Saganashkee Slough Lake
Cook County, IllinoisView mapDirections
Nutrients and algae run well above the regional average.
- Hypereutrophic
- Impaired · Algal growth
- #11 of 16 in the county
- 56 ft max depth
- Public access
- Limited data
Saganashkee Slough Lake in Cook County, Illinois has a water quality grade of F (Algae-prone). Water clarity: 0.8 ft visibility. Phosphorus: 170 µg/L. Chlorophyll-a (algae): 108.5 µg/L.
- Clarity
- 0.8 ft
- Typical in September
- 71°F
- Max depth
- ~56 ft est.
- Type
- Hypereutrophic
- Public access
- Yes
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Saganashkee Slough Lake is a highly nutrient-loaded hypereutrophic lake in Cook County, Illinois with an estimated average depth of about 56 feet. Water quality is graded F based on 2 sampling years through 2020. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 15 other monitored lakes in Cook County, Saganashkee Slough Lake ranks #11 for water quality.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2020-10-20. Grade methodology: LakeQuality methodology.
What Saganashkee Slough Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Swimming Safety
Grade onlyLimited data
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
The F is nutrients and algae, not a swimming clearance. Saganashkee Slough Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, metals (other than mercury), nutrients (phosphorus, nitrogen), pCBs, sediment / turbidity, turbidity. Check local advisories before you swim.
Water Quality Grade: F (Algae-prone)
Very murky, less than 0.8 ft of visibility. Phosphorus 170 µg/L. Chlorophyll-a 108.5 µg/L. TSI 79. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 0.8 ft | Not graded |
| Phosphorus | 170 µg/L | Poor |
| Chlorophyll-a (Algae) | 108.5 µg/L | Poor |
| Trophic State Index (TSI) | 79 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Water Temperature
Saganashkee Slough Lake typically sits around 71°F at the surface in September. Summer average is about 80°F. Usually warmest in Jul (about 83°F) and coldest in Oct (about 55°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 22 field readings (2010–2022) via the EPA Water Quality Portal. See the full Saganashkee Slough Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~56 ft est. |
| Average Depth | ~15 ft est. |
| Public Access | Yes |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Illinois has not published bathymetry for Saganashkee Slough Lake.
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.
Recreation & Access
- Saganashkee Slough boat launchPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Saganashkee Slough Lake
Reservoir Info (USACE NID)
Saganashkee Slough Lake is a man-made reservoir impounded by the Saganashkee Slough 1 Dam (completed 1948), built primarily for recreation on the TRIB CALUMET SAG CHANNEL; earth-type dam, 14 ft tall and 950 ft long.
- Normal storage
- 718 ac-ft
- Max storage
- 2,379 ac-ft
- Hazard class
- Significant
- Owner
- FOREST PRESERVE DISTRICT OF COOK COUNTY
Source: USACE National Inventory of Dams, NID ID IL00870 · Operator website
EPA Impairment Status
Saganashkee Slough 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_RHH · Official waterbody report · Matched by proximity (0.05 km)
County Ranking
Ranked #11 of 16 lakes in Cook County
Nearby Lakes in Cook County
Frequently asked questions about Saganashkee Slough Lake
Where is Saganashkee Slough Lake?
- Saganashkee Slough Lake is a lake in Cook County, Illinois. LakeQuality grades it F for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Saganashkee Slough Lake?
- Saganashkee Slough Lake in Cook County, Illinois has a water quality grade of F (Algae-prone). Water clarity: 0.8 ft visibility. Phosphorus: 170 µg/L. Chlorophyll-a (algae): 108.5 µg/L.
Is Saganashkee Slough Lake safe to swim in?
- The F is nutrients and algae, not a swimming clearance. Saganashkee Slough Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, metals (other than mercury), nutrients (phosphorus, nitrogen), pCBs, sediment / turbidity, turbidity. Check local advisories before you swim.
What is the water temperature of Saganashkee Slough Lake?
- Saganashkee Slough Lake typically sits around 71°F at the surface in September, from 22 EPA Water Quality Portal field readings (2010–2022). That is a typical value for the month, not a live reading.
How deep is Saganashkee Slough Lake?
- No published bathymetric survey covers Saganashkee Slough Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 56 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 Saganashkee Slough Lake?
- Saganashkee Slough Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Saganashkee Slough boat launch. Public access is listed as yes.
Explore Saganashkee Slough Lake across LakeQuality
Species activity outlook by water temperature and season
Where to stay at Illinois's top lakes, each with its grade
Very high nutrients, dense algae, poor clarity
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Where this data comes from
48 measurements from 3 monitoring stations, 2020. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- illinois epa
IL_EPA_WQX48 samples · 2020
Analytical methods
- MEASURED IN FIELD
- Phosphorus by Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
Monitoring station identifiers (3)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Named boat-access points from the USGS National Boat Ramps inventory