Water chemical properties of Miyun Reservoir, Beijing and the main rivers flowing into the reservoir

This paper investigated and analyzed the water chemical properties of Miyun Reservoir,Beijing and the varied river runoff affected by forest vegetation in the Miyun Reservoir Watershed.The results showed that the concentrations of some elements in the rivers and creeks flowing into the Miyun Reservoir were not only related to the chemical composition of precipitation in open field,but also affected by the characteristics of local soil,vegetation and human factors.The water eutrophication pollution of Miyun Reservoir during the period of year 2003-2005 was more serious than those of the past 20 years.The pollution contribution from the Bai River Sub-watershed was the largest,which accounted for 46.20% of the Miyun Reservior;while that of the Chao River was the second by accounting for 30.02% of the reservoir;and the third was the Baimaguan River by accounting for 4.97% of the reservior.The concentrations of N and P in Chao River and Bai River were higher than those of Baimaguan River and Andamu River,but the situation was contrary for the element K.The above concentration differences might be caused by the variances in land use and fertilization.The waterhead-protection forests in the Miyun Reservoir play a key role in improving the water quality of precipitation and farmland surface flow.