Windmill Lake
Taylor County, Iowa25 acresView mapDirections
Iowa DNR publishes the water-quality measurements for Windmill Lake. Here is what has been measured.
- Hypereutrophic
- Impaired · Turbidity
Windmill Lake in Taylor County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 2.5 ft visibility. Phosphorus: 94 µg/L. Chlorophyll-a (algae): 33.9 µg/L. Surface area: 24.5 acres.
Free interactive depth-contour map of Windmill Lake, reaching a maximum surveyed depth of 16 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
Windmill Lake is a 25-acre highly nutrient-loaded hypereutrophic lake in Taylor County, Iowa. Overall water quality is declining over recent sampling years. Compared to the 3 other monitored lakes in Taylor County, Windmill Lake ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-10-01. Methodology: how these readings are compared.
Swimming conditions
Readings onlyRecreation 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. Windmill Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for turbidity. Check local advisories before you swim.
Whether Windmill 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 Windmill Lake
These are the measurements Iowa DNR publishes for Windmill 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 2.5 ft of visibility. Phosphorus 94 µg/L. Chlorophyll-a 33.9 µg/L. TSI 66.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 94µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 33.9µg/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. | 66 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Windmill Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Windmill Lake typically sits around 73°F at the surface in September. Summer average is about 80°F. Usually warmest in Jul (about 83°F) and coldest in Sep (about 73°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (73°F) to its warmest (83°F).
Typical surface water temperature by month, from 31 field readings (2010–2023) via the EPA Water Quality Portal. See the full Windmill Lake water temperature breakdown →
Lake Details
Surface area
25 acres
No bathymetric survey has been published for Windmill Lake, so its depth is not documented here.
Stays via Stay22
Stays near Windmill Lake
Compare lakeside cabins, hotels, and vacation rentals near Windmill Lake in Taylor 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 Windmill Lake are listed below.
Top-rated places to stay near Windmill Lake
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Fishing Windmill Lake
Water Quality Trend: Worsening
Based on 4 years of monitoring (2021–2024).
Water clarity
Worsening4 years
Phosphorus
Worsening+10 µg/L/yr4 years
Chlorophyll-a
Worsening+15.62 µg/L/yr4 years
Reservoir Info (USACE NID)
Windmill Lake is a man-made reservoir impounded by the Windmill Lake Dam (completed 1969), built primarily for recreation on the TR-WEST BRANCH 102 RIVER; earth-type dam, 35 ft tall and 900 ft long.
- Surface area
- 24.5 ac
- Normal storage
- 66 ac-ft
- Max storage
- 247 ac-ft
- Drainage area
- 0.84 sq mi
- Hazard class
- Low
- Owner
- Taylor County Conservation Board
Source: USACE National Inventory of Dams, NID ID IA01053 · Operator website
EPA Impairment Status
Windmill Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IA 05-PLA-1482 · Official waterbody report
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Windmill Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- New Market City Of StpNew Market · 3.3 mi away · NPDES IA0033049Recent violation
- Gravity, City Of (Southern Iowa Rural Water Assn.)Gravity · 3.5 mi away · NPDES IA0075957
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 Taylor County
Frequently asked questions about Windmill Lake
Where is Windmill Lake?
- Windmill Lake is a lake in Taylor County, Iowa. Its water-quality measurements are published by Iowa DNR and shown on this page as reported.
What is the water quality of Windmill Lake?
- Windmill Lake in Taylor County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 2.5 ft visibility. Phosphorus: 94 µg/L. Chlorophyll-a (algae): 33.9 µg/L. Surface area: 24.5 acres.
Is Windmill Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Windmill Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for turbidity. Check local advisories before you swim.
What is the water temperature of Windmill Lake?
- Windmill Lake typically sits around 73°F at the surface in September, from 31 EPA Water Quality Portal field readings (2010–2023). That is a typical value for the month, not a live reading.
Explore Windmill Lake across LakeQuality
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Where this data comes from
48 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_WQX48 samples · 2021–2024
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)
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)