Denison Beach Lake
Sac County, IowaView mapDirections
No nutrient or algae sampling on record from Iowa DNR for this lake.
- Impaired · Algal growth
- Public access
- Limited data
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Answers come straight from the public measurements and survey records on this page.
Denison Beach Lake in Sac County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported.
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Denison Beach Lake is a lake in Sac County, Iowa. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 2 public boat landings.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-08-27. Grade methodology: LakeQuality methodology.
What Denison Beach Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch2 documented ramps
Swimming conditions
No readingBacteria advisory
Based on E. coli testing, Denison Beach Lake frequently exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 14.6% of 103 samples across 7 seasons.
This is a historical summary of past testing, not a current condition — bacteria levels change quickly, especially after rain. Always check Iowa’s current beach and health-department advisories before swimming.
Whether Denison Beach Lake is safe to swim in today is a call for the Iowa Department of Natural Resources and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Denison Beach Lake
These are the measurements Iowa DNR publishes for Denison Beach Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data.
| Metric | Value | EPA condition class |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples |
Recreation & Access
- Ice House PointPublic
- Crescent Park DrivePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Denison Beach Lake
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.016 m/yr | 5 |
| Phosphorus | ↑ Improving | -10.3 µg/L/yr | 4 |
| Chlorophyll-a | ↑ Improving | -4.99 µg/L/yr | 5 |
EPA Impairment Status
Denison Beach Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IA 04-RAC-1134 · Official waterbody report · Matched by proximity (0.84 km)
Nearby Lakes in Sac County
Frequently asked questions about Denison Beach Lake
Where is Denison Beach Lake?
- Denison Beach Lake is a lake in Sac County, Iowa. Its water-quality measurements are published by Iowa DNR and shown on this page as reported.
What is the water quality of Denison Beach Lake?
- Denison Beach Lake in Sac County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported.
Is Denison Beach Lake safe to swim in?
- Based on E. coli testing, Denison Beach Lake frequently exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 14.6% of 103 samples across 7 seasons. That is a historical summary of past bacteria testing, not a current reading and not a swimming clearance. Bacteria levels can spike quickly after heavy rain, so whether Denison Beach Lake is safe to swim in today is a call for Iowa's water agency and the county health department; check their current beach advisories before you swim.
Are there boat ramps on Denison Beach Lake?
- Denison Beach Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Ice House Point, Crescent Park Drive. Public access is listed as yes.
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Where this data comes from
44 measurements from 1 monitoring station, 2021–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Iowa DNR Surface Water Monitoring Data
21IOWA_WQX44 samples · 2021–2024
Analytical methods
- 2130 B ~ Nephelometric Method
Monitoring station identifiers (1)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Named boat-access points from the USGS National Boat Ramps inventory