Introduction to lake surface pollution: At the end of the last century, the number of whooper swans that came to Swan Lake to inhabit Swan Lake every year was about 6,000. Later, due to environmental pollution, the number of whooper swans coming here to overwinter decreased year by year, reaching a minimum of 1,200 in 2002. In order to solve the problem of water pollution, the local government cleaned up the silt at the bottom of the lake and planted macrophylla, a favorite food of swans, on the bottom of the lake. Not only that, in order to further optimize the environment here, the Rongcheng Municipal Government closed the landfill near Swan Lake, built three sewage treatment plants, and also carried out dredging and desilting of two nearby rivers. In addition, Chengshanwei Town has also established a Wildlife Protection Association and arranged more than 20 full-time personnel to conduct full-day patrols in areas where swans roam. When the swans have difficulty finding food, the staff will regularly feed them food so that the swans can survive better here.