Multi-scale approaches for solving nutrient problems in a Chinese watershed

Rapid economic development in China has fueled use of fertilizers, which have combined with existing animal and human waste to create severe problems with nutrient pollution, including cyanobacterial blooms in lakes and reservoirs.  A large, multi-institutional investigation is being developed to solve nutrient problems in the Tiaoxi watershed, which drains into the lake Taihu in eastern China.  Agricultural and urban sources of nutrients originate from complex landscapes, with headwaters in the mountains and the lower river flowing through a highly altered, low gradient delta before reaching Taihu.  A great effort has been put into organization of the project for integration of watershed features and models to understand sources of non-point pollution.  In-situ water sampling data and watershed characteristics are used as input to a biogeochemical model (DNDC-DeNitrification and DeComposition), integrated with statistical models, to understand the spatial and temporal dynamics of the eutrophication and major sources of nutrients within the watershed. Because of the spatial and annual variability in bloom development, historic analysis of satellite images as well as measured current conditions are being used to quantify relationships between algal blooms and nutrient concentrations. Thus measurements and modeling at multiple scales are needed to solve these problems.