Dalecarlia Reservoir
Dalecarlia Reservoir is the primary storage basin for drinking water in Washington, D.C., and Arlington County, Virginia. The reservoir is fed by an underground aqueduct in turn fed by low dams which divert portions of the Potomac River near Great Falls and Little Falls.[2] The reservoir is located between Spring Valley and the Palisades, two neighborhoods in Northwest Washington, D.C., and Brookmont, a neighborhood in Montgomery County, Maryland.
| Dalecarlia Reservoir | |
|---|---|
  Dalecarlia Reservoir  Dalecarlia Reservoir | |
 Dalecarlia Reservoir | |
| Location | Bethesda, Maryland / Washington, D.C., U.S. |
| Coordinates | 38°56′33.0216″N 77°6′36.1548″W |
| Type | Reservoir |
| Primary inflows | Washington Aqueduct |
| Basin countries | United States |
| Surface area | 50 acres (20 ha) |
| Surface elevation | 148 ft (45 m)[1] |
History
The 50-acre (200,000 m2) reservoir was completed in 1858 by the United States Army Corps of Engineers (USACE) as part of the Washington Aqueduct project.[3] It began providing water on January 3, 1859.[4] Initially the reservoir provided water to the city from the adjacent Little Falls Branch until the aqueduct construction was completed. Regular water service from the Potomac River source through the aqueduct commenced in 1864. The reservoir was modified in 1895 and 1935 to improve water quality and increase water supply.[5]: 75, 99
In the 1920s a water purification plant was built adjacent to the reservoir. The rapid sand filter plant began operation in 1927.[5]: 101–105 [6]
In 1942, the headquarters of the Army Map Service was established on the grounds adjacent to the reservoir; several buildings constructed in the 1940s still exist. In 1946, its headquarters moved to the nearby Sumner Site, which is today the Intelligence Community Campus-Bethesda.[7]
Until the early 21st century, the semi-solid residuals (sludge) produced by the treatment plant were periodically discharged to the Potomac River. The U.S. Environmental Protection Agency (EPA) required USACE to halt most of these discharges, and a residuals handling facility was built on site, which went into operation in 2012.[8][9]
Current operation
The reservoir and water treatment plant are operated by the Washington Aqueduct, Baltimore District, U.S. Army Corps of Engineers.[10]
Climate
According to the Köppen Climate Classification system, the area has a humid subtropical climate, abbreviated "Cfa" on climate maps. The hottest temperature recorded at Dalecarlia Reservoir was 105 °F (40.6 °C) on August 17, 1997, while the coldest temperature recorded was −11 °F (−23.9 °C) on January 21, 1985.[11]
| Climate data for Dalecarlia Reservoir, Maryland, 1991–2020 normals, extremes 1948–present | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Record high °F (°C) | 79 (26) |
82 (28) |
91 (33) |
95 (35) |
98 (37) |
100 (38) |
103 (39) |
105 (41) |
99 (37) |
95 (35) |
87 (31) |
82 (28) |
105 (41) |
| Mean maximum °F (°C) | 65.7 (18.7) |
68.0 (20.0) |
77.9 (25.5) |
87.1 (30.6) |
91.9 (33.3) |
96.0 (35.6) |
98.0 (36.7) |
96.6 (35.9) |
92.1 (33.4) |
84.4 (29.1) |
75.3 (24.1) |
67.2 (19.6) |
99.3 (37.4) |
| Average high °F (°C) | 42.9 (6.1) |
46.4 (8.0) |
54.8 (12.7) |
67.6 (19.8) |
75.7 (24.3) |
84.0 (28.9) |
88.2 (31.2) |
86.2 (30.1) |
79.4 (26.3) |
68.0 (20.0) |
56.4 (13.6) |
46.9 (8.3) |
66.4 (19.1) |
| Daily mean °F (°C) | 34.2 (1.2) |
36.8 (2.7) |
44.2 (6.8) |
55.6 (13.1) |
64.7 (18.2) |
