Lake Iowa is a 92-acre productive, nutrient-rich eutrophic lake in Iowa County, Iowa. Water quality is graded F based on 2 sampling years through 2024. Water clarity is improving over recent sampling years. Limited fish-species data available. Public access is available. Compared to the 6 other monitored lakes in Iowa County, Lake Iowa ranks #5 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-10-01. Grade methodology: LakeGrade methodology.
Watch Lake Iowa water quality
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Swimming Safety
Based on E. coli testing, Lake Iowa never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 17 samples across 6 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 1.9 ft of visibility. Chlorophyll-a: 53.8 µg/L. Trophic State Index: 69.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.9 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 53.8 µg/L | F |
| Trophic State Index (TSI) | 69 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 92 acres |
| Public Access | Yes |
Where to stay near Lake Iowa
Compare lakeside cabins, hotels, and vacation rentals near Lake Iowa in Iowa 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 Iowa
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Fishing Lake Iowa
Water Quality Trend: → Stable
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.097 m/yr | 5 |
| Chlorophyll-a | ↓ Declining | +3.42 µg/L/yr | 5 |
Water Temperature
Lake Iowa averages about 78°F at the surface in summer, usually warmest in Jul (about 80°F) and coldest in Sep (about 69°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 38 field readings (2010–2023) via the EPA Water Quality Portal. See the full Lake Iowa water temperature breakdown →
Location & Depth Map
Free interactive depth-contour map of Lake Iowa, reaching a maximum surveyed depth of 28 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
County Ranking
Ranked #5 of 7 lakes in Iowa County
Cleaner Lakes Within 30 Miles
Lake Iowa holds Grade F. One nearby lake has a higher grade.
See full comparison →Nearby Lakes in Iowa County
Explore Lake Iowa 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)
Lake Iowa is a man-made reservoir impounded by the Lake Iowa Dam (completed 1962), built primarily for recreation on the PIG CREEK; earth-type dam, 40 ft tall and 893 ft long.
- Surface area
- 92 ac
- Normal storage
- 1,110 ac-ft
- Max storage
- 1,950 ac-ft
- Drainage area
- 2.17 sq mi
- Hazard class
- Significant
- Owner
- Iowa County Conservation Board
Source: USACE National Inventory of Dams, NID ID IA00520 · Operator website
EPA Impairment Status
Lake Iowa 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-677 · Official waterbody report
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Lake Iowa under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- East Iowa Bible Camp-StpDeep River · 4.4 mi away · NPDES IA0075213Recent 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: 2024-10-01
Monitoring stations: 1