Jacksonville Lake
Morgan County, Illinois477 acresView mapDirections
Nutrients and algae run well above the regional average.
↓ down from D at the last regrade
- Hypereutrophic
- Impaired · Mercury
- #1 of 2 in the county
- 36 ft max depth
- Public access
- Limited data
Jacksonville Lake in Morgan County, Illinois has a water quality grade of F (Algae-prone). Water clarity: 1.8 ft visibility. Phosphorus: 60.5 µg/L. Chlorophyll-a (algae): 42.2 µg/L. Surface area: 477 acres.
- Clarity
- 1.8 ft
- Max depth
- ~36 ft est.
- Area
- 477 acres
- Type
- Hypereutrophic
- Phosphorus
- 60.5 µg/L
- Chlorophyll-a
- 42.2 µg/L
- Public access
- Yes
Stays via Stay22
Stays near Jacksonville Lake
Compare lakeside cabins, hotels, and vacation rentals near Jacksonville Lake in Morgan 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 grade measures nutrients and algae, not lodging — cabins and rentals around Jacksonville Lake are listed below.
Top-rated places to stay near Jacksonville Lake
Prices for Sep 11–13, 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 Jacksonville Lake → · more Illinois lake trips
Watch Jacksonville Lake’s letter
Email me if this lake’s grade moves. Grades stay free.
Or email
Jacksonville Lake is a 477-acre highly nutrient-loaded hypereutrophic lake in Morgan County, Illinois with an estimated average depth of about 36 feet. Water quality is graded F based on 2 sampling years through 2022. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 1 other monitored lakes in Morgan County, Jacksonville Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2022-10-18. Grade methodology: LakeQuality methodology.
What Jacksonville 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. Jacksonville Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, nutrients (phosphorus, nitrogen), turbidity. Check local advisories before you swim.
Water Quality Grade: F (Algae-prone)
Very murky, less than 1.8 ft of visibility. Phosphorus 60.5 µg/L. Chlorophyll-a 42.2 µg/L. TSI 66. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.8 ft | Not graded |
| Phosphorus | 60.5 µg/L | Poor |
| Chlorophyll-a (Algae) | 42.2 µg/L | Poor |
| Trophic State Index (TSI) | 66 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~36 ft est. |
| Average Depth | ~6 ft est. |
| Surface Area | 477 acres |
| 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 Jacksonville 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
- Lake JacksonvillePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Jacksonville Lake
Reservoir Info (USACE NID)
Jacksonville Lake is a man-made reservoir impounded by the Lake Jacksonville Dam (completed 1939), built primarily for recreation on the SANDY CREEK; earth-type dam, 54 ft tall and 980 ft long.
- Surface area
- 477 ac
- Normal storage
- 6,099 ac-ft
- Max storage
- 12,812 ac-ft
- Drainage area
- 10.8 sq mi
- Hazard class
- Significant
- Owner
- CITY OF JACKSONVILLE
All listed purposes: Recreation;Water Supply.
Source: USACE National Inventory of Dams, NID ID IL00711 · Operator website
EPA Impairment Status
Jacksonville 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_RDI · Official waterbody report
County Ranking
Ranked #1 of 2 lakes in Morgan County
Nearby Lakes in Morgan County
Frequently asked questions about Jacksonville Lake
Where is Jacksonville Lake?
- Jacksonville Lake is a lake in Morgan County, Illinois. LakeQuality grades it F for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Jacksonville Lake?
- Jacksonville Lake in Morgan County, Illinois has a water quality grade of F (Algae-prone). Water clarity: 1.8 ft visibility. Phosphorus: 60.5 µg/L. Chlorophyll-a (algae): 42.2 µg/L. Surface area: 477 acres.
Is Jacksonville Lake safe to swim in?
- The F is nutrients and algae, not a swimming clearance. Jacksonville Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, nutrients (phosphorus, nitrogen), turbidity. Check local advisories before you swim.
How deep is Jacksonville Lake?
- No published bathymetric survey covers Jacksonville Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 36 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 477 acres.
Are there boat ramps on Jacksonville Lake?
- Jacksonville Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Lake Jacksonville. Public access is listed as yes.
Explore Jacksonville Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
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
Compare Jacksonville Lake With Nearby Lakes
Where this data comes from
48 measurements from 3 monitoring stations, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- illinois epa
IL_EPA_WQX48 samples · 2022
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