and the waterlogging water frame drainage in the plain polder area of the urban area has basically formed,but under this pattern,the problems existing in the drainage project of the ancient canal in the main urban area are as follows:（1）Drainage:Guazhou Pumping Station is connected with the Yangtze River at the south end of the ancient canal,so as to ensure the flood control safety of ancient canal drainage in the main urban area.However,the current situation in the east of the ancient canal is that Yangzhou Gate is connected to the Huaihe River.When the flood water of the ancient canal meets the high water levels of the Yangtze River and the Huaihe River,the self-discharge road will still be blocked or even completely unable to self-discharge,resulting in the elevation of the water levels of the ancient canal and the Yiyang River,and the increase of the flood control pressure of the internal dike,which seriously threatens the safety of flood control and waterlogging removal in the surrounding areas.Therefore,the construction of the pumping station project of Hedong gate and the full demonstration of its drainage scale and the optimal selection of the drainage scheduling scheme of the pumping station are the necessary conditions for ensuring the flood control safety of the ancient canal drainage in the main urban area.（2）Diversion:the ecological flow of the ancient canal originates from Shaobo Lake,and the current situation can only meet the ecological base flow needs of the ancient canal through the Hedong gate at the eastern end of the ancient canal.However,when the water level of Shaobo Lake is lower than the ecological water level of the ancient canal and the ancient canal needs to maintain the normal ecological water level,the existing Hedong gate function cannot realize the ecological water use of the urban area,it is difficult to guarantee the sustainable development of economy and society,realize the important goal of promoting the improvement of regional water ecological environment and meet the new requirements of the construction of ecological civilization.Therefore,the new Hedong pumping station project should increase the pumping function on the basis of planning drainage,and fully demonstrate its water diversion scale.Based on the full analysis of the region’s natural geography,hydrology and meteorology,flood characteristics and the demand for drainage of the ancient canal in Yangzhou City,this paper fully demonstrates the drainage scale of the newly-built Hedong pumping station by combining the start-up combination mode of Guazhou Pumping Station with the requirements of urban living water flow,and selects its drainage scheduling scheme,and achieves the following results:（1）The necessity of removing Hedong gate and building Hedong pumping station and the reliability of drainage scale are fully demonstrated through the investigation of drainage status in the main urban area and a series of data analysis of local rainfall and water level encounters of Yangtze River and Huaihe River.（2）In view of the crisscross of the drainage channels of the ancient canal in Yangzhou City,the complex layout of the external drainage pumping stations and other hydraulic structures in the ancient canal,the MIKE 11 HD river network model（drainage）was established,and its characteristics of strong operability and high accuracy were used to lay the foundation for demonstrating the drainage scale of the new Hedong pumping station and selecting the optimal drainage scheduling scheme.（3）After analyzing the maximum and minimum control water levels of the important nodes of the ancient canal,the total scale of the external drainage stations is 242 m3/s,of which the drainage scale of Guazhou Pumping Station is 170 m3/s and that of Hedong pumping station is 72m3/s.Based on this,four different drainage scheduling schemes of Hedong pumping station combined with Guazhou Pumping Station are developed.Subsequently,the river network was generalized,the initial conditions and boundary conditions were determined,and the roughness parameters of the river network were calibrated.Through the established river network hydrodynamic model into the numerical simulation.The initial water level of the ancient canal is reasonably lowered before the rainstorm,and the river regulation and storage capacity of the ancient canal and tributaries is fully utilized.The water level of the important nodes under different drainage scheduling schemes is analyzed,and the reliability of the drainage scale of Hedong pumping station is fully demonstrated.By comparing the schemes,a more suitable drainage scheduling scheme is selected.（4）In view of the insufficient ecological base flow of the ancient canal,through the analysis of the diversion function of the original Hedong gate and the analysis of the diversion probability of the newly-built Hedong pumping station,the importance of increasing the diversion function of the Hedong pumping station on the basis of the planning pumping and drainage function is demonstrated.At the same time,based on the analysis of the current situation of the ancient canal diversion,through the calculation and analysis of the required ecological replenishment flow and the simulation review of the ecological replenishment flow velocity through the MIKE 11 HD river network model（diversion）,it is fully demonstrated that the diversion scale of the Hedong pumping station 29 m3/s can meet the needs of the ecological diversion of the ancient canal. |
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