A valuable water resources web resource
(Note: All text excerpted with permission from USGS Fact Sheet FS 2008-3067 by Kernell G. Reis III, John D. Guthrie, Alan H. Rea, Peter A. Steeves, and David W. Stewart. The full StreamStats overview is available online at http://pubs.usgs.gov/fs/2008/3067/ )
Streamflow statistics, such as the 1-percent flood, the mean flow, and the 7-day 10-year low flow, are used by engineers, land managers, biologists, and many others to help guide decisions in their everyday work. For example, estimates of the 1-percent flood (the flow that is exceeded, on average, once in 100 years and has a 1-percent chance of being exceeded in any year, sometimes referred to as the 100-year flood) are used to create flood-plain maps that form the basis for setting insurance rates and land-use zoning. This and other streamflow statistics also are used for dam, bridge, and culvert design; water-supply planning and management; water-use appropriations and permitting; wastewater and industrial discharge permitting; hydropower facility design and regulation; and the setting of minimum required streamflows to protect freshwater ecosystems.
Streamflow statistics could be needed at any location along a stream. At U.S. Geological Survey (USGS) streamflow data-collection stations, which include streamgaging stations, partial-record stations, and miscellaneous-measurement stations, streamflow statistics can be computed from available data for the stations. Streamflow data are collected continuously at streamgaging stations. Streamflow measurements are collected systematically over a period of years at partial-record stations to estimate peak-flow or low-flow statistics. Streamflow measurements usually are collected at miscellaneous-measurement stations for specific hydrologic studies with various objectives.
StreamStats is a Web-based Geographic Information System (GIS) application that was created by the USGS, in cooperation with Environmental Systems Research Institute, Inc. (ESRI), to provide users with access to an assortment of analytical tools that are useful for water-resources planning and management. StreamStats allows users to easily obtain streamflow statistics, basin characteristics, and descriptive information for USGS data-collection stations and user-selected ungaged sites. It also allows users to identify stream reaches that are upstream and downstream from user-selected sites, and to identify and obtain information for locations along the streams where activities that may affect streamflow conditions are occurring. This functionality can be accessed through a map-based user interface that appears in the user’s Web browser, or individual functions can be requested remotely as Web services by other Web or desktop computer applications. StreamStats can perform these analyses much faster than historically used manual techniques.
|Figure 1. Example of the StreamStats map viewer page for a portion of the upper Big Thompson watershed, Black Canyon Creek near Estes Park, Colorado.|
The StreamStats home page is at http://streamstats.usgs.gov. This page provides a brief description of the application. A gray box to the left of the page provides links to other pages that document and provide access to the application. The State Applications link is used to access the individual state applications. It presents a map of the United States with individual states shown in different colors depending on their implementation status. Users can access an introductory page for an individual state by selecting the state from a scroll list at the top of the page, or by selecting an implemented state shown as green or purple on the map.
The StreamStats user interface allows users to locate, select, and obtain information for gaged and ungaged sites of interest. The largest part of the interface consists of the Map Frame, which displays default and selected digital map layers. The Console, to the left of the map, allows control of the display of map layers and map navigation, and provides information about the map. The Toolbar above the map frame contains a series of buttons (tools) that are used to change the scale (zooming in and out) and the center (panning) of the map, and that allow users to initiate the various StreamStats functions.
StreamStats provides convenient access to descriptive information, basin characteristics, and streamflow statistics for USGS data-collection stations. Users can zoom in to the location of a data-collection station in the user interface, click on the Gaging Station Information button, and then click on the station symbol to obtain a report that contains available information for the station. A national application that is accessible through the USGS Station Statistics Web page provides access to this functionality for data-collection stations in all states. Similar functionality also is available in the applications for each implemented state.
Descriptive information provided in the StreamStats output for the data-collection stations includes: the USGS station identification number, station name, station type, period of record, latitude, longitude, hydrologic unit code (HUC), major drainage basin name, county, U.S. Census Bureau Minor Civil Division (MCD) name, directions to locate the station, and remarks indicating any effects of human impacts or other pertinent information about the stations. Only previously published basin characteristics and streamflow statistics are available from StreamStats. Content varies among stations depending on station type and the interests of local cooperators who may have shared in the cost of computing the statistics. The outputs contain citations to the original source reports that explain the methods used to determine the information.
StreamStats can estimate streamflow statistics for ungaged sites either on the basis of regional regression equations or on the basis of the known flows for nearby stream.gaging stations. Estimates of streamflow statistics that are obtained from regression equations are based on the assumption of natural flow conditions at the ungaged site. If human activities such as dam regulation and water withdrawals substantially affect the timing, magnitude, or duration of flows at a selected site, the regression-equation estimates provided by StreamStats should be adjusted by the user to account for those activities.
The StreamStats web application is fully functional for Colorado and is accessible at: http://water.usgs.gov/osw/streamstats/colorado.html
Thank you to Cory Stephens, USGS Colorado Water Science Center, for contributions to this article.