Study On Numerical Model Of Improvement Of Non-point Source Pollution In The Upper Reaches Of The Yanghe Reservoir

Non-point source pollution has the characteristics of randomness,universality,hysteresis,fuzziness and latency,and it is difficult to research,control and formulate management guidelines.Based on the upstream watershed of Yanghe reservoir,this paper established a numerical model of non-point source pollution control in the upper reaches of Yanghe reservoir.Getting the pollutant diminishing amount at the reservoir entrance under different guarantee rate of rainfall,and proposing a controlling scheme of the entrance of the reservoir based on the research result.The upper reach of Yanghe reservoir is divided into four drainage basins includes Dongyang river,Xiyang river,Miwu river,Maguying river,and the four basins are divided into 237 sub-basin.In this paper,the pollutants in upper reach of Yanghe reservoir are classified by its characters in different stages of migration diffusion.The non-point source pollutants before and after source management is calculated in villages by output factor model.Simulating village range by Tyson polygon method,and according to the relative position between the village and the range of sub basin,distributing the pollutants to sub basin of the village,then,getting the calculation results of pollutants in each sub basin.The calculation results were analyzed in order to explore the main factors of formation of different pollutants.For the classification of sub basin,this paper deal with the use of commercial software to break the traditional way,according to the confluence relation of upstream watershed of Yanghe reservoir watershed,innovatively put forward the classification method of sub basin.According to the laws of runoff yield and pollutants migration and diffusion created rainfall confluence model and pollutants diffusion model,and then using Fortran language program for model parameter calibration and verification,the verification results show that the calculated results of model are approximately consistent with the measured values.Then,the model is used to calculate the confluence flow,out flow and the relative pollutants concentration in every sub basin under the conditions of all kinds of guarantee rate of rainfall.By comparing the concentration of pollutants and storage reservoir pollutants carrying capacity,the elimination amount of various pollutants before storage is obtained under various guarantee rates.It can be seen from the calculation of non-point source pollution results that pollutant generation is closely related to human activities,and the more people,the village distribution is more intensive,the amount of pollutants produced by the greater,and the main pollution source is livestock excreta.Through the calculation of rainfall runoff model and pollutant migration and diffusion model analysis showed: under the condition of higher guarantee rate and smaller rainfall,the water yield of sub basin is less,but the concentration of pollutants become higher,the pollution subduction amount is also larger.According to the simulation results,the pollution control scheme of upstream of Yanghe reservoir is to arrange pre reservoir and constructed wetland on the inlet of the reservoir,so as to make the pollutant concentration reach?grade water quality standard.