St Marys Lake water level — Maryland
St Marys Lake in Maryland was last measured at 58.80 ft (datum NAVD88), as of Aug 31, 2026, 4:05 AM (UTC-04:00) (USGS Water Services). Over its recent trend window the level has been steady (+0.0 ft). This reading is provisional and subject to revision.
- % of conservation pool full
- Not reported
- Storage
- Not reported
- Recent trend
- →Steady
+0.0 ft over the trend window
Recent trend
Readings this station published between Jun 2, 2026 and Aug 31, 2026 — a 89-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: USGS site 01661499, retrieved Aug 31, 2026, 8:24 AM (UTC+00:00). Official page for this lake →
About this gauge's record
This site's drainage basin covers approximately 9 sq mi of contributing watershed.
The dam behind St Marys Lake
St Marys Lake is held back by St Marys River Watershed Site 1 (also recorded as St Marys River State Park Dam) , an earthfill embankment, holding the pool back by sheer mass and an impervious core rather than by the strength of concrete , standing 38 ft high and running 1,670 ft along its crest , built across Western Br, St. Marys River in St. Mary's County , near Great Mills . It was completed in 1975 and modified in 1975 , and is owned by MD DNR-Public Lands, Engineering & Constr-Southern (a state owner) , to a design credited to ALLAN STAHL;USDA NRCS;USDA SCS-Allan Stahl.
Its recorded primary purpose is recreation — holding a stable pool through the season is an operating goal, so a level well off normal in summer is unusual rather than routine . It also serves recreation;other;flood risk reduction.
It is founded on soil, with a earth core. Its spillway is ungated: once the pool reaches the crest, water leaves on its own and the operator cannot hold it back. The spillway opening is 300 ft wide. Its outlet works use slide (sluice gate).
NID classes it high hazard potential. That describes what a failure would cost downstream — loss of life would be expected — and says nothing about how likely a failure is, or what condition the dam is in. Its most recent condition assessment was fair: sound under normal loading, though a rare or extreme event could expose a deficiency. That assessment is dated 11/15/2024.
At its normal pool the reservoir covers about 250 acres. NID records a maximum storage of 9,600 acre-ft against a normal storage of 3,200 acre-ft. Its maximum discharge capacity is 20,576 cubic feet per second. It is regulated by MD Dam Safety.
Dam facts: National Inventory of Dams record MD00028 , filed by Maryland — U.S. Army Corps of Engineers, public domain. Water levels above come from USGS Water Services and are a separate source. (How this dam was matched to this gauge →)
How St Marys Lake compares nearby
4 of 6 nearby lakes with a current trend are also steady right now.
Nearby lakes
The six nearest published lakes by centroid distance (great-circle) — cross-state neighbors included.
| Lake | State | Level | Distance |
|---|---|---|---|
| Hearns Pond | DE | 24.66 ft | 95 km |
| Haven Lake Outlet at Milford | DE | 13.85 ft | 120 km |
| Unnamed Pond at Dafb at Dover | DE | 2.03 ft | 133 km |
| Lake Serene at Edgewood | MD | 52.89 ft | 133 km |
| Garrisons Lake | DE | 5.51 ft | 137 km |
| Aiww A&c N Landing Bridge | VA | 0.18 ft | 175 km |
Frequently asked questions
- What is the current water level of St Marys Lake?
- As of Aug 31, 2026, 4:05 AM (UTC-04:00), the pool elevation was 58.80 ft (datum NAVD88), provisional and subject to revision. See the trend chart above for the recent direction.
- Is St Marys Lake 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 USGS site 01661499, retrieved Aug 31, 2026, 8:24 AM (UTC+00:00).
More in Maryland
See every lake tracked in Maryland, or read the methodology behind these figures.