GIS and ordination techniques for studying influence of watershed characteristics on river water quality.

Landscape characteristics of twenty-eight sub-catchments within the Miyun reservoir watershed in Miyun County, northeast Beijing of China were examined to identify relationships with stream water chemistry. The influences of the entire catchment and 300 m buffer zone on water quality were compared using multiple regression analysis and redundancy analysis during three seasons. Results showed that strong seasonal differences in nitrate, nitrite and ammonium are observed whereas no difference in total phosphorus and conductivity. Landscape factors were significantly correlated to stream water quality. Residential area and stream density contributed markedly to river condition variability. Water quality was better explained by interactions with the landscape during and after rainy season. There was also a seasonal shift in the landscape factors that were the dominant explanatory variables. The relationships between landscape attributes and water quality on watershed scale were slightly different from those on riparian scale; however, landscape attributes may have stronger influences on water chemistry. [ABSTRACT FROM AUTHOR]