Catherine Lake
Lake County, IllinoisView mapDirections
Illinois EPA publishes the water-quality measurements for Catherine Lake. Here is what has been measured.
- Mesotrophic
- Impaired · Mercury
- Public access
- Limited data
Catherine Lake in Lake County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 7.4 ft visibility. Phosphorus: 30 µg/L. Chlorophyll-a (algae): 4.9 µg/L.
Catherine Lake is a mesotrophic lake in Lake County, Illinois. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 3 public boat landings. Compared to the 18 other monitored lakes in Lake County, Catherine Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2022-10-17. Methodology: how these readings are compared.
What Catherine Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch3 documented ramps
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. Catherine Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, nutrients (phosphorus, nitrogen), pCBs. Check local advisories before you swim.
Whether Catherine Lake is safe to swim in today is a call for the Illinois Environmental Protection Agency and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Catherine Lake
These are the measurements Illinois EPA publishes for Catherine Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Moderate clarity, visible to about 7.4 ft. Phosphorus 30 µg/L. Chlorophyll-a 4.9 µg/L. TSI 49.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 7.4ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 30µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 4.9µg/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. | 49 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Catherine Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Catherine Lake typically sits around 58°F at the surface in October. Summer average is about 71°F. Usually warmest in Jul (about 75°F) and coldest in May (about 56°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (56°F) to its warmest (75°F).
Typical surface water temperature by month, from 443 field readings (2012–2022) via the EPA Water Quality Portal. See the full Catherine Lake water temperature breakdown →
Recreation & Access
- Fox Chain O'LakesPublic
- Lake Marie - Sequoit HarborPublic
- a marinaSemi-private
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Catherine Lake
Compare lakeside cabins, hotels, and vacation rentals near Catherine Lake in Lake County, Illinois — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Catherine Lake
Prices for Oct 23–25, 4 adults. Change dates on the map below.
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Planning a trip? Cabins and lodging at Catherine Lake → · more Illinois lake trips
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Fishing Catherine Lake
Water Quality Trend: Worsening
Based on 7 years of monitoring (2020–2026).
Water clarity
Worsening7 years
Phosphorus
Worsening+7.15 µg/L/yr3 years
EPA Impairment Status
Catherine 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: Fish consumption, Other.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IL_RTD · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Catherine 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.
- Salem Utility District No 2Salem · 1.9 mi away · NPDES WI0031496MajorRecent 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.
Nearby Lakes in Lake County
Frequently asked questions about Catherine Lake
Where is Catherine Lake?
- Catherine Lake is a lake in Lake County, Illinois. Its water-quality measurements are published by Illinois EPA and shown on this page as reported.
What is the water quality of Catherine Lake?
- Catherine Lake in Lake County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 7.4 ft visibility. Phosphorus: 30 µg/L. Chlorophyll-a (algae): 4.9 µg/L.
Is Catherine Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Catherine Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, nutrients (phosphorus, nitrogen), pCBs. Check local advisories before you swim.
What is the water temperature of Catherine Lake?
- Catherine Lake typically sits around 58°F at the surface in October, from 443 EPA Water Quality Portal field readings (2012–2022). That is a typical value for the month, not a live reading.
Are there boat ramps on Catherine Lake?
- Catherine Lake has 3 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Fox Chain O'Lakes, Lake Marie - Sequoit Harbor, a marina. Public access is listed as yes.
Can I fish at Catherine Lake?
- Catherine Lake has 3 documented boat landings in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Illinois's fish and wildlife agency, so check its current regulations before you go.
Explore Catherine Lake across LakeQuality
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 readings
Illinois's cleanest lakes, ranked on agency measurements
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Other Lakes in Illinois
Mesotrophic Lakes in Illinois
Where this data comes from
22 measurements from 2 monitoring stations, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- illinois epa
IL_EPA_WQX22 samples · 2022
Analytical methods
- MEASURED IN FIELD
- Phosphorus by Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
Monitoring station identifiers (2)
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.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Named boat-access points from the USGS National Boat Ramps inventory