Riddles Lake
St. Joseph County, Indiana78 acresView mapDirections
IDEM publishes the water-quality measurements for Riddles Lake. Here is what has been measured.
- Impaired · Nutrients (phosphorus, nitrogen)
- 20 ft max depth
- Limited data
Riddles Lake in St. Joseph County, Indiana has water-quality measurements published by IDEM, shown here as reported. Phosphorus: 133.8 µg/L. Chlorophyll-a (algae): 92.3 µg/L. Maximum depth: 20 ft. Surface area: 78 acres.
Riddles Lake is a 78-acre lake in St. Joseph County, Indiana with a maximum depth of 20 feet (8-foot average).
Source: EPA Water Quality Portal sampling records, IDEM, last sampled 2021-07-14. Methodology: how these readings are compared.
Swimming conditions
No readingRecreation use not supported
Nutrient and algae readings are not a swimming clearance. Riddles Lake is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Riddles Lake is safe to swim in today is a call for the Indiana Department of Environmental Management and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Riddles Lake
These are the measurements IDEM publishes for Riddles Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data. Phosphorus 133.8 µg/L. Chlorophyll-a 92.3 µg/L.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | No reading How deep a black-and-white disk stays visible from the surface. Higher is clearer. | |
| Total phosphorus | 134µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | 92.3µg/L | Measured, not scored The green pigment in algae — a direct measure of how much algae is in the water. |
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Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
20 ft
Average depth
7.9 ft
Surface area
78 acres
Shoreline
2 mi
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Fishing Riddles Lake
EPA Impairment Status
Riddles Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Recreation.
Source: EPA ATTAINS assessment unit INK01P1069_00 · Official waterbody report
Nearby Lakes in St. Joseph County
Frequently asked questions about Riddles Lake
Where is Riddles Lake?
- Riddles Lake is a lake in St. Joseph County, Indiana. Its water-quality measurements are published by IDEM and shown on this page as reported.
What is the water quality of Riddles Lake?
- Riddles Lake in St. Joseph County, Indiana has water-quality measurements published by IDEM, shown here as reported. Phosphorus: 133.8 µg/L. Chlorophyll-a (algae): 92.3 µg/L. Maximum depth: 20 ft. Surface area: 78 acres.
Is Riddles Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Riddles Lake is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
How deep is Riddles Lake?
- Riddles Lake has a maximum depth of 20 feet and an average depth of 7.9 feet. The lake covers 78 acres.
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Where this data comes from
Measurements for Riddles Lake come from the EPA Water Quality Portal. Per-sample source details are not recorded for this lake.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database