Frequently Asked Questions
Below is a list of common questions from StreamStats users. If you have any further question, please contact us.
How is the information from StreamStats used?
The primary products delivered by StreamStats are streamflow statistics and basin characteristics. Examples of streamflow statistics include the 100-year flood, the mean annual flow, and the 7-day, 10-year low flow. Examples of basin characteristics include the drainage area, stream slope, mean annual precipitation and percentage of forested area. Basin characteristics are the physical factors that control delivery of water to a point on a stream. This information is used to protect people and property from floods and droughts, and to manage land, water, and biological resources. StreamStats also provides descriptive information for data-collection stations, such as station name, identification number, latitude, longitude, and station type.
Engineers, land managers, biologists, and many others use streamflow statistics to help guide decisions in their everyday work. For example, engineers use streamflow statistics to map flood plains for cities and towns, and to design roads, bridges, and culverts. Scientists use streamflow statistics and basin characteristics to model the effects of changes in land use on streamflow; information that is valuable for planning purposes. Land and water-resource managers use streamflow statistics for design and management of water supplies, and for waste-water discharge permitting. Biologists use the information to determine flows needed to protect endangered aquatic animals and their habitat. Corporations use streamflow statistics to design and operate hydroelectric facilities and factories that use water or discharge waste into streams or water bodies.
How do I use StreamStats?
StreamStats has an easy-to-use interface that operates through your Web browser window. You do not need to download anything to use it. The User Instructions link on the left provides detailed instructions on use of the application and example outputs, which you should read before attempting to use StreamStats. Also, the StreamStats user interface contains a Help button in the upper right corner that give access to additional information.
How are streamflow statistics determined?
The USGS currently operates a nation-wide network of about 7,300 streamgaging stations, where streamflow is monitored continuously. Historically, the USGS also has operated more than 12,000 streamgaging stations that are not currently operational. In addition, the USGS operates thousands of partial-record stations where streamflow is measured periodically. Data collected at the continuous streamgaging stations and partial-record stations are used to calculate the streamflow statistics for the stations. These data may be accessed through the NWIS-Web database.
A process known as regionalization is used to develop equations that can be used to estimate streamflow statistics for ungaged sites. Regionalization involves use of regression analysis to relate streamflow statistics computed for a group of selected streamgaging stations (usually within a State) and basin characteristics measured for the stations. Basin characteristics measured for ungaged sites can be entered into the resulting equations to obtain estimates of the streamflow statistics.
References to reports that contain regression equations for each state are provided in a Web page that you will view when you select a state from the menu on the StreamStats State Application page. This page also contains a link to the application for the state. You should read the reports to understand how StreamStats provides estimates flows for data-collection stations and ungaged sites in the state.
How does StreamStats work?
StreamStats is a cooperative effort of the USGS and ESRI, Inc. 1 It is an integrated GIS application that uses ArcIMS , ArcSDE , ArcGIS , and the ArcHydro Tools. It incorporates a map-based user interface for site selection; a Microsoft Access database that contains information for data-collection stations; a GIS program that delineates drainage-basin boundaries and measures physical and climatic characteristics of the drainage basins; and a GIS database that contains land elevation models, historic weather data, and other data needed for measuring drainage-basin characteristics and for locating sites of interest in the user interface.
After StreamStats measures the drainage-basin characteristics, the values are input to a separate program named the USGS National Flood Frequency Program (NFF), which is a Microsoft Windows program that contains all of the USGS-developed equations for estimating flood-frequency statistics in the Nation. NFF has been modified for StreamStats so that it can also contain equations for estimating other types of streamflow statistics. All of the equations in NFF are documented through links to each individual State from the NFF web site. Output from NFF and from the Access database is presented to StreamStats users in a pop-up window on their computer desktop.
What streamflow statistics and basin characteristics does StreamStats provide?
The information provided varies by State, as programming for each State is separate in StreamStats. This allows the application to be customized for the needs of individual States. All streamflow statistics and basin characteristics provided for USGS data-collection stations were published previously in reports or on the Web, and a reference is provided for each piece of information. The database contains nearly 500 different streamflow statistics, but only a small number of them will commonly be available for individual stations. Go to the Definitions page to view a table showing the types of streamflow statistics that may be available and their definitions. The basin characteristics that are provided for ungaged sites usually are limited to those that are used in the regression equations that are available for the hydrologic region in which the site is located, as most States have been subdivided into hydrologic regions that have similar climate and physical characteristics.
What if StreamStats is not operational for my State?
The State Application link provides a map and explanation indicating implementation progress. If your State is not highlighted on the map and you are interested in making StreamStats operational there, contact the USGS Water Science Center Director for your State.
