Lake Manawa is a highly nutrient-loaded hypereutrophic lake in Pottawattamie 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 with 7 public boat landings. Compared to the 1 other monitored lakes in Pottawattamie County, Lake Manawa ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-09-30. Grade methodology: LakeGrade methodology.
Watch Lake Manawa water quality
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Swimming Safety
Based on E. coli testing, Lake Manawa frequently exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 17.4% of 109 samples across 7 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 ft of visibility. Chlorophyll-a: 77 µg/L. Trophic State Index: 75.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 77 µg/L | F |
| Trophic State Index (TSI) | 75 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Where to stay near Lake Manawa
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Fishing Lake Manawa
Water Quality Trend: → Stable
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.033 m/yr | 4 |
| Chlorophyll-a | ↓ Declining | +30.01 µg/L/yr | 4 |
Recreation & Access
Water Temperature
Lake Manawa averages about 81°F at the surface in summer, usually warmest in Jul (about 84°F) and coldest in May (about 71°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 105 field readings (2010–2023) via the EPA Water Quality Portal. See the full Lake Manawa water temperature breakdown →
Location & Depth Map
Free interactive depth-contour map of Lake Manawa, 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 Pottawattamie County
Nearby Lakes in Pottawattamie County
Explore Lake Manawa across LakeGrade
More Iowa Lake Rankings
Other Grade F Lakes in Iowa
Hypereutrophic Lakes in Iowa
More records, surveys & data sources
EPA Impairment Status
Lake Manawa is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit IA 06-WEM-1711 · Official waterbody report
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
10 EPA-permitted facilities operate within about 5 miles of Lake Manawa under Clean Water Act (NPDES) discharge permits, including 2 classified by the EPA as major dischargers. 6 facilities have a reported Clean Water Act violation in the past three years.
- Walter Scott Jr. Energy CenterCouncil Bluffs · 2 mi away · NPDES IA0004308MajorRecent violation
- Council Bluffs City Of StpCouncil Bluffs · 2.7 mi away · NPDES IA0036641MajorRecent violation
- Buckeye Terminals, Llc - Council Bluffs TerminalCouncil Bluffs · 1.5 mi away · NPDES IA0071234Recent violation
- Nustar Council Bluffs TerminalCouncil Bluffs · 1.6 mi away · NPDES IA0046752Recent violation
- Southwest Iowa Renewable EnergyCouncil Bluffs · 2.8 mi away · NPDES IA0081043Recent violation
- Chapters Council Bluffs Opco, Llc (Dba Chapters Living Of Council Bluffs)Council Bluffs · 3.5 mi away · NPDES IA0071269Recent 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
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2024-09-30
Monitoring stations: 1