Jefferson County Lake Quality

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 recent nutrient and algae readings. The county-level summary describes that subset, not every water body listed. Most monitored lakes in Jefferson County carry favourable nutrient and algae readings for Colorado.

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. Chatfield Reservoir has the lowest nutrient and algae readings in the county.