Research On The Influence Of River-lake Connecting Project On Lake Pollutant Concentration Field

China’s water resources are characterized by "more water","less water","dirty water" and "muddy water",among which the water quality problem has always been a serious problem faced by China,which has greatly affected the people’s normal life and national economic development.China’s water pollution has the characteristics of complex,watershed and longterm,which leads to a long-term war to solve the problem of water pollution in China.Lakes are an important part of fresh water resources.There have been many large-scale lake pollution incidents in China,which have produced quite serious consequences.Gehu Lake is the second largest freshwater lake in southern Jiangsu Province,and its water quality is not optimistic.River lake connection project is a common method to improve the lake water renewal ability.River lake connection project is an excellent scheme to improve the water quality of Gehu Lake.In this paper,two examples are used to verify the accuracy of hydroinfo water information system’s hydrodynamic module and convection diffusion module.Based on the Gehu river lake connection project,the hydroinfo water information system is used to establish a hydrodynamic convection diffusion numerical model to simulate the change of Gehu Lake’s pollutant concentration field,and the overall water exchange energy of Gehu Lake is evaluated according to the water renewal time The water exchange capacity of five special water areas was evaluated,and the water areas with poor water exchange capacity were added with additional optimization conditions.The main results are as follows(1)The accuracy of the hydroinfo water conservancy information system in the calculation of two-dimensional scale hydrodynamic and pollutant convection and diffusion problems is satisfactory(2)The water renewal time of Gehu Lake under the river lake connection project is 31.5days,and the river lake connection project has significantly improved the water exchange capacity of Gehu Lake.Among the five special water areas,two water areas have strong water renewal ability,and the water renewal time is 5.25 days and 17.25 days respectively,so there is no need for additional engineering to optimize;two water areas have strong water renewal ability,and the water renewal time is 51.96 days and 51.13 days respectively,which can maintain the status quo;one water area has poor water renewal ability,and the water renewal time is 91.91 days,which needs additional engineering to optimize.(3)In view of the water area with poor water exchange capacity,this paper puts forward three schemes: inflow increasing scheme;Wuyi canal underdrain scheme;Taige canal widening scheme,and specifically formulates seven different working conditions.The simulation results show that increasing the flow rate can shorten the water exchange time obviously,but the actual situation is difficult to meet.There is a significant difference in the degree of shortening the renewal time of water body in the water area by building open channels with different widths,and the construction of 15 m open channel is the best scheme with high cost performance and high improvement effect.The widening of the Taige canal has a certain effect on shortening the renewal time of the water body,but the change of widening 10 m and 15 m is not obvious,and the improvement range is limited.Therefore,the construction of 15 m open channel is the best project optimization scheme.