Lake County, Illinois · Water Quality Report Card
Deep Lake
Deep Lake in Lake County, Illinois has a water quality grade of A (Excellent). Chlorophyll-a (algae): 2.2 µg/L.
- Mean depth
- ~13 ft est.
- Type
- Mesotrophic
Deep Lake is a mesotrophic lake in Lake County, Illinois with an estimated average depth of about 13 feet. Water quality is graded A based on 1 sampling years through 2022. Compared to the 18 other monitored lakes in Lake County, Deep Lake ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2022-08-10. Grade methodology: LakeGrade methodology.
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Swimming Safety
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A (Excellent)
No clarity data. Chlorophyll-a: 2.2 µg/L. Trophic State Index: 38.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No data | |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 2.2 µg/L | Good |
| Trophic State Index (TSI) | 38 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Average Depth | ~13 ft est. |
Depth marked “est.” is a modeled estimate from HydroLAKES, not a measured survey. Illinois has not published bathymetry for Deep Lake.
Where to stay near Deep Lake
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Fishing Deep Lake
Location
County Ranking
Ranked #4 of 19 lakes in Lake County
Nearby Lakes in Lake County
Explore Deep Lake across LakeGrade
Species activity outlook by water temperature and season
Top lakes and where to stay in the Chain O'Lakes area
Where to stay at Illinois's top lakes, each with its grade
Moderate nutrients, good water quality
Illinois's cleanest and most-polluted lakes, ranked
More Illinois Lake Rankings
Other Grade A Lakes in Illinois
Mesotrophic Lakes in Illinois
More records, surveys & data sources
EPA Impairment Status
Deep Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IL_VTD · Official waterbody report
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Where this data comes from
8 measurements from 1 monitoring station, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- illinois epa
IL_EPA_WQX8 samples · 2022
Analytical methods
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
Monitoring station identifiers (1)
Grade thresholds come from the U.S. EPA National Lakes Assessment 2022 Technical Support Document (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated.
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion
Most recent sample: 2022-08-10
Monitoring stations: 1