The scientists looked at the quality of water in rivers near Taihu Lake to understand how polluted they were. They measured different kinds of pollution in 29 rivers nearby and found that the ones in the northern heavily-polluted areas were the dirtiest. Overall, the pollution ranking was: worst in the north, then the west, followed by western Zhejiang Province, and eastern areas. Compared to the past decade, the water quality might be getting slightly better around the lake, but the inflowing rivers remain highly polluted. The researchers emphasized that reducing nitrogen entering the rivers is crucial for improving the water quality.