Grays Lake
Polk County, IowaView mapDirections
Nutrients and algae run well above the regional average.
- Hypereutrophic
- Impaired · Algal growth
- #10 of 12 in the county
- Public access
Grays Lake in Polk County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 1.6 ft visibility. Phosphorus: 103 µg/L. Chlorophyll-a (algae): 46.5 µg/L.
- Clarity
- 1.6 ft
- Typical in September
- 73°F
- Type
- Hypereutrophic
- Trend
- ↓ Declining
- Public access
- Yes
Stays via Stay22
Stays near Grays Lake
Compare lakeside cabins, hotels, and vacation rentals near Grays 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 Grays Lake are listed below.
Top-rated places to stay near Grays Lake
Prices for Sep 11–13, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Iowa’s top lakes →
Watch Grays Lake’s letter
Email me if this lake’s grade moves. Grades stay free.
Or email
Free interactive depth-contour map of Grays Lake, reaching a maximum surveyed depth of 12 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
Grays Lake is a 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 declining over recent sampling years. Limited fish-species data available. Public access is available. Compared to the 11 other monitored lakes in Polk County, Grays Lake ranks #10 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-09-18. Grade methodology: LakeQuality methodology.
Swimming Safety
Grade onlyAlgae risk
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.
The F is nutrients and algae, not a swimming clearance. Grays Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, turbidity. Check local advisories before you swim.
Water Quality Grade: F (Algae-prone)
Very murky, less than 1.6 ft of visibility. Phosphorus 103 µg/L. Chlorophyll-a 46.5 µg/L. TSI 70. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.6 ft | Not graded |
| Phosphorus | 103 µg/L | Poor |
| Chlorophyll-a (Algae) | 46.5 µg/L | Poor |
| Trophic State Index (TSI) | 70 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Water Temperature
Grays Lake typically sits around 73°F at the surface in September. Summer average is about 79°F. Usually warmest in Jul (about 82°F) and coldest in Sep (about 73°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 16 field readings (2018–2026) via the EPA Water Quality Portal. See the full Grays Lake water temperature breakdown →
Fishing Grays Lake
Water Quality Trend: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.112 m/yr | 5 |
| Phosphorus | ↓ Declining | +15.3 µg/L/yr | 5 |
| Chlorophyll-a | ↓ Declining | +22.9 µg/L/yr | 5 |
EPA Impairment Status
Grays Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit IA 04-RAC-1118 · Official waterbody report
Regulated Pollution Sources Nearby
10 EPA-permitted facilities operate within about 5 miles of Grays Lake under Clean Water Act (NPDES) discharge permits. 6 facilities have a reported Clean Water Act violation in the past three years.
- Des Moines Tce Superfund SiteDes Moines · 0.7 mi away · NPDES IA0069671Recent violation
- Iowa Methodist Medical CenterDes Moines · 1.3 mi away · NPDES IA0052446Recent violation
- Bituminous Materials And Supply, LpDes Moines · 2.2 mi away · NPDES IA0073172Recent violation
- Mercyone Des Moines Medical CenterDes Moines · 2.2 mi away · NPDES IA0081477Recent violation
- Iowa Lutheran HospitalDes Moines · 2.7 mi away · NPDES IA0052438Recent violation
- Archer Daniels Midland CompanyDes Moines · 4.9 mi away · NPDES IA0072958Recent violation
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 #10 of 12 lakes in Polk County
Nearby Lakes With Higher Grades
Grays Lake holds Grade F. 3 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 Grays Lake
Where is Grays Lake?
- Grays 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 Grays Lake?
- Grays Lake in Polk County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 1.6 ft visibility. Phosphorus: 103 µg/L. Chlorophyll-a (algae): 46.5 µg/L.
Is Grays Lake safe to swim in?
- The F is nutrients and algae, not a swimming clearance. Grays Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, turbidity. Check local advisories before you swim.
What is the water temperature of Grays Lake?
- Grays Lake typically sits around 73°F at the surface in September, from 16 EPA Water Quality Portal field readings (2018–2026). That is a typical value for the month, not a live reading.
Explore Grays Lake across LakeQuality
More Iowa Lake Rankings
Other Grade F Lakes in Iowa
Hypereutrophic Lakes in Iowa
Where this data comes from
64 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_WQX64 samples · 2020–2024
Analytical methods
- Unknown
- Phosphorus by Colorimetry
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
- In-Vitro Determination of Chlorophyll
- ISU modification of APHA 2130-B
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)