Grays Lake is a lake in Polk County, Iowa. Its water-quality measurements are published by Iowa DNR and shown on this page as reported.

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.

Can I fish at Grays Lake?

Public access to Grays Lake is listed as yes on the lake record. Seasons, size and bag limits, and whether you need a license are set by Iowa's fish and wildlife agency, so check its current regulations before you go.

Grays Lake

Polk County, IowaView map Directions

Iowa DNR publishes the water-quality measurements for Grays Lake. Here is what has been measured.

Clarity

1.6 ft

Typical for Iowa

Secchi · sampled 2024

Phosphorus

103 µg/L

Typical for Iowa

Measured by Iowa DNR

Chlorophyll-a

46.5 µg/L

Typical for Iowa

Measured by Iowa DNR

Water temp

~73°F

Typical for Sep · EPA WQP

Type

Hypereutrophic

Trophic class

Trend

Worsening

5 years of samples

Hypereutrophic
Impaired · Algal growth
Public access

See the measurements Directions Where to stay

Grays Lake in Polk County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 1.6 ft visibility. Phosphorus: 103 µg/L. Chlorophyll-a (algae): 46.5 µg/L.

Loading map…

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. 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. Methodology: how these readings are compared.

If you are planning to stay, you can search lake houses and cabins around Grays Lake on Vrbo, or look for a hotel room near the lake on Booking.com or Expedia.

Swimming conditions

Readings only

Recreation use not supported

Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.

Nutrient and algae readings are 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.

Whether Grays 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.

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Water quality measurements for Grays Lake

These are the measurements Iowa DNR publishes for Grays Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.

Very murky, less than 1.6 ft of visibility. Phosphorus 103 µg/L. Chlorophyll-a 46.5 µg/L. TSI 70.

Water quality readings
Measure	Reading	Where it sits
Water clarity (Secchi depth)	1.6ft	Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer.
Total phosphorus	103µg/L	Poor GoodFairPoor
Chlorophyll-a (algae)	46.5µg/L	Poor GoodFairPoor
Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a.	70	Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic

Very high nutrients, dense algae, poor clarity

Ask about Grays Lake

Answers come straight from the public measurements and survey records on this page.

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.

Jan

Feb

Mar

Apr

May

75°

Jun

82°

Jul

Aug

73°

Sep

Oct

Nov

Dec

Column height runs from this lake’s coldest month (73°F) to its warmest (82°F).

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 →

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 readings cover nutrients and algae, not lodging. Cabins and rentals around Grays Lake are listed below.

Top-rated places to stay near Grays Lake

Prices for Oct 23–25, 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.

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Fishing Grays Lake

→ Grays Lake fishing regulations (limits, seasons, special rules)

Water Quality Trend: Worsening

Based on 5 years of monitoring (2020–2024).

Water clarity
Worsening
5 years
Phosphorus
Worsening
+15.3 µg/L/yr5 years
Chlorophyll-a
Worsening
+22.9 µg/L/yr5 years

See year-by-year chart →

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

Algal growthTurbidity

Designated uses not supporting: Recreation.

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 Site
Des Moines · 0.7 mi away · NPDES IA0069671
Recent violation
Iowa Methodist Medical Center
Des Moines · 1.3 mi away · NPDES IA0052446
Recent violation
Bituminous Materials And Supply, Lp
Des Moines · 2.2 mi away · NPDES IA0073172
Recent violation
Mercyone Des Moines Medical Center
Des Moines · 2.2 mi away · NPDES IA0081477
Recent violation
Iowa Lutheran Hospital
Des Moines · 2.7 mi away · NPDES IA0052438
Recent violation
Archer Daniels Midland Company
Des Moines · 4.9 mi away · NPDES IA0072958
Recent 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.

Nearby Lakes in Polk County

Fort des Moines Park Pond2.8 ft clear · Hypereutrophic4 miView →Easter Lake2.9 ft clear · Eutrophic4.6 miView →Blue Heron Lake2.2 ft clear · Hypereutrophic4.8 miView →Terra Park Lake11.5 ft clear · Mesotrophic7.2 miView →Brenton Slough—View →Saylorville Lake—View →

Frequently asked questions about Grays Lake

Where is Grays Lake?: Grays Lake is a lake in Polk County, Iowa. Its water-quality measurements are published by Iowa DNR and shown on this page as reported.
What is the water quality of Grays Lake?: Grays Lake in Polk County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 1.6 ft visibility. Phosphorus: 103 µg/L. Chlorophyll-a (algae): 46.5 µg/L.
Is Grays Lake safe to swim in?: Nutrient and algae readings are 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.
Can I fish at Grays Lake?: Public access to Grays Lake is listed as yes on the lake record. Seasons, size and bag limits, and whether you need a license are set by Iowa's fish and wildlife agency, so check its current regulations before you go.

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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 Data21IOWA_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)

21IOWA_WQX-22770006

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.