Study On Initiated Water Level Of River Drainage In Polder Area Considering Irrigation And Drainage

In plain area,the polder area is a unique form of agricultural development in the long-term water control practice.The area where the reclamation area is located is generally rich in water resources,fertile land,and is mild in temperature,which suits crop growth,human production and life.With the development of urbanization in modern times,many large and medium-sized cities have emerged in the polder area.Therefore,the polder area has further become a place where industrial and agricultural development are advanced,resource elements converged,with relatively affluent wealth.On one hand,the terrain of the polder area is flat,the terrain is low-lying,and the water lies low during the flood period,so it is prone to flood disasters.On the other hand,the industrial and agricultural areas in the polder area are developed,so much water are required,and the local water resources cannot meet the water demand.Taking Beizhou Polder Area as an example,this paper studies the relationship between the local water resources utilization rate and the initial water level of the river drainage,and the relationship between the pumping station design drainage flow and the initial water level of the river drainage.Thus,a method of reasonably determining the initial water level of river drainage in polder area is put forward,which considers both the utilization of local water resources and the drainage of waterlogging.The study result can provide reference for the methodology and management of the river channel of the same type.(1)Study on the relationship between local water resources utilization rate and initial water level of river drainageThe industrial water and domestic water for Beizhou Polder Area are mainly taken from the Yangtze River outside the region.The local water resources are mainly used for agricultural irrigation.The characteristics are that when the local water resources are not enough,the water resources of agricultural irrigation are supplemented by water from other places,and different underlying surfaces are considered.Conditional rainfall runoff and irrigation water demand model,local water resources and irrigation water demand calculated from local daily rainfall and evaporation data.According to the calculated local water resources and irrigation water demand,the ecological water level and the initial water level of drainage in the polder area were taken as the control,and the water storage in the river was calculated and analyzed by the principle of water balance.Then the amount of water resources used and the utilization rate of water resources were counted.Studies have shown that the local water resource utilization rate has a close relationship with rainfall,local water resources,and initial water level of drainage.The average annual water resource utilization rate has a linear relationship with the initial water level of the drainage,which is positively correlated.Affected by the amount of rainfall and local water resources,the relationship between the local water resources utilization rate and the initial water level in different years is different.When the initial water level of the drainage is between 2.4m and 3m,the highest water resource utilization value is 1,and the lowest value.is 0.04.(2)Study on the relationship between designed drainage flow and initial water level of river drainageFor the drowning in the polder area,the pumping station needs to be discharged through the pumping station,and the river channel in the polder area can adjust the characteristics of some drowning water in a short period of time.The storms with different frequencies were designed to calculate the flow rate of the river channel entering the polder area.The water level and the design drain water level were considered to calculate the designed drainage flow.After calculation,under different water surface rates,the relationship between the initial water level and the drainage modulus of different drainages of Beizhou Polder Area,the storage volume of different units and the modulus of drainage were calculated.Studies have shown that there is an exponential function between the drainage modulus and the initial water level of the drainage,and the two parameters in the exponential function have a fixed function relationship with the water surface rate.The relationship between the storage volume per unit area and the modulus of drainage is still known to satisfy the exponential function,and the two parameters in the exponential function also have a fixed functional relationship with the water surface rate.(3)Study on determining the starting water level of suitable river drainageUnder the premise of determining the ecological water level of the river channel and designing the drainage water level,the initial water level of the river drainage is high,which is beneficial to make full use of local water resources,but it is not conducive to drainage and vice versa.Taking Beizhou Polder Area as an example,this paper studies how to control the initial drainage water level of rivers in the polder area in a reasonable range or optimal location.According to the quantitative study of local water resources utilization and flood storage,the benefits of local water resources utilization in the polder area were calculated,and the losses caused by flood risk were calculated as well.The results has been analyzed and compared,and the appropriate initial drainage water level of Beizhou Polder Area have been preliminarily obtained.The range is between 2.55m and 2.85m.In order to obtain a more suitable starting water level for drainage,a collaborative decision-making model has been further constructed to solve the optimal water level.According to the water resource utilization benefit and the flood loss combined model,the water level is suitable between 2.65m and 2.8m and the optimal water level is 2.8m.Through the relevant conclusions obtained from the study on the relationship between the initial water level and the water resource utilization rate,the drainage modulus and the storage volume in the reclamation area,new ideas for the treatment of the reclamation area can be provided,and at the same time,the water resources and river channels in the reclamation area will be saved.The ability is fully utilized to reduce the flood damage during the flood season and ensure the rational use of daily water resources,laying a good foundation for the development of the reclamation area.