Hardin County Lake Quality
Iowa, 4 lakes, average grade F (Algae-prone)
Hardin County has 4 monitored lakes — a thin enough sample that one or two stressed lakes can move the county average noticeably. Use the per-lake pages below for what actually matters. 2 of those lakes carry an A–F grade. The county-level summary describes that subset, not every water body listed. The county average is F — the most-stressed bracket in our rubric. Most monitored lakes here show persistent nutrient loading and algal pressure.
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. Upper Pine Lake (F) is the cleanest in the county.
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Quick Answers for Hardin County
Planning a trip? Check special fishing regulations for Upper Pine Lake — or check the official Iowa fishing regulations.
All Lakes in Hardin County
4 lakes · 2 graded, 2 not rated2 graded lakes · 2 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| 1 | FUpper Pine LakeHardin | F | 1.3 ft | 112 µg/L | 66.7 µg/L | No recent samples | ✓ Public |
| 2 | FLower Pine LakeHardin | F | 1.3 ft | 187 µg/L | 73.5 µg/L | No recent samples | ✓ Public |
| NRPine Lake South BeachHardin | NR | 1.4 ft | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRLpinelk T LakeHardin | NR | 1.3 ft | No recent samples | No recent samples | No recent samples | Not recorded |
NR = not rated: there is not enough recent sampling to support a letter. That is EPA Integrated Reporting Category 3 (insufficient information), not a failing grade. How grading works.
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Other Counties in Iowa
See how Hardin County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all United States (49 states), Canada (Ontario, Québec, Nova Scotia, British Columbia and Newfoundland and Labrador), and 38 other country hubs..
Source: EPA National Aquatic Resource Surveys, 2026.