Big Creek Lake is a 885-acre productive, nutrient-rich eutrophic lake in Polk County, Iowa. Water quality is graded F based on 2 sampling years through 2024. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 11 other monitored lakes in Polk County, Big Creek Lake ranks #5 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-09-30. Grade methodology: LakeGrade methodology.
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Swimming Safety
Based on E. coli testing, Big Creek Lake never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 23 samples across 4 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.
Water Quality Grade: F, Very Poor
Very murky, less than 2.6 ft of visibility. Chlorophyll-a: 35.7 µg/L. Trophic State Index: 64.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.6 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 35.7 µg/L | F |
| Trophic State Index (TSI) | 64 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 885 acres |
| Public Access | Yes |
Where to stay near Big Creek Lake
Compare lakeside cabins, hotels, and vacation rentals near Big Creek Lake in Polk County, Iowa — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
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Fishing Big Creek Lake
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.02 m/yr | 5 |
| Chlorophyll-a | ↑ Improving | -3.38 µg/L/yr | 5 |
Recreation & Access
Water Temperature
Big Creek Lake averages about 77°F at the surface in summer, usually warmest in Jul (about 80°F) and coldest in May (about 63°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 40 field readings (2010–2023) via the EPA Water Quality Portal. See the full Big Creek Lake water temperature breakdown →
Location
County Ranking
Ranked #5 of 12 lakes in Polk County
Cleaner Lakes Within 30 Miles
Big Creek Lake holds Grade F. 2 nearby lakes hold higher grades.
- ATerra Park LakePolk County · 9.3 mi · Two grade letters higher (F → A)
- CLake PetockaPolk County · 16.2 mi · Two grade letters higher (F → C)
Nearby Lakes in Polk County
Explore Big Creek Lake across LakeGrade
More Iowa Lake Rankings
Other Grade F Lakes in Iowa
Eutrophic Lakes in Iowa
More records, surveys & data sources
Reservoir Info (USACE NID)
Big Creek Lake is a man-made reservoir impounded by the Big Creek Diversion Dam (completed 1970), built primarily for flood risk reduction on the BIG CREEK; gravity-type dam, 80 ft tall and 1,750 ft long.
- Surface area
- 885 ac
- Normal storage
- 7,600 ac-ft
- Max storage
- 27,500 ac-ft
- Drainage area
- 76 sq mi
- Hazard class
- High
- Owner
- USACE - Rock Island District
Source: USACE National Inventory of Dams, NID ID IA00014 · Operator website
EPA Impairment Status
Big Creek 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-UDM-1242 · Official waterbody report
Regulated Pollution Sources Nearby
4 EPA-permitted facilities operate within about 5 miles of Big Creek Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Polk City, City Of Water Treatment PlantPolk City · 1.7 mi away · NPDES IA0082384Recent violation
- Polk City, City Of StpPolk City · 2.1 mi away · NPDES IA0041939
- Jester Park #3-(New Lodge)Granger · 2.5 mi away · NPDES IA0076872
- Jester Park #2Granger · 2.5 mi away · NPDES IA0071803
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Grading methodology based on Metropolitan Council standards
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2024-09-30
Monitoring stations: 1