Big Creek Lake
Polk County, Iowa885 acresView mapDirections
Nutrients and algae run well above the regional average.
- Hypereutrophic
- Impaired · Algal growth
- #9 of 12 in the county
- Public access
Big Creek Lake in Polk County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 2.6 ft visibility. Phosphorus: 80 µg/L. Chlorophyll-a (algae): 35.7 µg/L. Surface area: 885 acres.
- Clarity
- 2.6 ft
- Typical in September
- 74°F
- Area
- 885 acres
- Type
- Hypereutrophic
- Trend
- ↑ Improving
- Public access
- Yes
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Stays 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. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Big Creek Lake are listed below.
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Big Creek Lake is a 885-acre highly nutrient-loaded hypereutrophic 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. Compared to the 11 other monitored lakes in Polk County, Big Creek Lake ranks #9 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-09-30. Grade methodology: LakeQuality methodology.
Swimming Safety
Grade onlyBacteria A · advisory
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
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 (Algae-prone)
Very murky, less than 2.6 ft of visibility. Phosphorus 80 µg/L. Chlorophyll-a 35.7 µg/L. TSI 65. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.6 ft | Not graded |
| Phosphorus | 80 µg/L | Poor |
| Chlorophyll-a (Algae) | 35.7 µg/L | Poor |
| Trophic State Index (TSI) | 65 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Water Temperature
Big Creek Lake typically sits around 74°F at the surface in September. Summer average is about 77°F. 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 →
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 885 acres |
| Public Access | Yes |
No bathymetric survey has been published for Big Creek Lake, so its depth is not documented here.
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 |
| Phosphorus | ↑ Improving | -4.7 µg/L/yr | 4 |
| Chlorophyll-a | ↑ Improving | -3.38 µg/L/yr | 5 |
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.
County Ranking
Ranked #9 of 12 lakes in Polk County
Nearby Lakes With Higher Grades
Big Creek Lake holds Grade F. 2 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Polk County
Frequently asked questions about Big Creek Lake
Where is Big Creek Lake?
- Big Creek Lake is a lake in Polk County, Iowa. LakeQuality grades it F for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Big Creek Lake?
- Big Creek Lake in Polk County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 2.6 ft visibility. Phosphorus: 80 µg/L. Chlorophyll-a (algae): 35.7 µg/L. Surface area: 885 acres.
Is Big Creek Lake safe to swim in?
- 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. That works out to a bacteria swim-safety grade of A — a historical summary of past testing, not a current reading. Big Creek Lake has a water quality grade of F (Algae-prone). Bacteria levels can spike quickly after heavy rain, so always check Iowa's current beach and health-department advisories before you swim.
What is the water temperature of Big Creek Lake?
- Big Creek Lake typically sits around 74°F at the surface in September, from 40 EPA Water Quality Portal field readings (2010–2023). That is a typical value for the month, not a live reading.
Explore Big Creek Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
Species activity outlook by water temperature and season
Where to stay at Iowa's top lakes, each with its grade
Very high nutrients, dense algae, poor clarity
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Where this data comes from
187 measurements from 1 monitoring station, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Iowa DNR Surface Water Monitoring Data
21IOWA_WQX187 samples · 2020–2024
Analytical methods
- Unknown
- LAC 10-115-01-1F (UHL)
- Phosphorus by Colorimetry
- LAC 10-115-01-2B (UHL)
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
- In-Vitro Determination of Chlorophyll
- ISU modification of APHA 2130-B
- 2130 B ~ Nephelometric Method
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)