Slide 1

U.S. Geological Survey streamgages provide hydrologic information needed
to define, use and manage the Nation's water resources. The following
presentation describes methods used to collect data at USGS gaging
stations. These methods, along with the underlying philosophy of the
streamgaging program have allowed the USGS to collect relevant
streamflow data for over 100 years.

Slide 2

The U.S. Geological Survey began collecting streamflow information in
1889, when the first stream-gaging station was established on the Rio
Grande River near Embudo New Mexico. Personnel from the Irrigation
Survey, which was then a branch of the U.S. Geological Survey, were
directed by John Wesley Powell to develop procedures that could be used
to produce reliable streamflow estimates. Powell felt that it was
important to inventory the flow of streams in the arid west prior to
settlement.

Slide 3

The U.S. Geological Survey currently operates over 7000 gaging stations.

Slide 4

The basic piece of data recorded at gaging stations is stream stage,
which is the height of the water surface above some datum. Stage is
referred to as \"Gage Height\" when referenced to a reading on a gage.

Slide 5

Although stream stage is directly useful for some purposes, such as
floodplain mapping, most users of streamflow information need to know
the discharge of the stream. Discharge is the volume of flow passing a
specific point in a given amount of time.

Slide 6

A continuous record of discharge is determined by developing a
relationship between stage, which is measured continuously, and
discharge. This \"rating\"is developed using data from individual
discharge measurements.

Slide 6A

Use of ratings to convert stage to discharge would be rather straight
forward except for the fact that stream channels change as they scour
and fill. For example, if sediment is deposited in the channel bottom,
as indicated here in red, discharge will be less than it was previously
for the same stage. Because most channels erode or fill naturally,
discharge must be measured regularly. These measurements document any
changes, or lack of changes, to ratings. Discharge is measured at most
gaging stations every 6 or 8 weeks. Measurements are made more
frequently at sites where the streambed is particularly unstable.

Slide 7

Streamflow information can be used to meet a variety of needs. The USGS
locates and operates gages to maximize the usefulness of data collected
at gaging stations.

Slide 8

A few of the ways streamflow data are used are summarized in the next
few slides. As shown here, streamflow data provide the basis for flood
warning and flood forecasting. Ninety-eight percent of gaging stations
used for real-time flood forecasting in the United States are operated
by the USGS.

Slide 9

Rafters used data from gaging stations to assess river conditions prior
to river trips.

Slide 10

Streamflow data tell reservoir operators how much water is entering and
leaving their resrvoirs. These data provide operators with the
information they need to efficiently manage reservoir operations. Stage
data collected in reservoirs quantify reservoir storage.

Slide 11

Streamflow data collected over a period of time are used to understand
the magnitude and frequency of flooding. This understanding forms the
basis for mapping flood hazards on floodplains. Highighway engineers
must also have some idea of the magnitude and frequency of flooding
before they can design bridges and highways.

Slide 12

Data from gaging stations are disseminated in a variety of ways. Data
are telemetered using the GOES satellite system, cellular phones, or
land lines from about 5,000 gages currenly operated by the USGS.
Telemtered data are made available in near-real time on the world wide
web. All data collected at USGS gaging stations are published on an

annual basis in paper reports, CD-ROM based reports, and on the
world-wide web.

.

Slide 13

The USGS is constantly trying to find ways to collect and analysize
better data more efficiently. For example, data from discharge
measurements can now be automatically stored and computed when
measurement are being made. Accoustic doppler technology deployed using
a variety of methods allows us to collect data more efficiently and to
collect data at places and times where it has historically been
difficult or impossible to collect.

Slide 14

The USGS will continue to build on its Embudo legacy by collecting,
analyzing, and delivering data on streamflow in our nation\'s rivers and
streams.