What is the cleanest lake in Colorado?

Pueblo Reservoir in Pueblo County has the cleanest nutrient and algae readings in Colorado, with 6.5 feet of measured water clarity.

How are these rankings calculated?

Nutrients and algae, total phosphorus, nitrogen, chlorophyll-a and turbidity, are read against EPA National Lakes Assessment 2022 condition classes for that lake’s ecoregion. Water clarity (Secchi depth) is measured and shown separately. Lakes without enough recent samples are listed without a condition class rather than ranked low. Source data comes from the EPA Water Quality Portal.

Cleanest Lakes in Colorado

Pueblo Reservoir in Pueblo County leads the rankings on measured clarity and nutrients and 6.5 ft of clarity. Below are the top 12 cleanest monitored lakes in Colorado, ranked on EPA nutrient and algae measurements.

Ranked List

#	Lake	County	Clarity	Phosphorus	Algae
1	Pueblo Reservoir	Pueblo	6.5 ft	15 µg/L	4.9 µg/L
2	Willow Creek Reservoir	Grand	3.9 ft	75.5 µg/L	2.4 µg/L
3	Wolford Mountain Reservoir	Grand	7.5 ft	13 µg/L	2 µg/L
4	Grand Lake	Grand	8.7 ft	14 µg/L	2.7 µg/L
5	Shadow Mountain Lake	Grand	7.9 ft	20 µg/L	5.1 µg/L
6	Blue Mesa Reservoir	Gunnison	11.5 ft	35 µg/L	3.9 µg/L
7	Dillon Reservoir	Summit	11.6 ft	46 µg/L	2.8 µg/L
8	Deweese Reservoir	Custer	5.2 ft	41.5 µg/L	13.5 µg/L
9	Windy Gap Reservoir	Grand	-	52 µg/L	3 µg/L
10	Horse Creek Outlet Lake	Weld	-	460 µg/L	27.6 µg/L
11	Stagecoach Lake	Routt	-	50 µg/L	-
12	Prospect Lake	Weld	-	300 µg/L	42.5 µg/L

Ranked List

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