Long Lake
Lake County, IllinoisView mapDirections
Illinois EPA publishes the water-quality measurements for Long Lake. Here is what has been measured.
- Hypereutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- 53 ft max depth
- Public access
Long Lake in Lake County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 3.4 ft visibility. Phosphorus: 81 µg/L. Chlorophyll-a (algae): 57.1 µg/L.
Long Lake is a highly nutrient-loaded hypereutrophic lake in Lake County, Illinois with an estimated average depth of about 53 feet. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 2 public boat landings. Compared to the 18 other monitored lakes in Lake County, Long Lake ranks #12 for water quality.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2024-02-21. Methodology: how these readings are compared.
Long Lake has 2 public boat landings, so a lakefront rental is not the only way to get a boat on the water. Vrbo is where to look for cabins and lake homes around Long Lake, and Booking.com and Expedia search hotels near the lake for your dates.
What Long Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch2 documented ramps
Swimming conditions
Readings onlyAlgae risk
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. Long Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Long 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 Long Lake
These are the measurements Illinois EPA publishes for Long Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Murky, only visible to about 3.4 ft. Phosphorus 81 µg/L. Chlorophyll-a 57.1 µg/L. TSI 66.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 3.4ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 81µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 57.1µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 66 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Long Lake
Answers come straight from the public measurements and survey records on this page.
Current Conditions
USGS snapshot Jul 1, 2026, 4:30 PM from gauge 423784088133401 (Long Lake at Ben Dock at Long Lake, IL). Station page ↗ — a live reading replaces this snapshot when the gauge responds. Missing live data is not an all-clear.
Water Temperature
Long Lake typically sits around 60°F at the surface in October. Summer average is about 76°F. Usually warmest in Jul (about 80°F) and coldest in Feb (about 38°F). These are typical values by month — see Current Conditions above for the latest gauge reading.
Column height runs from this lake’s coldest month (38°F) to its warmest (80°F).
Typical surface water temperature by month, from 177 field readings (2012–2024) via the EPA Water Quality Portal. See the full Long Lake water temperature breakdown →
Lake Details
Max depth
~53 ft est.
Public access
Yes
Listed by Illinois EPA
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Illinois has not published bathymetry for Long Lake.
Lake Size & Watershed
Watershed (drainage) area
36 sq mi
HydroLAKES / HydroSHEDS
Surface area
351 acres
HydroLAKES / HydroSHEDS
Shoreline
4.1 mi
HydroLAKES / HydroSHEDS
Elevation
735 ft
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.
Recreation & Access
- Long Lake boat launchPublic
- Swanys On Long Lake MarinaPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Long Lake
Compare lakeside cabins, hotels, and vacation rentals near Long 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. The water-quality readings cover nutrients and algae, not lodging. Cabins and rentals around Long Lake are listed below.
Top-rated places to stay near Long Lake
Prices for Oct 23–25, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a trip? Cabins and lodging at Long Lake → · more Illinois lake trips
Follow Long Lake’s readings
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Fishing Long Lake
Water quality readings over time
2 seasons of samples on record (2022–2023). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Worsening2 years
Phosphorus
Improving-26.5 µg/L/yr2 years
Chlorophyll-a
Improving-18.8 µg/L/yr2 years
EPA Impairment Status
Long Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Other.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IL_RTJ · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Long Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Camp Henry Horner StpIngleside · 2.1 mi away · NPDES IL0054615Recent 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 Long Lake
Where is Long Lake?
- Long 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 Long Lake?
- Long Lake in Lake County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 3.4 ft visibility. Phosphorus: 81 µg/L. Chlorophyll-a (algae): 57.1 µg/L.
Is Long Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Long Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Long Lake?
- Long Lake typically sits around 60°F at the surface in October, from 177 EPA Water Quality Portal field readings (2012–2024). That is a typical value for the month, not a live reading. A USGS gauge on this lake last read 83°F.
How deep is Long Lake?
- No published bathymetric survey covers Long Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 53 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Are there boat ramps on Long Lake?
- Long Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Long Lake boat launch, Swanys On Long Lake Marina. Public access is listed as yes.
Can I fish at Long Lake?
- Long Lake has 2 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 Long 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
More lakes in Illinois
Other Lakes in Illinois
Hypereutrophic Lakes in Illinois
Where this data comes from
76 measurements from 4 monitoring stations, 2022–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- USGS Illinois Water Science Center
USGS-IL40 samples · 2022–2024 - illinois epa
IL_EPA_WQX36 samples · 2022
Analytical methods
- Secchi disk method
- Nutrients, wu, WCA,persulfate,CF
- Plant pigments, sonication & 445
- YSI EXO turbidity sensor, FNU
- MEASURED IN FIELD
- Phosphorus by Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
Monitoring station identifiers (4)
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)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Named boat-access points from the USGS National Boat Ramps inventory