Yakima County Lake Quality

Yakima County's 23 monitored lakes fall in the moderate-density bracket for Washington. The county-level average smooths over real differences — a single agricultural watershed near the southwest corner can pull the average down even if the rest of the county runs clean. 1 of those lake carry an A–F grade. The county-level summary describes that subset, not every water body listed. Yakima County averages to a C. The distribution behind that average matters more than the letter: a few stressed lakes versus many decent ones can produce the same average as the inverse.

The county's lakes lean shallow, which makes the grades sensitive to wind, sediment-resuspension, and any nutrient inputs from the watershed. The cleanest lake on the books is Rimrock Reservoir (C); the most-stressed is Rimrock Reservoir (C).