Humeston Reservoir
Wayne County, Iowa37 acresView mapDirections
Nutrients and algae run well above the regional average.
- Hypereutrophic
- #3 of 3 in the county
- 33 ft max depth
Humeston Reservoir in Wayne County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 1.6 ft visibility. Phosphorus: 181 µg/L. Chlorophyll-a (algae): 41.4 µg/L. Surface area: 37.4 acres.
- Clarity
- 1.6 ft
- Max depth
- ~33 ft est.
- Area
- 37 acres
- Type
- Hypereutrophic
- Phosphorus
- 181 µg/L
- Chlorophyll-a
- 41.4 µg/L
- Trend
- ↓ Declining
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Stays near Humeston Reservoir
Compare lakeside cabins, hotels, and vacation rentals near Humeston Reservoir in Wayne 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 Humeston Reservoir are listed below.
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Watch Humeston Reservoir’s letter
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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.
Humeston Reservoir is a 37-acre highly nutrient-loaded hypereutrophic lake in Wayne County, Iowa with an estimated average depth of about 33 feet. 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: 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. Check local advisories before you swim.
Water Quality Grade: F (Algae-prone)
Very murky, less than 1.6 ft of visibility. Phosphorus 181 µg/L. Chlorophyll-a 41.4 µg/L. TSI 72. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.6 ft | Not graded |
| Phosphorus | 181 µg/L | Poor |
| Chlorophyll-a (Algae) | 41.4 µg/L | Poor |
| Trophic State Index (TSI) | 72 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~33 ft est. |
| Average Depth | ~7 ft est. |
| Surface Area | 37 acres |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Iowa has not published bathymetry for Humeston Reservoir.
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.
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 |
| Phosphorus | ↓ Declining | +118 µg/L/yr | 2 |
| Chlorophyll-a | ↓ Declining | +32.5 µg/L/yr | 2 |
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
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.
County Ranking
Ranked #3 of 3 lakes in Wayne County
Nearby Lakes With Higher Grades
Humeston Reservoir holds Grade F. One nearby lake has a higher nutrient-and-algae grade — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Wayne County
Frequently asked questions about Humeston Reservoir
Where is Humeston Reservoir?
- Humeston Reservoir is a lake in Wayne County, Iowa. LakeQuality grades it F for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Humeston Reservoir?
- Humeston Reservoir in Wayne County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 1.6 ft visibility. Phosphorus: 181 µg/L. Chlorophyll-a (algae): 41.4 µg/L. Surface area: 37.4 acres.
Is Humeston Reservoir safe to swim in?
- The F is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
How deep is Humeston Reservoir?
- No published bathymetric survey covers Humeston Reservoir, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 33 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate. The lake covers 37.4 acres.
Explore Humeston Reservoir across LakeQuality
More Iowa Lake Rankings
Other Grade F Lakes in Iowa
Hypereutrophic Lakes in Iowa
Where this data comes from
35 measurements from 1 monitoring station, 2023–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Iowa DNR Surface Water Monitoring Data
21IOWA_WQX35 samples · 2023–2024
Analytical methods
- Unknown
- Phosphorus by Colorimetry
- 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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)