Information for USGS streamgages can be obtained by clicking or tapping on a triangular streamgage symbol in the Map Frame. The streamgage symbols will not appear on the map until it is zoomed into at least zoom level 9. The map legend indicates the meanings of the various colors.
After selecting a streamgage, a white dialog box will appear above the streamgage symbol, which lists the latitude and longitude of the location, the USGS station identification number, the station name, a link to the NWIS page for the station, a link to the StreamStats page for the station, and the drainage area for the station. Clicking on one of the links in the dialog box will cause the respective page to open in a separate window. The NWIS page for the station provides access to all instantaneous and time-series data that are available for the station. The StreamStats page provides access to descriptive information as well as previously published basin characteristics and streamflow statistics for the station. A description of the StreamStats streamgage output is described in The Reports for Streamgages section of this manual.
Reports for streamgages have header at the top, which identifies the station number and name, and provides a link to the NWIS-Web page for the station, from which users can obtain time-series data for the station. The header is followed by four tables that include (1) descriptive information, (2) basin characteristics, (3) streamflow statistics, and (4) citations. The information that is available for individual streamgages varies widely depending on the type and currency of the data collected there, and on the interests of the other agencies that cooperate with the USGS to maintain the streamgages.
Information provided in this table may include:
Station type: Indicates the type of record collected at the station. Possible types are: continuous-record streamgage, low-flow partial-record station, peak-flow partial-record station, peak- and low-flow partial-record station, miscellaneous-measurement station, peak-flow partial record and stage-only, continuous-record stage-only, and undefined.
Location: Describes the location of the station.
Gage: Describes the installed instrumentation and the gage datum.
Regulation and Diversions: Describes any human manipulation of streamflow at the station.
Regulated?: Indicates if streamflow at the station is affected by flow regulations or diversions. Possible values are True, False, or Unknown
Period of Record: Indicates the starting and ending years of data collection
Remarks: Provides description of any factors that affect the flow conditions at the station.
Latitude: Latitude of the station location, in decimal degrees, NAD83
Longitude: Longitude of the station location, in decimal degrees, NAD83
Hydrologic unit code: The 8-digit hydrologic cataloging-unit number assigned to the drainage basin in which the station is located. Additional information can be obtained at https://water.usgs.gov/nawqa/sparrow/wrr97/geograp/geograp.html
County: The name of the county in which the station is located
HCDN2009: Yes or No field that indicates if the station is included HCDN2009 dataset, which is composed of stations that were screened to exclude sites where human activities, such as artificial diversions, storage, and dam regulations affect the natural flow of the watercourse
These tables may contain any of potentially hundreds of physical and climatic characteristics of the drainage basin that contributes streamflow to a data-collection station. The characteristics that are available vary widely among the stations. The table is separated into sections of characteristics of the same type. The types may include precipitation, temperature, climate, runoff, flood depth, recharge, topographical, soil, geological, stream channel, basin dimensional, and burned area characteristics, as well as additional descriptive information. The table consists of four columns:
- Characteristic Name - the short names of the characteristics. Definitions of the characteristics are provided on the Basin Characteristics Definitions page.
- Value - the quantity of the characteristic that was measured for the station
- Units - the English units of measure for the value
- Citation Number - number that corresponds with the Citation Number in the Citations table. Each physical characteristic and streamflow statistic that is provided by StreamStats has been published previously in a report that is cited in the Citations table and is referenced by the Citation Number in the other tables.
These tables may contain any of more than 2,500 different streamflow statistics separated into as many as 41 sections of statistics of the same type, such as peak-flow statistics, low-flow statistics, and flow-duration statistics. The tables include 13 columns, although usually at least some of them will not be filled:
- Statistic Name - gives the names of the statistics. Within the table, the statistics are grouped by statistic type.
- Value - gives the computed value for the corresponding statistic
- Units - gives the English units of measure for the value
- Citation Number - gives a number that corresponds with the Citation Number in the Citations table
- Preferred? – indicates Y if the statistic is the preferred value, and N if it is not preferred
- Years of Record – the number of years of record that were used to compute the statistic
- Standard Error, percent – the standard error, in percent, of the computed statistic, which indicates there is an approximately 2/3 chance that the true value is within the given percentage of the provided value
- Variance, log-10 – the variance of the estimate, as computed from the base-10 logarithms of the data that were used to compute the statistic
- Lower 95% Confidence Interval – the lower end of the interval within which there is a 95 percent chance that the true value of the statistic occurs
- Upper 95% Confidence Interval – the upper end of the interval within which there is a 95 percent chance that the true value of the statistic occurs
- Start Date –the beginning date of the period of record that was used to compute the statistic
- End Date - the ending date of the period of record that was used to compute the statistic
- Remarks – optional comments about how the statistic was computed
Typically, when a new value of a statistic is published for a station, and the new value was computed using a longer record or improved methods, or both, then the new value is considered to supersede the older value. As a result, normally when new values of a statistic become available they replace the older values in the database that stores the statistics for StreamStats. However, StreamStats can provide multiple values of the same statistic in cases where there is justification to do so. An example is where a state has regulations that require the use of statistics from a specific report, but newer values have become available since the report was published. In such cases, IsPreferred? will be set to Y for the newer value and to N for the older value, and both values will appear in the statistics table.
Unless otherwise noted, all streamflow statistics presented in the output tables, except low-flow frequency statistics, were computed on the basis of water years, which begin October 1 of the preceding year and end September 30 of the given year. Low-flow frequency statistics, such as the 7-day, 10-year low flow, were computed on the basis of climatic years, which begin on April 1 of the given year and end on March 31 of the following year. Statistics that were computed using data from nonstandard time periods or periods of less than a year will indicate those time periods in their names and definitions.
Definitions for the streamflow statistics are provided on the Streamflow Statistics Definitions page.
NOTE: The information that StreamStats provides in reports for data-collection stations is maintained in a database that must be updated by scientists who work in the USGS state offices. These offices generally rely on partnering with local agencies to cover at least half of the cost of the needed database work. Often, the database is updated as part of the process of initially implementing StreamStats, but additional updates subsequent to implementation and updates for states that are not implemented sometimes are difficult to achieve. As a result, some of the data in our database is out of date.
If a statistic found in a StreamStats output has a citation that is from an older source than the reports listed on the State/Regional Info tab for an implemented state, then the newer source should be examined to determine if a newer statistic is available for the station. A more comprehensive list of reports that contain regression equations and computed interpretive streamflow statistics for the streamgages used to develop the equations is at https://water.usgs.gov/osw/programs/nss/NSSpubs_Rural.html. Also, the USGS office for each state maintains a web page at http://xx.water.usgs.gov, where xx is the 2-letter postal cost for the state. The web pages normally provide links to publications that have produced by scientists in that state. A search of these publications may turn up additional reports that contain streamflow statistics.
These tables contain columns of the citation numbers given in the previous tables, the corresponding citations for the reports that contain the statistics, and links to the online versions of the reports, respectively. Users can refer to those reports to determine when, why, and how the statistics were calculated.
Many of the statistics presented in the tables have an associated citation of “Imported from Basin Characteristics file.” The Basin Characteristics File (BCF) was a USGS database that was retired in the late 1990s. No time tags were associated with any of the data entered in the BCF. As a result, users should understand that information from the BCF is likely to be 20 or more years old. In many cases, newer information is available in reports published by the various USGS Water Science Centers. Users should check the Web pages of the individual Centers to determine if reports containing newer statistics are available.