A government report issued on Tuesday said China's current water quality is "not optimistic."

The Yellow, Songhua, Liaohe and Huaihe rivers are all slightly polluted, according to a report issued by the Ministry of Environmental Protection.

The report said that 25 percent of the 60 lakes and reservoirs monitored by the ministry have excessive amounts of algae.

The quality of coastal waters in the Yellow and South China seas is good, while that of the Bohai and East China seas is poor, the report said.

The report said seven of the country's nine most important bays have bad water quality, particularly Bohai and Hangzhou bays and the Yangtze River and Pearl River estuaries.