Temporal Variation of Water Quality and Driving Factors in Yanghe Watershed of Zhangjiakou
洋河流域张家口段河流水质演化及驱动因子分析

Yanghe is an important water source for Guanting Reservoir, which once supplied the Beijing city with drinking water, industrial process water and water-use in landscape. Based on the data of water quality monitored by Yanghe watershed monitoring stations from 1992 to 2009, 11 pollutants were selected for analysis. The trends of changes in water quality were figured out, and the major pollutants and driving factors were measured by the integrated standard index and grey correlation analytical methods. The results showed that there were two stages of water quality change in Yanghe watershed of Zhangjiakou. Firstly, the water was polluted seriously but recovered rapidly from 1992 to 1996.Secondly, although light pollution occurred in the watershed from 1997 to 2009, the pollution factors were still above the limits. The main pollution factors are ammonia nitrogen, petroleum, permanganate index,BOD5, Cr6+ and Cd. The main driving factor of water quality is the change of land use type, and the agricultural land showed less impact on water quality than the industrial land.