Water Quality


In 2022, Maine maintained its excellent water quality rating.

No significant movement since the last available data

Benchmark: The percentage of Maine’s assessed water bodies classified as Categories 1 or 2 will be maintained over time.

Overview Fig. A


This measure is based on reports by the Maine Department of Environmental Protection and U.S. Environmental Protection Agency (EPA) on the water quality of Maine rivers, streams, and lakes. The proportion of water bodies achieving Category 1 and 2 (“good”) classifications are compared to the rest of the U.S. Maine’s rivers, lakes, and streams provide drinking water and support ecosystems. They are part of the natural environment that supports tourism.

Since 2006, Maine’s water quality has been very high, with 95% of rivers and streams and 91% of lakes achieving Category 1 or 2 in 2022. Nationally, just 31% of U.S. rivers and streams, and 19% of the lakes, were rated “good.” The sharp recent drop in U.S. quality has many causes, including a significant increase in the number of assessed water bodies, Differing assessment methods across states, and actual declines in water quality.


Fig. A

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Water Bodies Rated Category 1 or 2 ("Good")

Maine Department of Environmental Protection