Data Collection at U'S' Geological Survey Stream Gages

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Data Collection at U.S. Geological Survey Stream
Gages
Antietam Creek nr Sharpsburg, Md.
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The first USGS gaging station was established on
the Rio Grande near Embudo, New Mexico in 1889.
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Embudo trainees dispersed to collect data in
other locations
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Streamflow Measurements in the East
1889
1994
Flood Crest March 18, 1936
Potomac River at Chain Bridge nr Washington, D.C.
Potomac River at Point of Rocks, Md.
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The Embudo LegacyData collected using nationally
consistent, prescribed standards
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The U.S. Geological Survey currently collects
streamflow data at over 7,000 sites
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Minebank Run at Loch Raven, Md.
Potomac River at Little Falls nr Washington, D.C.
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Data from over 18,500 locations can be analyzed
with confidence
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The basic piece of data collected at gaging
stations is stream STAGE (water level)
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Stage can be sensed usingSTILLING WELLS
Intakes
Outside reference gages
Little Patuxent River nr Guilford, Md.
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Stage can also be sensed using PRESSURE
TRANSDUCERS
Gwynns Falls at Washington Blvd. at Baltimore, Md.
Orifice Line
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Stage is usually

• Measured to an accuracy standard of
• either 0.01 ft or 0.2 percent of the effective
  stage being measured -- Office of Surface Water
  memorandum 93.07

• Recorded every 15 minutes

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Most users of streamflow information need to know
the DISCHARGE of the stream
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Discharge usually measured using the
velocity-area method
Discharge Velocity x Depth x Width
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Discharge measurements are used to develop rating
curves
Rating Curve
Discharge Measurements
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Discharge must be measured at all stages
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Discharge measurements during high stages are
particularly important
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To maintain ratings, discharge must be measured
regularly
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For example rating changes as channel fills.
Stage (ft)
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1
1
10
100
1000
10000
Discharge (cfs)
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Datum must be checked regularly
Gage houses settle
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All gaging station data are checked and reviewed
regularly
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Data from USGS gaging stations can be used to
meet a variety of needs
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Current needs
Chesapeake Bay inflow Susquehanna River at
Conowingo, Md.
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Long-term needs
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Uses of Streamflow InformationFlood Frequency
Analysis
Rank Year Peak 1 1993 10,500 cfs
2 1995 3,200 3 1988 2,340 4 1989 1,850
5 1997 1,230 6 1990 948 7 1992 550
8 1996 320 9 1991 200 10 1994 163
100-year flood
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Data dissemination
http//water.usgs.gov http//md.usgs.gov
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Data dissemination
GOES
DOMSAT
Hydrologic Stations
User Operations
Wallops, Virginia Command and Data Acquisition
Center
( Internet )
Stage
http//water.usgs.gov
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USGS continues to pursue use of new technology