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Hydrograph River at a Glance Download
Potomac River at Williamsport Stage (ft)Highest Observation: 1.7 ft at 7:34AM Oct 28, 2014Highest Observation: 1.7 ft at 7:40AM Oct 29, 2014National Weather ServiceWLLM2(plotting HGIRZ) Graph Created (2:07PM Oct 30, 2014)ObservedLatest observed value: 1.7 ft at 7:40 AM EDT 29-Oct-2014. Flood Stage is 23 ft
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Datum: Not Available
NOTE: Gauge readings received once daily during low-water and more frequently during high water.

NOTE: Forecasts for the Potomac River at Williamsport are issued as needed during times of high water, but are not routinely available.

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Upstream Gauge - at Hancock Upstream Gauge Downstream Gauge Downstream Gauge - at Harpers Ferry
Flood Categories (in feet)
Major Flood Stage:28
Moderate Flood Stage:25
Flood Stage:23
Action Stage:15

Historical Crests
(1) 48.60 ft on 03/18/1936
(2) 37.00 ft on 04/27/1937
(3) 36.30 ft on 11/06/1985
(4) 36.10 ft on 10/16/1942
(5) 34.80 ft on 01/20/1996
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(P): Preliminary values subject to further review.

Low Water Records
Zoom Level:13
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Gauge LocationGauge Map Marker
Latitude/Longitude Disclaimer: The gauge location shown in the above map is the approximate location based on the latitude/longitude coordinates provided to the NWS by the gauge owner.
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62 water begins to flood the R.C. Wilson Water Treatment Plant.
29 water begins to inundate the C&O Canal Towpath.
23 water begins to inundate the Potomac Fish & Game Club.
20 water begins to inundate the Isaak Walton summer resourt community.
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Latitude: 39.609167° N, Longitude: 77.847500° W, Horizontal Datum: NAD83/WGS84

River Stage
Reference Frame
Gauge Height Flood Stage Uses
NWS stage 0 ft 23 ft Interpreting hydrographs and NWS watch, warnings, and forecasts, and inundation maps
Vertical Datum Elevation
(gauge height = 0)
(gauge height = flood stage)
Elevation information source
NAVD88 Not Available Not Available Survey grade GPS equipment, FEMA flood plain maps, newer USGS topographic maps
NGVD 29 327.7 ft 350.7 ft Older USGS topographic maps, NGVD29 benchmarks
MSL Not Available Not Available Older USGS topographic maps, MSL benchmarks
Other Not Available Not Available  

Current/Historical Observations:

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NWS Information
National Weather Service
(Baltimore/Washington) Sterling Weather Forecast Office
43858 Weather Service Rd.
Sterling, VA 20166
(703) 996-2200
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Page last modified: 5-Aug-2014 6:39 PM
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