Thomas Mitchell Lake
Polk County, Iowa4 acresView mapDirections
Iowa DNR publishes the water-quality measurements for Thomas Mitchell Lake. Here is what has been measured.
- Eutrophic
Thomas Mitchell Lake in Polk County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 3.3 ft visibility. Phosphorus: 87 µg/L. Chlorophyll-a (algae): 13.2 µg/L. Surface area: 4.2 acres.
Free interactive depth-contour map of Thomas Mitchell Lake, reaching a maximum surveyed depth of 18 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
Thomas Mitchell Lake is a 4-acre productive, nutrient-rich eutrophic lake in Polk County, Iowa. Overall water quality is declining over recent sampling years. Compared to the 11 other monitored lakes in Polk County, Thomas Mitchell Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-09-09. Methodology: how these readings are compared.
Swimming conditions
Readings onlyModerate algae
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. Check local advisories before you swim.
Whether Thomas Mitchell 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 Thomas Mitchell Lake
These are the measurements Iowa DNR publishes for Thomas Mitchell 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 3.3 ft of visibility. Phosphorus 87 µg/L. Chlorophyll-a 13.2 µg/L. TSI 61.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 3.3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 87µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 13.2µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 61 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
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Lake Details
Surface area
4 acres
No bathymetric survey has been published for Thomas Mitchell Lake, so its depth is not documented here.
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Fishing Thomas Mitchell Lake
Water quality readings over time
2 seasons of samples on record (2023–2024). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Worsening2 years
Phosphorus
Worsening+27 µg/L/yr2 years
Chlorophyll-a
Improving-11.5 µg/L/yr2 years
Reservoir Info (USACE NID)
Thomas Mitchell Lake is a man-made reservoir impounded by the Thomas Mitchell Park Dam (completed 1971), built primarily for recreation on the TR-CAMP CREEK; earth-type dam, 27 ft tall and 711 ft long.
- Surface area
- 4.2 ac
- Normal storage
- 25 ac-ft
- Max storage
- 75 ac-ft
- Drainage area
- 0.47 sq mi
- Hazard class
- Significant
- Owner
- Polk County Conservation Board
Source: USACE National Inventory of Dams, NID ID IA00901 · Operator website · Matched by proximity (0.24 km)
Regulated Pollution Sources Nearby
3 EPA-permitted facilities operate within about 5 miles of Thomas Mitchell Lake under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger. 2 facilities have a reported Clean Water Act violation in the past three years.
- Mitchellville City Of StpMitchellville · 2 mi away · NPDES IA0021997MajorRecent violation
- Thomas Mitchell ParkMitchellville · 0.3 mi away · NPDES IA0066966Recent violation
- Altoona, City Of MS4Altoona · 4 mi away · NPDES IA0078603
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
Frequently asked questions about Thomas Mitchell Lake
Where is Thomas Mitchell Lake?
- Thomas Mitchell 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 Thomas Mitchell Lake?
- Thomas Mitchell Lake in Polk County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 3.3 ft visibility. Phosphorus: 87 µg/L. Chlorophyll-a (algae): 13.2 µg/L. Surface area: 4.2 acres.
Is Thomas Mitchell Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Explore Thomas Mitchell Lake across LakeQuality
More lakes in Iowa
Other Lakes in Iowa
Eutrophic Lakes in Iowa
Where this data comes from
32 measurements from 1 monitoring station, 2023–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Iowa DNR Surface Water Monitoring Data
21IOWA_WQX32 samples · 2023–2024
Analytical methods
- Unknown
- Phosphorus by Colorimetry
- 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
Regulated discharger data from EPA ECHO (ICIS-NPDES)