The scientists studied the water quality of Caohai Lake in Dianchi Lake over 10 years. They used a Water Quality Index to check pollution levels. Heavy metals were okay, dropping from 2004 to 2007, but got bad in 2007. The second index was worrisome, with the worst pollution in 2009. The third index was good, jumping between 3 to 32. Nutrients, like total nitrogen, and total phosphorus were key pollutants affecting the lake's water quality.