73.4 (23.0) |
78.1 (25.6) |
76.3 (24.6) |
69.3 (20.7) |
57.4 (14.1) |
46.4 (8.0) |
38.3 (3.5) |
56.2 (13.5) |
| Average low °F (°C) | 25.5 (−3.6) |
27.3 (−2.6) |
33.5 (0.8) |
43.6 (6.4) |
53.7 (12.1) |
62.8 (17.1) |
68.0 (20.0) |
66.3 (19.1) |
59.2 (15.1) |
46.8 (8.2) |
36.4 (2.4) |
29.6 (−1.3) |
46.1 (7.8) |
| Mean minimum °F (°C) | 9.2 (−12.7) |
13.2 (−10.4) |
18.5 (−7.5) |
29.0 (−1.7) |
39.2 (4.0) |
50.1 (10.1) |
57.6 (14.2) |
55.3 (12.9) |
45.6 (7.6) |
31.9 (−0.1) |
22.4 (−5.3) |
16.3 (−8.7) |
7.8 (−13.4) |
| Record low °F (°C) | −11 (−24) |
−1 (−18) |
5 (−15) |
17 (−8) |
23 (−5) |
30 (−1) |
42 (6) |
41 (5) |
31 (−1) |
16 (−9) |
8 (−13) |
−2 (−19) |
−11 (−24) |
| Average precipitation inches (mm) | 3.32 (84) |
3.24 (82) |
4.15 (105) |
3.53 (90) |
4.44 (113) |
4.24 (108) |
5.11 (130) |
4.42 (112) |
4.54 (115) |
4.40 (112) |
3.32 (84) |
3.81 (97) |
48.52 (1,232) |
| Average snowfall inches (cm) | 2.9 (7.4) |
1.4 (3.6) |
0.7 (1.8) |
0.0 (0.0) |
0.0 (0.0) |
0.0 (0.0) |
0.0 (0.0) |
0.0 (0.0) |
0.0 (0.0) |
0.0 (0.0) |
0.0 (0.0) |
0.8 (2.0) |
5.8 (14.8) |
| Average precipitation days (≥ 0.01 in) | 10.0 | 9.3 | 11.5 | 11.1 | 11.7 | 10.1 | 10.3 | 9.5 | 9.5 | 9.4 | 9.4 | 11.0 | 122.8 |
| Average snowy days (≥ 0.1 in) | 1.5 | 1.1 | 0.5 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.7 | 3.8 |
| Source 1: NOAA[12] | |||||||||||||
| Source 2: National Weather Service[11] | |||||||||||||
References
- U.S. Geological Survey Geographic Names Information System: Dalecarlia Reservoir
- "Washington Aqueduct, District of Columbia, VA and MD; Fact Sheet". Baltimore, MD: U.S. Army Corps of Engineers, Baltimore District. 2023-02-21.
- Proposed Water Treatment Residuals Management Process for the Washington Aqueduct: Environmental Impact Statement. Vol. 1 (PDF) (Report). Washington, D.C.: Washington Aqueduct Division, Baltimore District, U.S. Army Corps of Engineers (USACE). 2005. p. 3-32. Archived from the original (PDF) on 2013-02-16.
- Ways, Harry C. (2001). "Montgomery C. Meigs and the Washington Aqueduct". In Dickinson, William C.; Herrin, Dean A.; Kennon, Donald R. (eds.). Montgomery C. Meigs and the Building of the Nation's Capital. Athens, Ohio: United States Capitol Historical Society/Ohio University Press. p. 34. ISBN 9780821413975.
- Ways, Harry C. (1996). The Washington Aqueduct: 1852-1992. Baltimore, MD: U.S. Army Corps of Engineers, Baltimore District.
- Scott, Pamela (2007). "Chapter 5. The Expanding City, 1915-50". Capital Engineers: The U.S. Army Corps of Engineers in the Development of Washington, D.C., 1790-2004. Washington, D.C.: U.S. Army Corps of Engineers. pp. 204–205. ISBN 978-0160795572. Publication No. EP 870-1-67. Archived from the original on 2009-07-22. Retrieved 2023-03-24.
- Horton, Barbara (2004-02-02). "Army Map Service Historic District" (PDF). Maryland Historical Trust. pp. 1–3. Archived (PDF) from the original on 2017-02-03. Retrieved 2019-10-15.
- "Water Treatment Residuals Management Project". Washington Aqueduct. USACE. Retrieved 2023-03-30.
- "Fact Sheet: NPDES Permit No. DC0000019" (PDF). Philadelphia, PA: U.S. Environmental Protection Agency. 2021-04-13.
- "Washington Aqueduct". Baltimore, MD: U.S. Army Corps of Engineers.
- "NOAA Online Weather Data – NWS Baltimore". National Weather Service. Retrieved February 20, 2023.
- "U.S. Climate Normals Quick Access – Station: Dalecarlia RSVR, MD". National Oceanic and Atmospheric Administration. Retrieved February 20, 2023.