What is the cleanest lake in Iowa?

West Okoboji Lake in Dickinson County has the cleanest nutrient and algae readings in Iowa, with 15.7 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 Iowa

West Okoboji Lake in Dickinson County leads the rankings on measured clarity and nutrients and 15.7 ft of clarity. Below are the top 50 cleanest monitored lakes in Iowa, ranked on EPA nutrient and algae measurements.

Ranked List

#	Lake	County	Clarity	Phosphorus	Algae
1	West Okoboji Lake	Dickinson	15.7 ft	20 µg/L	2.3 µg/L
2	Dale Maffitt Reservoir	Dallas	9.8 ft	20 µg/L	2.1 µg/L
3	Blue Pit Lake	Cerro Gordo	17.1 ft	20 µg/L	2.4 µg/L
4	Ada Hayden Heritage Park Lake	Story	6.8 ft	19 µg/L	5.2 µg/L
5	Little Sioux Park Lake	Woodbury	5.7 ft	19 µg/L	5.7 µg/L
6	Rudd Lake	Floyd	8.1 ft	14 µg/L	4.5 µg/L
7	Slipbluff Lake	Decatur	9 ft	17.5 µg/L	4.5 µg/L
8	Lacey Keosauqua Lake	Van Buren	7.1 ft	21.5 µg/L	4.7 µg/L
9	Yenruogis Pond	Keokuk	9.9 ft	21 µg/L	6.2 µg/L
10	Sand Lake	Marshall	6.4 ft	25 µg/L	3.6 µg/L
11	Terra Park Lake	Polk	11.5 ft	20 µg/L	4.7 µg/L
12	Storm Lake Max Depth	Buena Vista	1.7 ft	123.5 µg/L	11 µg/L
13	Arrowhead Lake	Sac	5.6 ft	26 µg/L	7.1 µg/L
14	Kent Park Lake	Johnson	4.8 ft	25 µg/L	11.4 µg/L
15	Mariposa Lake	Jasper	5.1 ft	31 µg/L	8.9 µg/L
16	Mormon Trail Lake	Adair	6.2 ft	25 µg/L	9.7 µg/L
17	Newell Pit Lake	Buena Vista	4.1 ft	37 µg/L	11.9 µg/L
18	Bob White Lake	Wayne	0.6 ft	264 µg/L	10.1 µg/L
19	Willow Lake	Harrison	4.8 ft	35 µg/L	9.5 µg/L
20	Poll Miller Park Lake	Lee	5.9 ft	28 µg/L	7.7 µg/L
21	Lake Minnewashta	Dickinson	2.8 ft	47 µg/L	19 µg/L
22	Upper Gar Lake	Dickinson	3.9 ft	52.5 µg/L	13.1 µg/L
23	Railroad Lake	Scott	5.1 ft	44.5 µg/L	8.3 µg/L
24	Big Spirit Lake	Dickinson	5.5 ft	55 µg/L	16.3 µg/L
25	Mitchell Lake	Black Hawk	2.3 ft	40.5 µg/L	18.7 µg/L
26	Lost Grove Lake	Scott	3.9 ft	31 µg/L	15.8 µg/L
27	Blue Grass Lake	Scott	4.5 ft	63 µg/L	12.7 µg/L
28	Oldham Lake	Monona	5.1 ft	46 µg/L	8.5 µg/L
29	Rathbun Lake	Appanoose	3 ft	48 µg/L	15.3 µg/L
30	Green Belt Lake	Black Hawk	2.4 ft	57 µg/L	18.6 µg/L
31	Green Castle Lake	Marshall	4.6 ft	59 µg/L	6.9 µg/L
32	Lake Petocka	Polk	3.3 ft	39.5 µg/L	9.3 µg/L
33	Lake of the Hills	Scott	5.1 ft	53 µg/L	16.8 µg/L
34	Lambach Lake	Scott	7.9 ft	63 µg/L	5.1 µg/L
35	Stolley Pit Lake	Clay	2.7 ft	48 µg/L	17.3 µg/L
36	Thomas Mitchell Lake	Polk	3.3 ft	87 µg/L	13.2 µg/L
37	Lost Island Lake	Palo Alto	2.6 ft	68 µg/L	19.1 µg/L
38	Nodaway Lake	Adair	2.8 ft	57 µg/L	27.6 µg/L
39	Clear Lake	Cerro Gordo	2.1 ft	52 µg/L	26.4 µg/L
40	Pleasant Creek Lake	Linn	3.6 ft	38 µg/L	26.5 µg/L
41	Hooper Pond Lake	Warren	2.5 ft	61 µg/L	25.1 µg/L
42	Lower Gar Lake	Dickinson	2.6 ft	71.5 µg/L	20.7 µg/L
43	Manteno Lake	Shelby	2.7 ft	138.5 µg/L	28.3 µg/L
44	Lake Cornelia	Wright	2.5 ft	37 µg/L	20.1 µg/L
45	Hawthorn Lake	Mahaska	2.4 ft	60 µg/L	27.5 µg/L
46	Yellow Smoke Lake	Crawford	3 ft	56.5 µg/L	21.6 µg/L
47	Easter Lake	Polk	2.9 ft	49.5 µg/L	22.8 µg/L
48	Three Mile Lake	Union	2.7 ft	43 µg/L	28.4 µg/L
49	East Okoboji Lake	Dickinson	3.9 ft	56 µg/L	25.3 µg/L
50	Lake Macbride	Johnson	2.9 ft	59 µg/L	28.5 µg/L

Ranked List

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