Effect Of Forest Vegetation On The Non-point Source Pollution Of Surface Runoff In Miyun Reservoir Watershed, Beijing

Miyun reservoir, an important water source of Beijing, supplies about 70 percent drinking water to Beijing. Currently, some research on the drainage area show that water quality of the reservoir has been contaminated badly in which the nitrogen and phosphorus pollution is the severest. The upper water is the root of the pollution of the water quality of Miyun reservoir. Most of the drainage area are covered by forest vegetation, however, the research about the effect of forest vegetation on the non-point pollution of surface runoff are rarely studied. Therefore, this paper mainly aims at doing research on the effect of forest vegetation on the non-point pollution by investigating, monitoring and analyzing, which can provide the basis for the control of the non-point pollution of Miyun reservoir.The method of the comparison of different types of foresty vegetation was used. The content of TN and TP in the branches of broad leaved forest, coniferous forest, fresh fruit forest, dry fruit forest and shrubbery were compared. Artificial rainfall was used to monitor locust forest slope runoff process. The method of the comparison of different runoff areas was used. Seven slope runoff areas were built in the east of Miyun reservoir, one of which was bare surface regarded as the background reference, and the vegetation types of the rest are different. By doing research on the background information, monitoring rainfall process and runoff yield of each slope runoff area, testing consistency of TN and TP of surface runoff, calculating the amount of TN and TP of runoff, comparing with the amount of TN and TP of the bare surface, the difference of various forest vegetation types on controlling the surface runoff non-point source pollution was concluded.Results showed that Robinia pseudoacacia forest has the best result on the effect of water and soil conservation, while Vitex chinensis Mill forest has the worst result. The consistency of TN and TP of Pinus tabulaeformis are more than that of other runoff areas'respectively. On the effect of controlling surface runoff TN, sizing down as Robinia pseudoacacia forest, grassland, Rhus typhina forest, Pinus tabulaeformis and Robinia pseudoacacia mingled forest, Pinus tabulaeformis forest, and Vitex chinensis Mill forest. On the effect of controlling surface runoff TP, sizing down as Robinia pseudoacacia forest, grassland, Rhus typhina forest, Pinus tabulaeformis and Robinia pseudoacacia mingled forest, Vitex chinensis Mill forest and Pinus tabulaeformis forest.