Chouteau County Lake Quality

Chouteau County's 20 monitored lakes fall in the moderate-density bracket for Montana. 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. The county average is F — the most-stressed bracket in our rubric. Most monitored lakes here show persistent nutrient loading and algal pressure.

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. Boneau Reservoir (F) is the cleanest in the county.