Nav Pool water level — Illinois
Nav Pool in Illinois was last measured at 368.91 ft (datum NAVD88), as of Jul 29, 2026, 1:00 PM (UTC+00:00) (USACE CWMS Data). Over its recent trend window the level has been falling (−1.3 ft).
- % of conservation pool full
- Not reported
- Storage
- Not reported
- Recent trend
- ↓Falling
−1.3 ft over the trend window
Recent trend
Readings this station published between Jun 2, 2026 and Jul 29, 2026 — a 57-day window — downsampled for display.
Data: USGS Water Services (waterservices.usgs.gov) and USACE CWMS Data (cwms-data.usace.army.mil), retrieved 2026-08-31. Both public domain (a work of the U.S. Government, 17 U.S.C. §105).
Source: USACE MVS/Nav Pool-Kaskaskia, retrieved Aug 31, 2026, 8:24 AM (UTC+00:00). Official page for this lake →
The dam behind Nav Pool
Nav Pool is held back by Jerry F. Costello Lock and Dam (also recorded as Kaskaskia Lock and Dam; Kaskaskia Lock & Dam;Kaskaskia River) , a concrete structure , standing 81 ft high and running 603 ft along its crest , built across KASKASKIA RIVER in Randolph County , near Modoc . It was completed in 1974 , and is owned by USACE - St. Louis District (a federal owner) , to a design credited to CEMVS.
Its recorded primary purpose is navigation — the pool is held inside a narrow band to keep a navigable depth, so large swings are rare by design . It also serves navigation;fish and wildlife pond;recreation.
It is founded on soil, with a concrete core. Its spillway is gated, so the operator can hold the pool above the spillway crest and meter what leaves. The spillway opening is 120 ft wide.
NID classes it significant hazard potential: a failure would be expected to damage property and infrastructure rather than cost lives. It is a consequence rating, not a condition rating.
At its normal pool the reservoir covers about 2,618 acres. NID records a maximum storage of 25,246 acre-ft against a normal storage of 22,183 acre-ft. Its maximum discharge capacity is 62,000 cubic feet per second.
Dam facts: National Inventory of Dams record IL00115 , filed by US Army Corps of Engineers — U.S. Army Corps of Engineers, public domain. Water levels above come from USACE CWMS Data and are a separate source. (How this dam was matched to this gauge →)
How Nav Pool compares nearby
All 6 nearby lakes with a current trend are also falling, suggesting a regional pattern rather than an operation specific to this dam.
Nearby lakes
The six nearest published lakes by centroid distance (great-circle) — cross-state neighbors included.
| Lake | State | Level | Distance |
|---|---|---|---|
| Nav Tw | IL | 352.50 ft | 0 km |
| Hecker | IL | 402.08 ft | 38 km |
| Freeburg | IL | 381.30 ft | 47 km |
| Desloge | MO | 654.22 ft | 51 km |
| Sand Ridge | IL | 337.01 ft | 53 km |
| Bonne Terre | MO | 631.27 ft | 55 km |
Frequently asked questions
- What is the current water level of Nav Pool?
- As of Jul 29, 2026, 1:00 PM (UTC+00:00), the pool elevation was 368.91 ft (datum NAVD88). See the trend chart above for the recent direction.
- Is Nav Pool full right now?
- Its managing agency does not publish a %-of-conservation-pool-full figure for this lake, so we show the bare level rather than estimate one.
- Where does this data come from?
- From USACE MVS/Nav Pool-Kaskaskia, retrieved Aug 31, 2026, 8:24 AM (UTC+00:00).
More in Illinois
See every lake tracked in Illinois, or read the methodology behind these figures.