Maryland’s Lakes and Reservoirs: FAQ
Q1: Is it true that Maryland does not have any natural lakes?
A1: Yes, there are no natural lakes in Maryland. All of Maryland’s
lakes are manmade by damming rivers. Some have been named lakes (e.g., Lake
Habeeb in Allegany County and Deep Creek Lake in Garrett County), but most
have been named reservoirs (e.g., Loch Raven Reservoir in Baltimore County).
Q2: Did Maryland ever have any natural lakes in the past?
A2: Yes. We know of at least one, and there could be more. The one clearly
documented case is Buckel’s Bog, which was a 160-acre, shallow periglacial
lake (actually a glade) that occupied the headwater region of the North Branch
of the Casselman River in Garrett County during the late Pleistocene (19,000-14,000
years ago). [Reference: Maxwell, J.A. and Davis, M. B., 1972, Pollen evidence
of Pleistocene and Holocene vegetation of the Allegheny Plateau, Maryland:
Quaternary Research, 2(4): 506-530.]
Q3: Why are there no natural lakes in Maryland?
A3: There are about a dozen major types of lakes, meaning there are about a
dozen ways lakes form. None of those is found in Maryland. Some 74% of all
lakes are glacial in origin, but glaciers never entered Maryland during the
last Great Ice Age. Glacial lakes may form in bedrock depressions gouged
out by glaciers or in areas where detached blocks of stagnant or retreating
ice sheets are surrounded by other glacial deposits, such as sand and gravel
outwash. When the blocks of ice melt away, the remaining depression, known
as a kettle, may fill with water to form a “kettle lake.” Other
major types of natural lakes include those that result from faulting, volcanic
activity, and landslides blocking a river.
Q4: Why are some manmade lakes called lakes while others are called reservoirs?
A4: There are no hard and fast rules about naming. However, in general, the
primary use of the manmade lake/reservoir determines what the body of water
is called. If the primary use is recreation, the body is often called a lake
(e.g., Deep Creek Lake, Greenbrier Lake, and Lake Linganore). If the primary
use is water supply, hydroelectric power, and/or flood control, the body
is more likely called a reservoir (e.g., Prettyboy Reservoir, Loch Raven
Reservoir, and Triadelphia Reservoir).
Q5: What are some characteristics of the larger reservoirs or lakes in Maryland?
A5: The following table summarizes some of the main characteristics of those
reservoirs in Maryland that have a surface area greater than one square mile.
They are listed in the order of decreasing surface area.
| Name | County | River affected | Primary Purpose | Surface Area (acres) 1 | Max. Capacity (acre ft.) 2 |
| Conowingo Reservoir | Harford & Cecil Counties + Pa. | Susquehanna River | Hydroelectric | 8,563 | 310,000 |
| Deep Creek Lake | Garrett County | Deep Creek (a tributary of the Youghiogheny River) | Hydroelectric & recreational | 3,900 | 103,350 |
| Liberty Reservoir | Baltimore & Carroll Counties | North Branch Patapsco River | Baltimore City water supply | 3,106 | 177,000 |
| Youghiogheny River Reservoir | Garrett County + Pa. (mostly in Pa.) | Youghiogheny River | Flood control & hydroelectric | 2,800 | 151,200 |
| Loch Raven Reservoir | Baltimore County | Gunpowder River | Baltimore City water supply | 2,400 | 91,900 |
| Prettyboy Reservoir | Baltimore County | Gunpowder Falls | Baltimore City water supply | 1,500 | 90,100 |
| Jennings Randolph Lake | Garrett County | North Branch Potomac River | Potomac River Flood control | 952-965 | 130,900 |
| Triadelphia Reservoir (Brighton Dam) | Montgomery County | Patuxent River | Hydroelectric | 800 | 32,300 |
| Rocky Gorge | Montgomery County | Patuxent River | Washington area water supply | 773 | 22,000 |
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Downloads and Links
FactSheet 15: Maryland’s Lakes and Reservoirs: FAQ (pdf, 14 kb).Other information on Maryland lakes: Bathymetric maps of Maryland reservoirs
Prepared by Jim Reger
Compiled by the Maryland Geological
Survey, 2300 St. Paul Street, Baltimore, MD 21218
This electronic version of "Fact Sheet No.15" was prepared by R.D.
Conkwright, Division of Coastal and Estuarine Geology, Maryland Geological
Survey.