Simulation Of Water Environment In The Luxi River Basin Based On Multi-coupling Model

In recent years,with the rapid development of urbanization in the Tianfu New Area,the water environment and ecological problems of the Luxi River Basin have become increasingly complex.In order to improve the water environment of the Luxi River Basin and protect and restore the ecosystem,based on the current situation of the water environment with high concentrations of ammonia nitrogen（NH₃-N）and total phosphorus（TP）,five types of water environment management and ecological restoration measures are proposed.Use basin hydrological model（SWAT model）coupled with hydrodynamic water quality model（HEC-RAS model）to establish a water environment model for the Luxi River Basin,and quantitatively predict the effect of five types of measures on the improvement of water environment quality under two working conditions.The river water environment management,protection and sustainable development provide technical support.The main conclusions of this research are as follows:（1）The current water quality of the Luxi River is poor.The Yujiantan section and Chuanxin Bridge section are in the poor V and V categories except for a few months.The water quality throughout the year is poor.The main pollutants exceeding the standard are NH3-N and TP.（2）In 2015,the non-point source pollution load in the Luxi River Basin was higher than that of point source pollution;The total contribution rate of pollutants entering the river is ranked as rural life>urban runoff>agricultural runoff>free-range livestock>urban life>industrial pollution;The ranking of the contribution rate of NH3-N pollutants entering the river is rural life>urban runoff>agricultural runoff>free-range livestock>urban life>industrial pollution;the ranking of the contribution rate of TP pollutants entering the river is rural life>urban runoff>urban life>Free-range livestock>farmland runoff>industrial pollution.（3）Through on-site investigation and data collection,the SWAT model database is constructed,and the water volume,pollutant concentration and other information simulated by the model are transmitted to realize the coupling between the SWAT model and the HEC-RAS model.Through the calibration and verification of model parameters,the coupling effect between models is good.（4）Based on the multi-coupling water environment model of the Luxi River Basin,the analysis of the spatial distribution of runoff and pollution in the watershed found that the areas with the largest amount of surface runoff are mainly concentrated in the western,central and southern parts of the Luxi River Basin;NH₃-N and TP are produced in the watershed The most abundant places are concentrated in the southwest and northeast.（5）The five types of water environment treatment and ecological restoration measures have significant reduction effects on pollutants.The reduction rates of NH3-N and TP have reached 95%and 93%.（6）Establishing a basin water environment model to simulate the Luxi River Basin,through analysis of the model results,it can be found that:（1）The upstream water quality is particularly critical to the improvement of the Luxi River Basin.（2）The water quality of each important assessment section is above 83%under the two working conditions.The period when the water quality is not up to the standard is the dry period.Therefore,it is recommended to implement the ecological water replenishment project during the dry period.