Water Quality


Maine's water quality far exceeds the national average

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 (MDEP) and U.S. Environmental Protection Agency (EPA) on the water quality of Maine rivers, streams, and lakes. The proportion of water bodies achieving Maine’s Category 1 and 2 classifications are compared with U.S. water bodies receiving the EPA’s “good” classification. 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 amount of assessed water bodies, differing 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