Salem Lake is a 78-acre highly nutrient-loaded hypereutrophic lake in Marion County, Illinois. Water quality is graded F based on 2 sampling years through 2022. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 5 other monitored lakes in Marion County, Salem Lake ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, Illinois DNR, last sampled 2022-10-19. Grade methodology: LakeGrade methodology.
Watch Salem Lake water quality
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Swimming Safety
Avoid swimming, very poor water quality, potential algae toxins
Water Quality Grade: F, Very Poor
Very murky, less than 1 ft of visibility. Phosphorus level: 197 µg/L. Trophic State Index: 79.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1 ft | F |
| Phosphorus | 197 µg/L | F |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 79 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 78 acres |
| Public Access | Yes |
Where to stay near Salem Lake
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Fishing Salem Lake
Water Quality Trend: ↑ Improving
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +1 m/yr | 2 |
| Phosphorus | ↑ Improving | -14 µg/L/yr | 2 |
Recreation & Access
Water Temperature
Salem Lake averages about 81°F at the surface in summer, usually warmest in Jul (about 82°F) and coldest in Oct (about 58°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 234 field readings (2010–2022) via the EPA Water Quality Portal. See the full Salem Lake water temperature breakdown →
Location
County Ranking
Ranked #4 of 6 lakes in Marion County
Cleaner Lakes Within 30 Miles
Salem Lake holds Grade F. 3 nearby lakes hold higher grades.
- DKinmundy New LakeMarion County · 9.3 mi · Higher grade (F → D)
- DCentralia LakeMarion County · 6.8 mi · Higher grade (F → D)
- DForbes LakeMarion County · 11.4 mi · Higher grade (F → D)
Nearby Lakes in Marion County
Explore Salem Lake across LakeGrade
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
Illinois's cleanest and most-polluted lakes, ranked
More Illinois Lake Rankings
Other Grade F Lakes in Illinois
Hypereutrophic Lakes in Illinois
More records, surveys & data sources
Reservoir Info (USACE NID)
Salem Lake is a man-made reservoir impounded by the Salem Reservoir Dam (completed 1912), built primarily for recreation on the TOWN CREEK; earth-type dam, 21 ft tall and 775 ft long.
- Surface area
- 78 ac
- Normal storage
- 388 ac-ft
- Max storage
- 900 ac-ft
- Drainage area
- 3.9 sq mi
- Hazard class
- High
- Owner
- CITY OF SALEM
All listed purposes: Recreation;Water Supply.
Source: USACE National Inventory of Dams, NID ID IL00245 · Operator website
EPA Impairment Status
Salem 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_ROR · Official waterbody report
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
3 EPA-permitted facilities operate within about 5 miles of Salem 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 Stp, City OfSalem · 2.1 mi away · NPDES IL0023264MajorRecent violation
- Union Pacific Railroad-SalemSalem · 1.7 mi away · NPDES IL0000361
- Salem Municipal Landfill #2Salem · 2 mi away · NPDES IL0075621
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.
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2022-10-19
Monitoring stations: 3