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. Limited fish-species data available. Public access is available with 1 public boat landing. 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: LakeGrade methodology.
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Swimming Safety
Avoid swimming, very poor water quality, potential algae toxins
Water Quality Grade: F, Very Poor
Very murky, less than 1.4 ft of visibility. Chlorophyll-a: 68.7 µg/L. Trophic State Index: 72.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.4 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 68.7 µg/L | F |
| Trophic State Index (TSI) | 72 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 20 acres |
| Public Access | Yes |
Where to stay near White Oak Lake
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Fishing White Oak Lake
Water Quality Trend: → Stable
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.007 m/yr | 5 |
| Chlorophyll-a | → Stable | -0.17 µg/L/yr | 5 |
Recreation & Access
Water Temperature
White Oak Lake averages about 78°F at the surface in summer, 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 →
Location & Depth Map
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.
County Ranking
Ranked #2 of 3 lakes in Mahaska County
Cleaner Lakes Within 30 Miles
White Oak Lake holds Grade F. 2 nearby lakes hold higher grades.
- BYenruogis PondKeokuk County · 16 mi · Two grade letters higher (F → B)
- DHawthorn LakeMahaska County · 14 mi · Higher grade (F → D)
Nearby Lakes in Mahaska County
Explore White Oak Lake across LakeGrade
More Iowa Lake Rankings
Other Grade F Lakes in Iowa
Hypereutrophic Lakes in Iowa
More records, surveys & data sources
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.
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Grading methodology based on Metropolitan Council standards
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2024-08-28
Monitoring stations: 1