Mahaska County, Iowa · Water Quality Report Card
Lake Keomah Beach
Lake Keomah Beach in Mahaska County, Iowa is not rated for water quality — its monitoring record does not meet the evidence bar.
- Mean depth
- ~15 ft est.
- Trend
- ↑ Improving
Lake Keomah Beach is a lake in Mahaska County, Iowa with an estimated average depth of about 15 feet. Overall water quality is improving over recent sampling years.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-05-29. Grade methodology: LakeGrade methodology.
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Swimming Safety
Based on E. coli testing, Lake Keomah Beach routinely exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 25% of 100 samples across 7 seasons.
This is a historical summary of past testing, not a current condition — bacteria levels change quickly, especially after rain. Always check Iowa’s current beach and health-department advisories before swimming.
Water Quality Grade: Not rated
No clarity data.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No data | |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data |
Lake Details
| Characteristic | Value |
|---|---|
| Average Depth | ~15 ft est. |
Depth marked “est.” is a modeled estimate from HydroLAKES, not a measured survey. Iowa has not published bathymetry for Lake Keomah Beach.
Where to stay near Lake Keomah Beach
Compare lakeside cabins, hotels, and vacation rentals near Lake Keomah Beach 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.
Top-rated places to stay near Lake Keomah Beach
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Fishing Lake Keomah Beach
Water Quality Trend: ↑ Improving
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.006 m/yr | 4 |
| Phosphorus | ↑ Improving | -28 µg/L/yr | 3 |
| Chlorophyll-a | ↑ Improving | -3.56 µg/L/yr | 4 |
Location
Nearby Lakes in Mahaska County
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More records, surveys & data sources
EPA Impairment Status
Lake Keomah Beach is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IA 03-SSK-930 · Official waterbody report · Matched by proximity (0.24 km)
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Where this data comes from
28 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_WQX28 samples · 2021–2024
Analytical methods
- 2130 B ~ Nephelometric Method
Monitoring station identifiers (1)
Grade thresholds come from the U.S. EPA National Lakes Assessment 2022 Technical Support Document (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated.
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion
Most recent sample: 2024-05-29
Monitoring stations: 1