Grant County Lake Quality

Grant County's 48 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. 2 of those lakes carry an A–F grade. The county-level summary describes that subset, not every water body listed. The county's average grade is A — among the cleanest in Washington. 1 lakes pull an A on their own, and almost none fall into the D or F brackets.

Most of the county's monitored lakes are shallow — under 50 feet — which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed. Banks Lake (A) is the cleanest in the county.