Midlothian Lake
Cook County, Illinois30 acresView mapDirections
Illinois EPA publishes the water-quality measurements for Midlothian Lake. Here is what has been measured.
- Hypereutrophic
- Impaired · Mercury
- 49 ft max depth
- Limited data
Midlothian Lake in Cook County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 1.2 ft visibility. Phosphorus: 121 µg/L. Chlorophyll-a (algae): 61.5 µg/L. Surface area: 30 acres.
Midlothian Lake is a 30-acre highly nutrient-loaded hypereutrophic lake in Cook County, Illinois with an estimated average depth of about 49 feet. Compared to the 15 other monitored lakes in Cook County, Midlothian Lake ranks #16 for water quality.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2021-09-21. Methodology: how these readings are compared.
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. Midlothian Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, nutrients (phosphorus, nitrogen), pesticides, pCBs. Check local advisories before you swim.
Whether Midlothian 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 Midlothian Lake
These are the measurements Illinois EPA publishes for Midlothian Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 1.2 ft of visibility. Phosphorus 121 µg/L. Chlorophyll-a 61.5 µg/L. TSI 73.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 1.2ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 121µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 61.5µg/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. | 73 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Midlothian Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Midlothian Lake typically sits around 65°F at the surface in October. Summer average is about 79°F. Usually warmest in Jul (about 81°F) and coldest in May (about 59°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (59°F) to its warmest (81°F).
Typical surface water temperature by month, from 35 field readings (2016–2022) via the EPA Water Quality Portal. See the full Midlothian Lake water temperature breakdown →
Lake Details
Max depth
~49 ft est.
Surface area
30 acres
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Illinois has not published bathymetry for Midlothian Lake.
Lake Size & Watershed
Watershed (drainage) area
2 sq mi
HydroLAKES / HydroSHEDS
Shoreline
1.2 mi
HydroLAKES / HydroSHEDS
Elevation
653 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.
Stays via Stay22
Stays near Midlothian Lake
Compare lakeside cabins, hotels, and vacation rentals near Midlothian Lake in Cook 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 Midlothian Lake are listed below.
Top-rated places to stay near Midlothian 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 whole trip? See where to stay at Illinois’s top lakes →
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Fishing Midlothian Lake
Reservoir Info (USACE NID)
Midlothian Lake is a man-made reservoir impounded by the Midlothian Creek Dam (completed 1975), built primarily for flood risk reduction on the MIDLOTHIAN CREEK; earth-type dam, 22 ft tall and 1,515 ft long.
- Surface area
- 30 ac
- Normal storage
- 148 ac-ft
- Max storage
- 1,279 ac-ft
- Drainage area
- 10.7 sq mi
- Hazard class
- High
- Owner
- ILLINOIS DEPARTMENT OF NATURAL RESOURCES
All listed purposes: Flood Risk Reduction;Recreation.
Source: USACE National Inventory of Dams, NID ID IL01002 · Operator website · Matched by proximity (0.3 km)
EPA Impairment Status
Midlothian 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.
Source: EPA ATTAINS assessment unit IL_RHZI · Official waterbody report
Nearby Lakes in Cook County
Frequently asked questions about Midlothian Lake
Where is Midlothian Lake?
- Midlothian Lake is a lake in Cook County, Illinois. Its water-quality measurements are published by Illinois EPA and shown on this page as reported.
What is the water quality of Midlothian Lake?
- Midlothian Lake in Cook County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 1.2 ft visibility. Phosphorus: 121 µg/L. Chlorophyll-a (algae): 61.5 µg/L. Surface area: 30 acres.
Is Midlothian Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Midlothian Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, nutrients (phosphorus, nitrogen), pesticides, pCBs. Check local advisories before you swim.
What is the water temperature of Midlothian Lake?
- Midlothian Lake typically sits around 65°F at the surface in October, from 35 EPA Water Quality Portal field readings (2016–2022). That is a typical value for the month, not a live reading.
How deep is Midlothian Lake?
- No published bathymetric survey covers Midlothian Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 49 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate. The lake covers 30 acres.
Explore Midlothian Lake across LakeQuality
Planning a trip around Indiana Dunes?
Midlothian Lake is about 33 miles from Indiana Dunes National Park. Crowds there swing hard by season, so the month you pick changes both how busy the park is and what lodging costs.
Best time to visit Indiana Dunes →More lakes in Illinois
Other Lakes in Illinois
Hypereutrophic Lakes in Illinois
Where this data comes from
16 measurements from 1 monitoring station, 2021. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- illinois epa
IL_EPA_WQX16 samples · 2021
Analytical methods
- MEASURED IN FIELD
- Phosphorus by Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
Monitoring station identifiers (1)
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
Lake size & watershed from HydroLAKES (HydroSHEDS)