Polk County Lake Quality
Iowa, 12 lakes, average grade D (Poor)
Only 12 lakes in Polk County carry an active grade. The county-level summary is therefore representative of those specific lakes, not necessarily of every water body in the county. The county-wide average grade is D — water quality issues are persistent across most of the monitored basins. 4 lakes fall into the F bracket outright.
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. Terra Park Lake (A) is the cleanest in the county.
Quick Answers for Polk County
Planning a trip? Check special fishing regulations for Terra Park Lake — or check the official Iowa fishing regulations.
All Lakes in Polk County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Terra Park Lake | A | 11.5 ft | - |
| 2 | Lake Petocka | C | 3.3 ft | - |
| 3 | Thomas Mitchell Lake | D | 3.3 ft | - |
| 4 | Easter Lake | D | 2.9 ft | - |
| 5 | Big Creek Lake | F | 2.6 ft | - |
| 6 | Grays Lake | F | 1.6 ft | - |
| 7 | Blue Heron Lake | F | 2.2 ft | - |
| 8 | Fort des Moines Park Pond | F | 2.8 ft | - |
Other Counties in Iowa
See how Polk County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 15 states.
Where to stay near Polk County
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Source: EPA National Aquatic Resource Surveys, 2026.