Dianchi Lake's water quality has worsened, reaching very poor levels due to pollution mainly from sewage and agriculture. The lake has become excessively rich in nutrients, causing rapid growth of harmful substances that harm the ecosystem. Pollution levels have increased over the past decade, particularly in the Waihai section, with phosphorus playing a big role in the lake's decline. Treatment efforts have been more focused on direct sources of pollution near Caohai and less on non-point sources elsewhere. To tackle the lake's problems, it is crucial to strengthen efforts to control non-point pollution, restore the lake's ecosystem, and manage it effectively.