Continuously Export Modeling Of Phosphorus For Heihe Watershed

The problem of eutrophication is more and more serious in many countries including China. And it has been one of the primary water environmental problems today. The nutrient entering into rivers with runoff is one of the main reasons of eutrophication. The research on non-point source pollution based on single event is comparatively mature, but there are few studies on continuously modeling in China. So continuously modeling phosphorus export at a watershed scale has important significance to the control and management of eutrophication in China.Taking Heihe watershed, the primary tributary of Weihe river, as an example, the main contents and results of this paper are as follows:1. The data of rain, evaporation, runoff and sediment concentration from 1981 to 1990 in Heihe watershed are partitioned as same time interval by adopting input format of hydrological almanac.2.Aimed at natural and geographic conditions of Heihe river basin, the XinAnJiang hydrological model is used to calculate runoff yield, the Inverse-Gauss distribution instantaneous unit hydrograph is adopted to calculate flow concentration during rain time, while the linear reservoir routing method is applied to calculate flow concentration in rainless time. Then, the parameters are analyzed and calibrated. The total efficiency of the runoff model from 1981 to 1990 is 61.3%, and the main reasons of the low modeling precision were analyzed also.3. Using the experiential correlation method, sediment yield is calculated. Theresults show that the pass percent of annual sediment discharge and the model efficiency coefficient (DC) are about 50%.The low value of the relative coefficient and the low modeling precision to runoff are the two main reasons affecting the calculation precision of the sediment.4.Considering the data conditions in Heihe watershed, the part of the phosphorous transport and export calculation of Viney's model is simplified. And then, the parameters value are analyzed and calibrated. The results from 1981 to 1990 show that the total annual phosphorus load is accordant with the universal law of phosphorous loss, and the amount of the load magnitude is reasonable. But precision of the model is relative low, it is necessary to modify and improve the model.5. All model calculation is completed with Matlab programs. When the hydrological data are input, the model can achieve continuously modeling the total phosphorus output of Heihe river basin. The research of this paper has significant meanings for the control and management of phosphorous loss in Heihe river basin.