Scientists developed methods to clean up the rivers flowing into Lake Taihu troubled by pollution. They studied 15 rivers entering the lake to suggest ways to control pollution and predict ways to reduce harmful substances going into the lake. By May 2009, changes made to 9 out of 15 rivers helped improve their water quality from very bad to better. The modifications also decreased the lake’s eutrophication level (a condition causing too many nutrients) from medium to light. This work marked a good start in enhancing Lake Taihu’s water quality.