Sac County Lake Quality
Iowa, 3 lakes, average grade B (Good)
Sac County has 3 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. 1 of those lake carry an A–F grade. The county-level summary describes that subset, not every water body listed. The county-wide average lands at B — solid water quality with most lakes carrying clear summer transparency and low-to-moderate phosphorus.
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. Arrowhead Lake (B) is the cleanest in the county.
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Quick Answers for Sac County
Planning a trip? Check special fishing regulations for Arrowhead Lake — or check the official Iowa fishing regulations.
All Lakes in Sac County
3 lakes · 1 graded, 2 not rated1 graded lake · 2 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| 1 | BArrowhead LakeSac | B | 5.6 ft | 26 µg/L | 7.1 µg/L | No recent samples | ✓ Public |
| NRDenison Beach LakeSac | NR | No recent samples | No recent samples | No recent samples | No recent samples | ✓ Public | |
| NRBlack Hawk Beach LakeSac | NR | No recent samples | No recent samples | No recent samples | No recent samples | ✓ Public |
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.
Lake Match
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Other Counties in Iowa
See how Sac 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.