Diamond Lake
Cass County, Michigan1,040 acresView mapDirections
EGLE publishes the water-quality measurements for Diamond Lake. Here is what has been measured.
- Oligotrophic
- 64 ft max depth
- Limited data
Diamond Lake in Cass County, Michigan has water-quality measurements published by EGLE, shown here as reported. Water clarity: 12.3 ft visibility. Phosphorus: 6 µg/L. Chlorophyll-a (algae): 2 µg/L. Maximum depth: 64 ft. Surface area: 1039.8 acres.
Diamond Lake is a 1,040-acre cold, clear oligotrophic lake in Cass County, Michigan with a maximum depth of 64 feet. Overall water quality is declining over recent sampling years. Compared to the 9 other monitored lakes in Cass County, Diamond Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, EGLE, last sampled 2019-09-19. Methodology: how these readings are compared.
What Diamond Lake is good for
From access and monitoring records, not editorial picks.
- Clear water12.3 ft of visibility
- Deep water64 ft surveyed max depth
- Big water1,040 acres
Swimming conditions
Readings onlyLimited data
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Diamond Lake is safe to swim in today is a call for the Michigan Department of Environment, Great Lakes, and Energy (EGLE) and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Diamond Lake
These are the measurements EGLE publishes for Diamond Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Good clarity, visible to about 12.3 ft. Phosphorus 6 µg/L. Chlorophyll-a 2 µg/L. TSI 36.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 12.3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 6µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 2µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 36 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Diamond Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
64 ft
Surface area
1,040 acres
Stays via Stay22
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Fishing Diamond Lake
Water Quality Trend: Worsening
Based on 4 years of monitoring (2016–2019).
Water clarity
Stable4 years
Phosphorus
Worsening+1.2 µg/L/yr4 years
Chlorophyll-a
Worsening+0.39 µg/L/yr4 years
Nearby Lakes in Cass County
Frequently asked questions about Diamond Lake
Where is Diamond Lake?
- Diamond Lake is a lake in Cass County, Michigan. Its water-quality measurements are published by EGLE and shown on this page as reported.
What is the water quality of Diamond Lake?
- Diamond Lake in Cass County, Michigan has water-quality measurements published by EGLE, shown here as reported. Water clarity: 12.3 ft visibility. Phosphorus: 6 µg/L. Chlorophyll-a (algae): 2 µg/L. Maximum depth: 64 ft. Surface area: 1039.8 acres.
Is Diamond Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
How deep is Diamond Lake?
- Diamond Lake has a maximum depth of 64 feet. The lake covers 1039.8 acres.
Explore Diamond Lake across LakeQuality
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Where this data comes from
99 measurements from 1 monitoring station, 2016–2019. Retrieved from the EPA Water Quality Portal on 2026-08-26.
Collected and reported by
- Michigan EGLE - MiCorps
21MICH_MICORPS99 samples · 2016–2019
Analytical methods
- Phosphorus by Colorimetry
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
Monitoring station identifiers (1)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.