Largest Reservoirs in Maryland

Maryland has 391 dams with recorded storage capacity. The largest is Conowingo with 310,000 acre-feet of maximum storage. One acre-foot equals about 326,000 gallons — enough to supply roughly two households for a year.

#	Dam	County	Max Storage (acre-ft)	Height (ft)	Purpose	Year
1	Conowingo	Cecil	310,000	94	Hydroelectric	1928
2	Liberty Dam	Baltimore	177,000	175	Water Supply	1953
3	Loch Raven Dam	Baltimore	145,000	130	Water Supply	1923
4	Deep Creek Dam	Garrett	145,000	85	Hydroelectric	1925
5	Jennings Randolph Dam	Mineral	130,900	296	Flood Risk Reduction	1981
6	Prettyboy Dam	Baltimore	90,100	155	Water Supply	1936
7	T. Howard Duckett Dam	Howard	59,000	139	Water Supply	1953
8	Savage River Dam	Garrett	31,800	184	Flood Risk Reduction	1952
9	Little Seneca Dam	Montgomery	24,185	99	Water Supply	1984
10	Brighton	Montgomery	19,560	82	Hydroelectric	1943
11	Little Falls Dam - Potomac River	Montgomery	13,360	12	Water Supply	1958
12	Rocky Gap Dam	Allegany	10,048	98	Water Supply	1969
13	St Marys River Watershed Site 1	St. Mary's	9,600	38	Recreation	1975
14	Piney Run Dam	Carroll	8,842	73	Water Supply	1974
15	Lake Linganore	Frederick	7,900	63	Recreation	1972
16	Lake Frank	Montgomery	7,854	78	Recreation	1967
17	Lake Needwood	Montgomery	7,023	65	Recreation	1965
18	Potomac River Dam #4	Washington	6,750	20	Hydroelectric	1869
19	Little Youghiogheny Site 6 (broadford)	Garrett	5,000	60	Water Supply	1971
20	Potomac Dam No. 5	Washington	4,900	20	Fish and Wildlife Pond	1830
21	Gilbert Run Dam 1 (trinity Church)	Charles	4,840	41	Flood Risk Reduction	1964
22	Cox Creek Dmcf	Anne Arundel	4,000	36	Tailings	1960
23	Masonville Dmcf	Baltimore City	4,000	18	Tailings
24	Frostburg Reservoir	Garrett	3,276	46	Water Supply	1990
25	Gilbert Run Dam 3 (jameson Dam)	Charles	2,900	37	Flood Risk Reduction	1964
26	Seneca State Park Dam (seneca Creek Road)	Montgomery	2,792	64	Recreation	1975
27	Chesapeake Ranch Estates Dam (chisolm Trail)	Calvert	2,614	46	Recreation	1965
28	Atkisson Reservoir	Harford	2,510	59	Water Supply	1942
29	York Bldg Products Settling Pond 12	Cecil	2,062	70	Tailings	2004
30	Johnsons Pond	Wicomico	1,930	23	Recreation	1936
31	Druid Hill Lake Reservoir And Storage Tanks	Baltimore City	1,880	118	Water Supply	1871
32	Lake Roland Dam	Baltimore	1,867	42	Recreation	1861
33	Lake Montebello	Baltimore City	1,860	30	Other	1880
34	Gilbert Run Dam 2 (wheatley)	Charles	1,850	37	Recreation	1968
35	Prince George Country Club Dam (pleasant Prospect)	Prince George's	1,550	30	Recreation	1982
36	Centennial Park Dam	Howard	1,519	42	Recreation	1985
37	Daniels Dam	Baltimore	1,500	27	Recreation	1833
38	Little Youghiogheny Site 5	Garrett	1,500	45	Flood Risk Reduction	1968
39	Industrial Dam (blue Bridge)	Allegany	1,467	40	Water Supply	1954
40	Hunting Creek Dam	Frederick	1,263	79	Water Supply	1969
41	Wye Mills Dam	Queen Anne's	1,224	20	Recreation	1682
42	Tuckahoe State Park Dam (crouse Mill Road)	Queen Anne's	1,210	14	Recreation	1975
43	York Bldg Products Settling Pond 13	Cecil	1,178	45	Tailings	2016
44	Little Youghiogheny Site 7	Garrett	1,155	45	Flood Risk Reduction	1960
45	Broad Creek Dam	Harford	958	36	Recreation	1948
46	Lake Whetstone Dam (montgomery Village Avenue)	Montgomery	930	36	Recreation	1966
47	Victoria Station Community Lake	Calvert	920	27	Recreation	1986
48	Lake Elkhorn	Howard	910	26	Recreation	1974
49	Beaglin Park Dam (beaglin Park Drive)	Wicomico	879	23	Recreation	1976
50	Hurlock Oxidation Ponds	Dorchester	859	24	Other	1968

← All dams in Maryland · Largest reservoirs nationwide