The scientists studied water pollution in Zhegao River near Chao Lake for four years. They found that the upper part of the river had decent water quality but too many nutrients from farms. The middle section, near Zhegao town, was very polluted due to untreated sewage. Downstream, the river was moderately polluted with various sources like farms and urban waste. They observed that nitrate levels were high in winter-spring, while total phosphorus was higher in summer, putting Chao Lake at risk. To save Zhegao River, several actions are needed to clean up the water.