Midlothian Lake is a 30-acre productive, nutrient-rich eutrophic lake in Cook County, Illinois. Water quality is graded D based on 2 sampling years through 2021. Compared to the 67 other monitored lakes in Cook County, Midlothian Lake ranks #42 for water quality.
Source: EPA Water Quality Portal sampling records, Illinois DNR, last sampled 2021-09-21. Grade methodology: LakeGrade methodology.
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Swimming Safety
Swimming not recommended, poor water quality with high algae risk
Water Quality Grade: D, Poor
Very murky, less than 1.2 ft of visibility. Phosphorus level: 44.5 µg/L. Trophic State Index: 67.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.2 ft | F |
| Phosphorus | 44.5 µg/L | C |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 67 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 30 acres |
Where to stay near Midlothian Lake
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Fishing Midlothian Lake
Water Temperature
Midlothian Lake averages about 79°F at the surface in summer, usually warmest in Jul (about 81°F) and coldest in May (about 59°F). These are typical values by month — not a live reading.
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 →
Location
County Ranking
Ranked #42 of 68 lakes in Cook County
Cleaner Lakes Within 30 Miles
Midlothian Lake holds Grade D. 2 nearby lakes hold higher grades.
- BWampum LakeCook County · 7.9 mi · Two grade letters higher (D → B)
- CTurtlehead LakeCook County · 4.8 mi · Higher grade (D → C)
Nearby Lakes in Cook County
Explore Midlothian Lake across LakeGrade
More Illinois Lake Rankings
Other Grade D Lakes in Illinois
Eutrophic Lakes in Illinois
More records, surveys & data sources
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
Source: EPA ATTAINS assessment unit IL_RHZI · Official waterbody report
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
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)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2021-09-21
Monitoring stations: 1