Humeston Reservoir is a 37-acre productive, nutrient-rich eutrophic lake in Wayne County, Iowa. Water quality is graded F based on 2 sampling years through 2024. Overall water quality is declining over recent sampling years. Compared to the 2 other monitored lakes in Wayne County, Humeston Reservoir ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-09-09. 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 1.6 ft of visibility. Chlorophyll-a: 41.4 µg/L. Trophic State Index: 69.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.6 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 41.4 µg/L | F |
| Trophic State Index (TSI) | 69 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 37 acres |
Where to stay near Humeston Reservoir
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Fishing Humeston Reservoir
Water Quality Trend: ↓ Declining
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.34 m/yr | 2 |
| Chlorophyll-a | ↓ Declining | +32.5 µg/L/yr | 2 |
Location & Depth Map
Free interactive depth-contour map of Humeston Reservoir, 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 #3 of 3 lakes in Wayne County
Cleaner Lakes Within 30 Miles
Humeston Reservoir holds Grade F. 2 nearby lakes hold higher grades.
- DBob White LakeWayne County · 12.6 mi · Higher grade (F → D)
- DWest Lake OsceolaClarke County · 19 mi · Higher grade (F → D)
Nearby Lakes in Wayne County
Explore Humeston Reservoir across LakeGrade
More Iowa Lake Rankings
Other Grade F Lakes in Iowa
Eutrophic Lakes in Iowa
More records, surveys & data sources
Reservoir Info (USACE NID)
Humeston Reservoir is a man-made reservoir impounded by the Humeston Reservoir Dam (completed 1916), built primarily for water supply on the TR-CHARITON RIVER; earth-type dam, 31 ft tall and 670 ft long.
- Surface area
- 37.4 ac
- Normal storage
- 340 ac-ft
- Max storage
- 900 ac-ft
- Drainage area
- 1.02 sq mi
- Hazard class
- Significant
- Owner
- City of Humeston
All listed purposes: Water Supply;Recreation.
Source: USACE National Inventory of Dams, NID ID IA01383 · Operator website
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Humeston Reservoir under Clean Water Act (NPDES) discharge permits. 2 facilities have a reported Clean Water Act violation in the past three years.
- Humeston City Of StpHumeston · 0.9 mi away · NPDES IA0043150Recent violation
- Derby City Of StpDerby · 4.6 mi away · NPDES IA0080322Recent 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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2024-09-09
Monitoring stations: 1