There is no necessary relationship between dams and pollution. Since dams generally affect the upper reaches of rivers, where there are fewer people and less pollution, serious pollution problems will not arise. Only if it is built in the middle reaches of the river and caters to relatively developed economic areas, water pollution problems will arise due to the slow flow of water caused by dams. For example, China's Three Gorges Project conducted long-term research on water pollution before construction, so it did not have obvious water pollution problems after completion.
Water refers to a vague concept. When we talk about water pollution, it can refer to community water pollution, river pollution, etc. The scope is relatively vague. A body of water is a systemth. XX lakes, XX river basins, etc. This is a relatively clear and relatively broad concept of water resources. Water pollution does not necessarily mean water pollution, but water pollution must be water pollution. Water pollution is an environmental problem that can be significant. or small.