(9,332 sites)
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Real-time data are time-series (recorded at fixed intervals) data from automated equipment and represent
the most current hydrologic conditions. Measurements are commonly recorded
at 15- to 60-minute intervals and transmitted to the NWIS database every 1-4 hours.
Real-time data are available online for 120 days.
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(25,823 sites) |
Daily values are summarized from time-series
data for each day for the period of record and may represent the daily
mean, median, maximum, minimum, and/or other derived value. Daily values include
approved, quality-assured data that may be published, and more recent
provisional data, whose accuracy has not been verified.
Example.
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(24,326 sites)
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Statistics are computed from approved daily mean time-series data at each site.
These links provide summaries of approved historical daily values for daily,
monthly, and annual (water year or calendar year) time periods.
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(27,964 sites)
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Annual maximum instantaneous peak streamflow and gage height
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(52,551 sites) |
Periodic manual measurements of streamflow and gage height. These measurements
are often used to supplement and (or) verify the accuracy of the time-series measurements.
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Introduction
Nationally, USGS surface-water data includes more than 850,000 station
years of time-series data that describe stream levels, streamflow
(discharge), reservoir and lake levels, surface-water quality, and
rainfall. The data are collected by automatic recorders and manual measurements at field installations across
the Nation.
Data are collected by field personnel or relayed through telephones or
satellites to offices where it is stored and processed. The data
relayed through the Geostationary Operational Environmental Satellite
(GOES) system are processed automatically in near real time, and in
many cases, real-time data are available
online within minutes.
Once a complete day of readings are received from a site, daily
summary data are generated and stored in the data base. Recent provisional daily data are updated on the
web once a day when the computation is completed.
Annually, the USGS finalizes and publishes the daily data in a series
of water-data reports. Daily streamflow
data and peak data are updated
annually following publication of the reports.
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Tutorial explaining how to perform a surface water retrieval and understand the results
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