Lakes and their drainage basins provide important ecosystem services and natural resources to support human development. However, many rivers and lakes have become polluted and eutrophied. Haihe Basin is one of the largest river basins of China, facing serious water pollution and water shortage. There are more than 1000 reservoirs and natural lakes in Haihe Basin. In this thesis, I choose Guanting reservoir and Baiyangdian lake in Haihe Basin as case studies. The main objective of this research is to improve our understanding of nutrient flows from land to two lakes in the Haihe Basin, and possibilities to reduce this pollution in the future.