Big Crooked Lake South Basin; Grattan Township is a mesotrophic lake in Kent County, Michigan. Water quality is graded B based on 1 sampling years through 2021. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available. Compared to the 17 other monitored lakes in Kent County, Big Crooked Lake South Basin; Grattan Township ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, Michigan DNR, last sampled 2021-09-18. Grade methodology: LakeGrade methodology.
Watch Big Crooked Lake South Basin; Grattan Township water quality
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Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
Good clarity, visible to about 11.5 ft. Trophic State Index: 42.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 11.5 ft | B |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 42 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Big Crooked Lake South Basin; Grattan Township
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Fishing Big Crooked Lake South Basin; Grattan Township
Water Quality Trend: ↓ Declining
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -2.33 m/yr | 2 |
Location
County Ranking
Ranked #4 of 18 lakes in Kent County
Nearby Lakes in Kent County
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Moderate nutrients, good water quality
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More records, surveys & data sources
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 Big Crooked Lake South Basin; Grattan Township under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Carmelite MonasteryAda · 1.3 mi away · NPDES MIG250375Recent 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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2021-09-18
Monitoring stations: 1