Green Belt Lake is a productive, nutrient-rich eutrophic lake in Black Hawk County, Iowa. Water quality is graded D based on 2 sampling years through 2024. Water clarity is improving over recent sampling years. Compared to the 6 other monitored lakes in Black Hawk County, Green Belt Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-10-28. Grade methodology: LakeGrade methodology.
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Swimming Safety
Swimming not recommended, poor water quality with high algae risk
Water Quality Grade: D, Poor
Very murky, less than 2.4 ft of visibility. Chlorophyll-a: 21.2 µg/L. Trophic State Index: 63.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.4 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 21.2 µg/L | D |
| Trophic State Index (TSI) | 63 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Green Belt Lake
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Fishing Green Belt Lake
Water Quality Trend: → Stable
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.022 m/yr | 4 |
| Chlorophyll-a | ↓ Declining | +4.3 µg/L/yr | 4 |
Water Temperature
Green Belt Lake averages about 79°F at the surface in summer, usually warmest in Jul (about 81°F) and coldest in Sep (about 75°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 32 field readings (2010–2023) via the EPA Water Quality Portal. See the full Green Belt Lake water temperature breakdown →
Location & Depth Map
Free interactive depth-contour map of Green Belt Lake, reaching a maximum surveyed depth of 18 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
County Ranking
Ranked #2 of 7 lakes in Black Hawk County
Cleaner Lakes Within 30 Miles
Green Belt Lake holds Grade D. One nearby lake has a higher grade.
See full comparison →Nearby Lakes in Black Hawk County
Explore Green Belt Lake across LakeGrade
More Iowa Lake Rankings
Other Grade D Lakes in Iowa
Eutrophic Lakes in Iowa
More records, surveys & data sources
Regulated Pollution Sources Nearby
4 EPA-permitted facilities operate within about 5 miles of Green Belt Lake under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger. 1 facility has a reported Clean Water Act violation in the past three years.
- John Deere Waterloo Works (Drive Train Operations)Waterloo · 2.5 mi away · NPDES IA0000060Major
- John Deere Product Engineering CenterCedar Falls · 1.4 mi away · NPDES IA0062481Recent violation
- John Deere Foundry WaterlooWaterloo · 2.3 mi away · NPDES IA0069485
- Magellan Pipeline Company, L.P.Waterloo · 3.3 mi away · NPDES IA0072672
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2024-10-28
Monitoring stations: 1