Spatio-temporal dynamics of nutrients in the upper Han River basin, China

The upper Han River basin with an area of approximately 95,000 km², is the water source area of the Middle Route of China's South to North Water Transfer Project. Thus, water quality in the basin's river network is of great importance. Nutrients including dissolved inorganic nitrogen (DIN), NO₃⁻-N, NH₄⁺-N, and dissolved phosphorus (DP) were analyzed in 41 sites during the period of 2005–2006. Cluster analysis (CA), analysis of variance (ANOVA) and general linear models (GLM) were performed to explore their spatio-temporal variations in the basin. The results revealed that the DIN, NO₃⁻-N and NH₄⁺-N increased over the 2 year study period, and their concentrations in the wet season was higher than those in the dry season. The seasonal variation in nitrogen was strongly associated with seasonal pattern of precipitation and there was a negative relationship between DP concentration and river flow. Cluster analysis indicated high nutrient contents in the urban and agricultural production areas. The research will help articulate water resource management strategy for the interbasin water transfer project.