Oregon Lake Water Quality

Across {{stateName}}, 73 lakes carry an active water-quality grade spread over 22 counties. The underlying measurements come from {{agency}}, alongside federal programs and volunteer monitoring networks. About 33% of {{stateName}}'s lakes pull an A — 24 top-bracket waters. That high A-share comes mostly from the cold, deep, kettle-formed lakes in the north of the state, which buffer themselves against nutrient inputs.

Eutrophic conditions dominate — nutrient-loaded, productive, with algal pressure that shows up most years in late summer. These lakes tend to be shallow, agricultural-watershed, and over-warmed by the time July ends. Wallowa ranks highest on average county grade (A). Harney sits lowest. With only 22 counties in the state, the cross-county spread is narrower than the within-county spread for most lakes.