Assessing the National Streamflow Information Program (2004) / Chapter Skim
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5 Streamflow Information
5 Streamflow Information
Pages 100-119
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From page 100... ...
a program for intensive data collection in response to major floods and droughts; 2. a program for periodic assessments and interpretation of streamflow data to better define their statistical characteristics and trends; 3.
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From page 101... ...
Changes in the geomorphology of river channels, such as river-bank erosion location and processes, and sedimentation volumes and distribution would be documented for high- as well as low-flow conditions." Intense Monitoring During Floods Streamflow conditions during floods are materially different from those during normal or low flows because the stream is no longer confined within its channel and may range widely over the floodplain (Figure 5-1)
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From page 102... ...
In particular, some of the findings challenge conventional wisdom on the role of major floods in the transport of agricultural chemicals from the landscape (Goolsby et al., 1993)
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From page 103... ...
It may even be possible to routinely monitor regional floods from unmanned aerial vehicles similar to the drones employed during military campaigns. Since the extent and depth of flood inundation are the critical factors causing flood damage, remotely sensed images of flood inundation from space, coupled with an accurate terrain surface model, would allow computation of the volume of water inundation.
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From page 104... ...
A tertiary site is one where no stage record is maintained, but rather the site is used solely for periodic streamflow measurement by current meters, acoustic Doppler current profilers, or perhaps in the future by noncontact landbased remote sensing approaches (see "Methods Development and Research")
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Plans for intensive data collection during major flood and drought events should be designed both to test scientific hypotheses on river processes, and to support regional analysis and estimation of streamflow information at ungaged sites.
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From page 106... ...
However, there are significant opportunities for integrating ancillary information in the study of regional flow processes. For example, the use of climate and weather data resources, as well as geographical information, can be integrated with streamflow information to examine and account for the effects of changing climate, land use, and other variables on regional flow statistics and flood frequencies.
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Such trends may be an indicator of the impact of climate change on water resources or the effects of human changes to the landscape. Using a subset of 395 streamgage records for the Hydroclimatic Data Network (HCDN)
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From page 108... ...
For instance, large-scale climate anomalies, such as the El Niño-Southern Oscillation and the Pacific Decadal Oscillation, are now known to affect streamflow variations over interannual to interdecadal time scales (e.g., Kahya and Dracup, 1993; Redmond and Koch, 1991; Sankarasubramanian and Lall, 2003)
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From page 109... ...
system. For each gage and for each calendar day, the USGS has analyzed historical streamflow records to generate a percentage distribution of flow expected, and the actual flow is measured against these values to determine whether flow is above, below, or within normal flow conditions.
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Regression equations were then developed, and these equations were used to convert the real-time sensed variables into estimates with error bars of derived water quality variables.
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From page 111... ...
Streamstats In a pilot study initiated by the USGS Massachusetts District, a system called Streamstats has been developed to allow estimation of streamflow characteristics (mean, median, percentile values of the frequency distribution) at ungaged locations as a function of basin characteristics and regression equations (http://ststdmamrl.er.usgs.gov/streamstats/)
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. Streamflow Information Products Two traditional roles of the USGS have been the measurement and publication of historical daily mean streamflow data and streamflow statistics.
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FIGURE 5-5 Streamflow information products and locations at which they are available. Filled circles represent the current capability, with the size of the circle representing the availability of data.
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of the U.S. Army Corps of Engineers, which has created a Corps Water Management System that ingests real-time rainfall and streamflow information and computes flows, water surface elevations, and flood maps using HEC models embedded in the system.
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Promising techniques include Doppler radar and visible imagery techniques for surface velocity measurement and ground penetrating radar (GPR) and light detection and ranging (lidar)
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A suspended Mala Geoscience GPR measured water depths, and the University of Washington X-band Doppler radar measured surface velocities from the river's bank. Depth-averaged velocities were estimated by multiplying the surface velocity by 0.85 (assuming a parabolic velocity profile)
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From page 117... ...
Still, the committee also envisions tailoring techniques to unique applications, such as those required to make intensive measurements at ungaged sites during floods and droughts. These other applications might use technologies such as video image analysis for discharge estimation or handheld radar guns for spot measurement of surface velocities, increased use of lidar for floodplain mapping or enhanced forms of lidar that can penetrate water for mapping stream bathymetry, and the remote sensing of water surfaces and areas of flow inundation using land-, aircraft-, or spacebased sensors.
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From page 118... ...
With due care in ensuring comparability between traditional streamgaging data and new technologies, the USGS is encouraged to continue aggressively pursuing these technologies for measurement of streamflow and related parameters with a view to accelerating the implementation of time- and labor-saving flow measurement techniques, and continuous water quality monitoring, as soon as practicable. SUMMARY In general, the four other components of the NSIP that complement the streamgaging network -- intensive data collection during major floods
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From page 119... ...
This information should be integrated with ancillary data such as soil moisture and CO2 flux data as appropriate. Plans for intensive data collection during major floods and drought events should be designed both to test scientific hypotheses on river processes, and to support regional analysis and estimation of streamflow information at ungaged sites.
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