State · United States · USGS · BOR · USACE · CDEC
Illinois
94% average fill
Measured
4
Volume stored
551 hm³
Measured capacity
586 hm³
Critical
1
Low level
1
Loading map…
Reservoirs
Sorted by capacityCarlyle Pool
Updated 2026-08-03
Rend Pool
Updated 2026-08-03
Sub
lowUpdated 2026-08-03
Sub Casey
criticalUpdated 2026-08-03
Storage from official US gauges (USGS, USACE, Bureau of Reclamation, CDEC). Fill % uses design capacity from the National Inventory of Dams where available; a few sites without a match fall back to the 5-year maximum.
About reservoirs in Illinois
As of August 3, 2026, the reservoirs we track across Illinois that report live levels hold roughly 551 hm³ of water — about 94.0% of their combined capacity. Taken together, Illinois's reservoirs are high.
Across the region, 1 reservoir is at critically low levels and 1 is low. Rend Pool is the fullest at 101.8%, while Sub Casey is the lowest at 11.3%.
Storage figures for Illinois come from USGS · USACE · BOR · CDEC; the most recent reading is from August 3, 2026. Each reservoir below links to its own page with full history and seasonal context.
Illinois at a glance
- Reservoirs tracked
- 4
- Average fill
- 94.0%
- Water stored
- 551 hm³
- Combined capacity
- 586 hm³
- At critically low levels
- 1
- Fullest
- Rend Pool (101.8%)
- Lowest
- Sub Casey (11.3%)
- Last updated
- August 3, 2026
Frequently asked questions
How full are reservoirs in Illinois right now?
As of August 3, 2026, the reservoirs tracked in Illinois that report live levels are 94.0% full overall, holding about 551 hm³ of water.
How many reservoirs are there in Illinois?
reservoirs.earth tracks 4 reservoirs in Illinois, with a combined storage capacity of 586 hm³.
Which reservoir in Illinois is the fullest?
Rend Pool is currently the fullest reservoir in Illinois, at 101.8% of capacity.
Which reservoir in Illinois is the lowest?
Sub Casey is currently the lowest in Illinois, at 11.3% of capacity.
Where does the reservoir data for Illinois come from?
All storage figures for Illinois come from USGS · USACE · BOR · CDEC, an official source, last updated August 3, 2026.