Little Wall Lake is a highly nutrient-loaded hypereutrophic lake in Hamilton County, Iowa. Water quality is graded F based on 2 sampling years through 2024. Water clarity is improving over recent sampling years. Compared to the 1 other monitored lakes in Hamilton County, Little Wall Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-10-30. Grade methodology: LakeGrade methodology.
Watch Little Wall Lake water quality
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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 0.7 ft of visibility. Chlorophyll-a: 76.6 µg/L. Trophic State Index: 78.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 0.7 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 76.6 µg/L | F |
| Trophic State Index (TSI) | 78 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Where to stay near Little Wall Lake
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Fishing Little Wall Lake
Water Quality Trend: → Stable
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.025 m/yr | 5 |
| Chlorophyll-a | ↓ Declining | +9.76 µg/L/yr | 5 |
Water Temperature
Little Wall Lake averages about 77°F at the surface in summer, usually warmest in Jul (about 82°F) and coldest in May (about 59°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 Little Wall Lake water temperature breakdown →
Location & Depth Map
Free interactive depth-contour map of Little Wall Lake, reaching a maximum surveyed depth of 12 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
County Ranking
Ranked #2 of 2 lakes in Hamilton County
Cleaner Lakes Within 30 Miles
Little Wall Lake holds Grade F. 2 nearby lakes hold higher grades.
- BAda Hayden Heritage Park LakeStory County · 13.9 mi · Two grade letters higher (F → B)
- DHickory Grove LakeStory County · 23.8 mi · Higher grade (F → D)
Nearby Lakes in Hamilton County
Explore Little Wall Lake across LakeGrade
More Iowa Lake Rankings
Other Grade F Lakes in Iowa
Hypereutrophic Lakes in Iowa
More records, surveys & data sources
EPA Impairment Status
Little Wall Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IA 03-SSK-941 · Official waterbody report
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
4 EPA-permitted facilities operate within about 5 miles of Little Wall Lake under Clean Water Act (NPDES) discharge permits. 4 facilities have a reported Clean Water Act violation in the past three years.
- Jewell City Of StpJewell · 2.4 mi away · NPDES IA0024422Recent violation
- Ellsworth City Of StpEllsworth · 3.5 mi away · NPDES IA0026280Recent violation
- Poet Biorefining - JewellJewell · 4.3 mi away · NPDES IA0079588Recent violation
- Ag Partners, LlcEllsworth · 4.8 mi away · NPDES IA0053034Recent 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: 2024-10-30
Monitoring stations: 1