White Oak Lake
Mahaska County, Iowa20 acresView mapDirections
Nutrients and algae run well above the regional average.
- Hypereutrophic
- Impaired · Algal growth
- #2 of 3 in the county
- Public access
White Oak Lake in Mahaska County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 1.4 ft visibility. Phosphorus: 125.5 µg/L. Chlorophyll-a (algae): 68.7 µg/L. Surface area: 20 acres.
- Clarity
- 1.4 ft
- Typical in September
- 68°F
- Area
- 20 acres
- Type
- Hypereutrophic
- Phosphorus
- 125.5 µg/L
- Chlorophyll-a
- 68.7 µg/L
- Trend
- ↓ Declining
- Public access
- Yes
Stays via Stay22
Stays near White Oak Lake
Compare lakeside cabins, hotels, and vacation rentals near White Oak Lake in Mahaska 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 White Oak Lake are listed below.
Top-rated places to stay near White Oak 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 White Oak Lake’s letter
Email me if this lake’s grade moves. Grades stay free.
Or email
Free interactive depth-contour map of White Oak Lake, reaching a maximum surveyed depth of 16 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
White Oak Lake is a 20-acre highly nutrient-loaded hypereutrophic lake in Mahaska 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 2 other monitored lakes in Mahaska County, White Oak Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-08-28. 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. White Oak 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 1.4 ft of visibility. Phosphorus 125.5 µg/L. Chlorophyll-a 68.7 µg/L. TSI 73. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.4 ft | Not graded |
| Phosphorus | 125.5 µg/L | Poor |
| Chlorophyll-a (Algae) | 68.7 µg/L | Poor |
| Trophic State Index (TSI) | 73 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Water Temperature
White Oak Lake typically sits around 68°F at the surface in September. Summer average is about 78°F. Usually warmest in Aug (about 80°F) and coldest in Sep (about 68°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 29 field readings (2010–2023) via the EPA Water Quality Portal. See the full White Oak Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 20 acres |
| Public Access | Yes |
No bathymetric survey has been published for White Oak Lake, so its depth is not documented here.
Fishing White Oak Lake
Water Quality Trend: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.007 m/yr | 5 |
| Phosphorus | ↓ Declining | +52.3 µg/L/yr | 4 |
| Chlorophyll-a | → Stable | -0.17 µg/L/yr | 5 |
Reservoir Info (USACE NID)
White Oak Lake is a man-made reservoir impounded by the White Oak Lake Dam (completed 1983), built primarily for recreation on the TR- SNYDER CR.; earth-type dam, 39 ft tall and 555 ft long.
- Surface area
- 20 ac
- Normal storage
- 168 ac-ft
- Max storage
- 393 ac-ft
- Drainage area
- 0.94 sq mi
- Hazard class
- Significant
- Owner
- Mahaska County Conservation Board
Source: USACE National Inventory of Dams, NID ID IA02274 · Operator website
EPA Impairment Status
White Oak 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 03-SSK-929 · Official waterbody report · Matched by proximity (0.3 km)
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of White Oak Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Rose Hill City Of StpRose Hill · 2.9 mi away · NPDES IA0072311Recent 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 #2 of 3 lakes in Mahaska County
Nearby Lakes With Higher Grades
White Oak Lake holds Grade F. 2 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 Mahaska County
Frequently asked questions about White Oak Lake
Where is White Oak Lake?
- White Oak Lake is a lake in Mahaska County, Iowa. LakeQuality grades it F for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for White Oak Lake?
- White Oak Lake in Mahaska County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 1.4 ft visibility. Phosphorus: 125.5 µg/L. Chlorophyll-a (algae): 68.7 µg/L. Surface area: 20 acres.
Is White Oak Lake safe to swim in?
- The F is nutrients and algae, not a swimming clearance. White Oak 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 White Oak Lake?
- White Oak Lake typically sits around 68°F at the surface in September, from 29 EPA Water Quality Portal field readings (2010–2023). That is a typical value for the month, not a live reading.
Explore White Oak Lake across LakeQuality
More Iowa Lake Rankings
Other Grade F Lakes in Iowa
Hypereutrophic Lakes in Iowa
Where this data comes from
63 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_WQX63 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)