Oldham Lake
Monona County, Iowa16 acresView mapDirections
Iowa DNR publishes the water-quality measurements for Oldham Lake. Here is what has been measured.
- Eutrophic
Oldham Lake in Monona County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 5.1 ft visibility. Phosphorus: 46 µg/L. Chlorophyll-a (algae): 8.5 µg/L. Surface area: 16.1 acres.
Free interactive depth-contour map of Oldham Lake, reaching a maximum surveyed depth of 18 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
Oldham Lake is a 16-acre productive, nutrient-rich eutrophic lake in Monona County, Iowa. Overall water quality is declining over recent sampling years. Compared to the 1 other monitored lakes in Monona County, Oldham Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-09-03. 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 Oldham 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 Oldham Lake
These are the measurements Iowa DNR publishes for Oldham Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Murky, only visible to about 5.1 ft. Phosphorus 46 µg/L. Chlorophyll-a 8.5 µg/L. TSI 55.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 5.1ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 46µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | 8.5µg/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. | 55 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Oldham Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Oldham Lake typically sits around 77°F at the surface in August. Summer average is about 77°F. Usually warmest in Jun (about 77°F) and coldest in May (about 64°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (64°F) to its warmest (77°F).
Typical surface water temperature by month, from 26 field readings (2010–2023) via the EPA Water Quality Portal. See the full Oldham Lake water temperature breakdown →
Lake Details
Surface area
16 acres
No bathymetric survey has been published for Oldham Lake, so its depth is not documented here.
Stays via Stay22
Stays near Oldham Lake
Compare lakeside cabins, hotels, and vacation rentals near Oldham Lake in Monona 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.
Top-rated places to stay near Oldham 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.
Planning a whole trip? See where to stay at Iowa’s top lakes →
Follow Oldham Lake’s readings
Email me when new measurements post for this lake. Updates stay free.
Or email
Fishing Oldham Lake
Water Quality Trend: Worsening
Based on 4 years of monitoring (2021–2024).
Water clarity
Worsening4 years
Phosphorus
Worsening+1.35 µg/L/yr4 years
Chlorophyll-a
Stable+0.15 µg/L/yr4 years
Reservoir Info (USACE NID)
Oldham Lake is a man-made reservoir impounded by the Davis-Battle Cr. Watershed Site D-3 (completed 1963), built primarily for fire protection, stock, or small fish pond on the TR-SOLDIER RIVER; earth-type dam, 46 ft tall and 600 ft long.
- Surface area
- 16.1 ac
- Normal storage
- 194 ac-ft
- Max storage
- 285 ac-ft
- Drainage area
- 1.06 sq mi
- Hazard class
- Low
- Owner
- Monona County SWCD
All listed purposes: Fire Protection, Stock, Or Small Fish Pond;Flood Risk Reduction.
Source: USACE National Inventory of Dams, NID ID IA00771 · Operator website · Matched by proximity (0.08 km)
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Oldham Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Ute City Of StpUte · 4.7 mi away · NPDES IA0043010Recent violation
- Soldier City Of StpSoldier · 1.9 mi away · NPDES IA0061743
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 Monona County
Frequently asked questions about Oldham Lake
Where is Oldham Lake?
- Oldham Lake is a lake in Monona County, Iowa. Its water-quality measurements are published by Iowa DNR and shown on this page as reported.
What is the water quality of Oldham Lake?
- Oldham Lake in Monona County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 5.1 ft visibility. Phosphorus: 46 µg/L. Chlorophyll-a (algae): 8.5 µg/L. Surface area: 16.1 acres.
Is Oldham Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Oldham Lake?
- Oldham Lake typically sits around 77°F at the surface in August, from 26 EPA Water Quality Portal field readings (2010–2023). That is a typical value for the month, not a live reading.
Explore Oldham Lake across LakeQuality
More lakes in Iowa
Other Lakes in Iowa
Eutrophic Lakes in Iowa
Where this data comes from
54 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_WQX54 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
Regulated discharger data from EPA ECHO (ICIS-NPDES)