Study On Water Quality And Quantity Regulation From Shenwo Reservoir To Tangmazhai In Taizi River Basin

Taizi River is one of the important water systems in Liaoning Province.The Taizi River Basin has developed industry and agriculture and a high level of urbanization.However,with the continuous development of economy and society,the problem of water resources in the basin has become increasingly prominent,mainly manifested in the reduction of runoff and the continuous deterioration of water quality from upstream to downstream.A large number of practical studies show that through the joint regulation of water quality and quantity,the dual goals of efficient utilization of water resources and improvement of water ecological environment can be achieved.Aiming at the actual problems of water resources and water environment in Taizi River area,this paper analyzes the change trend and influencing factors of water quantity and quality in the basin,explores the response relationship between the change of pollutant concentration and the annual flow,and carries out the research on the joint operation scheme of water quality and water quantity of Guanyinge and Shenwo reservoir group with the goal of improving the water quality of the section from Shenwo reservoir to Tangmazhai.The main research contents and results are as follows:（1）Analysis on the change of water quantity and quality and its influencing factors in Taizi River Basin.Firstly,univariate linear regression method and Mann Kendall trend analysis method are used to identify the temporal and spatial variation law of inner diameter flow and water quality;The influencing factors of water quality and quantity change in the basin are analyzed from two aspects of rainfall change trend and land use,and the key river sections that need to improve water quality are determined.Secondly,based on the annual water quality changes in typical wet,normal and dry years,Spearman method is used to analyze the correlation between the concentration changes of NH₃-N,COD and TP and the annual flow,and explore the response relationship between water quality and flow.Finally,the hydrological segmentation method is used to quantify the point source emission and non-point source output of pollutants,and identify the sources and contribution rates of main pollutants.The results show that the inner diameter flow of Taizi River Basin shows a significant downward trend,the water pollution of the downstream river is serious,the non-point source pollution of the main stream is higher than that of the point source pollution,and the non-point source pollution of the tributary is slightly lower than that of the point source pollution.（2）Construction of two-dimensional hydrodynamic water quality model for the section from Shenwo reservoir to Tangmazhai.Firstly,by comparing and analyzing the advantages and disadvantages of different numerical models,Mike21 is selected to build the hydrodynamic water quality model.Secondly,the irregular triangular grid is divided,the upper and lower boundary conditions of the model are determined,and the hydrodynamic water quality coupling model of the section from the dam of Shenwo reservoir to Tangmazhai is established.Finally,the manning coefficient,diffusion coefficient,attenuation coefficient and other main parameters of the model are calibrated and verified by using the measured flow and water quality data from 2015 to 2017.The results show that the main parameters calibrated by the hydrodynamic water quality model are reasonable and feasible,and the relative error value and Nash coefficient of the simulation results meet the accuracy requirements of the model,which can be used to study the joint regulation scheme of water quality and quantity.（3）Study on water quality and quantity regulation scheme of the reach from Shenwo reservoir to Tangmazhai.Firstly,the water supply and consumption of Guanyinge reservoir and Shenwo reservoir are analyzed,and the schematic diagram of water supply system from Guanyinge reservoir to Tangmazhai is established.Secondly,in order to improve the water quality of Tangmazhai section of the downstream river channel and take the water supply guarantee rate as the constraint,the joint optimal operation model of Guanyinge and Shenwo reservoir group is established,coupled with the two-dimensional hydrodynamic water quality model of the section from the dam of Shenwo reservoir to Tangmazhai,the joint simulation of water quality and quantity is carried out,and the joint regulation scheme of water quality and quantity of Guanyinge and Shenwo reservoirs is determined by using the runoff series from1996 to 2007.Finally,taking the water quality of Tangmazhai section from 2015 to 2017 as an example,the rationality and feasibility of the joint regulation scheme of water quality and quantity are simulated and analyzed.The simulation results show that the combined operation scheme of Guanyinge and Shenwo reservoir can improve the water quality of Tangmazhai section of the downstream river to class IV standard and meet the water quality requirements of water functional areas on the premise of ensuring flood control safety and not affecting the guarantee rate of existing water supply target.