(21 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 5-60 minute intervals and transmitted to the NWIS database every 1-4 hours.
Real-time data are available online for 31 days.
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(34 sites)
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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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(32 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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(5,038 sites)
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Data from field and/or laboratory analyses of water samples,
biological tissue, stream sediments, or other environmental samples.
Data include approved, quality-assured data that may be published,
and more recent provisional data, whose accuracy has not been verified.
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Introduction
The USGS collects and analyzes chemical, physical,
and biological properties of water, sediment and tissue samples from
across the Nation. The NWISWeb discrete
sample data base is a compilation of over 3.5 million historical
water quality analyses in the USGS district data bases through
September 2001. The discrete sample data is a large and complex set of
data that has been collected by a variety of projects ranging from
national programs to studies in small watersheds. Users should review
the help notes and particularly the
Data
retrieval precautions before beginning any retrieval or analysis of
data from this data set. Additions of more current data, modifications
to ancillary information, and enhanced retrieval options to help users
find and appropriately use the data they need are planned for a future
release of NWISWeb.
At selected surface-water and ground-water sites, the
USGS maintains instruments that continuously record physical and
chemical characteristics of the water including pH, specific
conductance, temperature, dissolved oxygen, and percent
dissolved-oxygen saturation. Supporting data such as air temperature
and barometric pressure are also available at some sites. At sites
where this information is transmitted automatically, data are available
from the real-time data
system.
You may find additional water-quality data of
interest in EPA
STORET.
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Tutorial explaining how to perform water quality retrievals and understand the results of real-time data and discrete water-quality measurements.
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