Dianchi Lake, the eighth largest lake in China, is returning to its old self as it undergoes rehabilitation that followed serious pollution caused by industrial, agricultural and domestic wastes. 

Officials say the lake water, which is located in Kunming City, southwest China's Yunnan Province, has seen major improvement such that it can again be used for agricultural and industrial purposes.

In the 1980s, wastewater containing nitrogen, phosphorus and other harmful substances had been discharged into the lake causing a massive outbreak of blue-green algae and the disappearance of about 80 percent of fish species.

To deal with the pollution, central government and provincial authorities implemented a series of programs to rebalance the lake's oxygen levels and get rid of the algae. An announcement by The Ministry of Ecology and Environment said the water quality of Dianchi Lake was now the best in the past 30 years. 

The China State Bureau of Technical Supervision classifies groundwater quality in five categories, from the best, Grade I, to the worst, Grade V. In the 1990s, Dianchi Lake was categorized at Grade V.

The newest data reveals that the Caohai and Waihai areas of the lake have improved to Grade IV, which is suitable for agricultural and industrial use. The water can be also used for drinking but after proper treatment. 

Dianchi Lake is named as "Sparkling Pearl Embedded in a Highland," a freshwater fault lake 1,886.5 meters above sea level. Every winter during the lake's annual seagull season, thousands of Siberian seagulls migrate to Kunming, dubbed China's “spring city”, to spend their winter.