Eldred Sherwood Lake is a 23-acre productive, nutrient-rich eutrophic lake in Hancock County, Iowa. Water quality is graded F based on 2 sampling years through 2024. Overall water quality is improving over recent sampling years. Compared to the 1 other monitored lakes in Hancock County, Eldred Sherwood Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-10-28. Grade methodology: LakeGrade methodology.
Watch Eldred Sherwood Lake water quality
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Swimming Safety
Based on E. coli testing, Eldred Sherwood Lake never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 28 samples across 2 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: F, Very Poor
Very murky, less than 3 ft of visibility. Chlorophyll-a: 33.4 µg/L. Trophic State Index: 63.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 33.4 µg/L | F |
| Trophic State Index (TSI) | 63 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 23 acres |
Where to stay near Eldred Sherwood Lake
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Fishing Eldred Sherwood Lake
Water Quality Trend: ↑ Improving
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.153 m/yr | 4 |
| Chlorophyll-a | ↑ Improving | -6.37 µg/L/yr | 4 |
Water Temperature
Eldred Sherwood Lake averages about 72°F at the surface in summer, usually warmest in Jul (about 76°F) and coldest in May (about 60°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 35 field readings (2010–2023) via the EPA Water Quality Portal. See the full Eldred Sherwood Lake water temperature breakdown →
Location & Depth Map
Free interactive depth-contour map of Eldred Sherwood Lake, reaching a maximum surveyed depth of 21 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
County Ranking
Ranked #2 of 2 lakes in Hancock County
Cleaner Lakes Within 30 Miles
Eldred Sherwood Lake holds Grade F. 4 nearby lakes hold higher grades.
- ABlue Pit LakeCerro Gordo County · 22.2 mi · Two grade letters higher (F → A)
- DLake CorneliaWright County · 12.2 mi · Higher grade (F → D)
- DClear LakeCerro Gordo County · 14.8 mi · Higher grade (F → D)
- DBlack Pit LakeCerro Gordo County · 22 mi · Higher grade (F → D)
Nearby Lakes in Hancock County
Explore Eldred Sherwood Lake 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)
Eldred Sherwood Lake is a man-made reservoir impounded by the Eldred Sherwood Park Lake Dam (completed 1967), built primarily for other on the TR-EAST BRANCH IOWA RIVER; earth-type dam, 33 ft tall and 555 ft long.
- Surface area
- 23 ac
- Normal storage
- 220 ac-ft
- Max storage
- 360 ac-ft
- Drainage area
- 4.45 sq mi
- Hazard class
- Low
- Owner
- Hancock County Conservation Board
Source: USACE National Inventory of Dams, NID ID IA00438 · Operator website · Matched by proximity (0.05 km)
EPA Impairment Status
Eldred Sherwood Lake 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 02-IOW-773 · Official waterbody report
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 Eldred Sherwood Lake under Clean Water Act (NPDES) discharge permits. 2 facilities have a reported Clean Water Act violation in the past three years.
- Goodell City Of StpGoodell · 2.5 mi away · NPDES IA0082562Recent violation
- Klemme City Of StpKlemme · 4.7 mi away · NPDES IA0038466Recent 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)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2024-10-28
Monitoring stations: 1