Boulder County Lake Quality

Boulder County's 36 monitored lakes fall in the moderate-density bracket for Colorado. 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. No lake in Boulder County has enough sampling behind it for an A–F grade yet. The 36 monitored lakes below carry whatever clarity, phosphorus, and chlorophyll-a measurements exist.

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.