Data Collection at U.S. Geological Survey Stream Gages - PowerPoint PPT Presentation

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Data Collection at U.S. Geological Survey Stream Gages

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  1. Data Collection at U.S. Geological Survey Stream Gages Antietam Creek nr Sharpsburg, Md.

  2. The first USGS gaging station was established on the Rio Grande near Embudo, New Mexico in 1889.

  3. Embudo trainees dispersed to collect data in other locations

  4. 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.

  5. The Embudo LegacyData collected using nationally consistent, prescribed standards

  6. . The U.S. Geological Survey currently collects streamflow data at over 7,000 sites Minebank Run at Loch Raven, Md. Potomac River at Little Falls nr Washington, D.C.

  7. Data from over 18,500 locations can be analyzed with confidence

  8. The basic piece of data collected at gaging stations isstream STAGE (water level)

  9. Stage can be sensed usingSTILLING WELLS Intakes Outside reference gages Little Patuxent River nr Guilford, Md.

  10. Orifice Line Stage can also be sensed usingPRESSURE TRANSDUCERS Gwynns Falls at Washington Blvd. at Baltimore, Md. Orifice Line

  11. Basic Data Recorder 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

  12. Most users of streamflow information need to know the DISCHARGE of the stream

  13. Channel Cross Section Discharge usually measured using the velocity-area method Discharge= Velocity x Depth x Width

  14. Discharge measurements are used to develop rating curves Rating Curve Discharge Measurements

  15. Discharge must be measured at all stages

  16. Indirect measurement Discharge measurements during high stages are particularly important

  17. To maintain ratings, discharge must be measured regularly 100 For example: rating changes as channel fills. Stage (ft) 10 1 1 10 100 1000 10000 Discharge (cfs)

  18. Staff gages can be damaged Surveying crew from Utah District Benchmark at a station Datum must be checked regularly Gage houses settle

  19. By local office personnel Jack Doyle Boise Field Office And by national review teams All gaging station data are checked and reviewed regularly

  20. Data from Thomas and Wahl, 1993 Data from USGS gaging stations can be used to meet a variety of needs

  21. Modeling and flood forecasting Current needs Chesapeake Bay inflow Susquehanna River at Conowingo, Md.

  22. Regional relations Long-term needs

  23. Uses of Streamflow Information:Flood 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

  24. Data dissemination http://water.usgs.gov http://md.usgs.gov

  25. GOES DOMSAT Data dissemination Hydrologic Stations User Operations Wallops, Virginia Command and Data Acquisition Center ( Internet ) Stage http://water.usgs.gov

  26. Acoustic doppler current profiler being used in Idaho Post-mounted gage house and sattelite antenna Aquacalc being used to collect discharge information USGS continues to pursue use of new technology