Application Description
StreamStats is a Web-based Geographic Information Systems (GIS) application that provides users with access to an assortment of analytical tools that are useful for a variety of water-resources planning and management purposes, and for engineering and design purposes. StreamStats users can select USGS data-collection station locations shown on a map and obtain previously published information for the stations. Users also can select any location along a stream and obtain the drainage-basin boundary, basin characteristics, and estimates of streamflow statistics for the location. The streamflow statistics that StreamStats can provide for data-collection stations and for user-selected ungaged sites vary among the implemented states and among data-collection stations within states. Estimates obtained for ungaged sites assume natural flow conditions at the site.
The StreamStats version 4 application is currently in BETA. Absolutely no accuracy or completeness guarantee is implied or intended. The U.S. Geological Survey expressly disclaims responsibility for damages or liability that may arise from use of these data.
StreamStats functionality is based partly on the ArcHydro Data Model and Tools and partly on Python scripts, and is implemented using ArcGIS Server technology. It incorporates a map-based user interface for site selection; a relational database that contains information for data-collection stations; a GIS program that delineates drainage basins and measures basin characteristics; and a GIS database that contains digital representations of the land surface (digital elevation models and derivative products), historic climate data, and other data needed for locating sites of interest in the user interface, delineating drainage basins, measuring drainage-basin characteristics, and searching upstream and downstream along streams from selected sites to identify activities that may affect streamflow or water quality at the sites.
The user interface can be used to zoom in by various methods to select locations where information is desired. When a USGS data-collection station is selected, information for the station appears in a pop-up window. When an ungaged site is selected, StreamStats computes the drainage-basin boundary for the site and presents it to the user in the map frame.
The information contained in the user instructions should be read before attempting to use StreamStats. Links to the version 3 and beta version 4 user instructions are to the left on this page and on other StreamStats web pages. Links to the user instructions also are provided in the user interfaces. For states that have not yet been implemented, information for USGS data-collection stations can be accessed through the beta version 4 application by clicking on the toolbox icon near the top left of the map and then on Query Streamgages button.
StreamStats determines drainage-basin boundaries by use of digital elevation data. These data usually are derived from digital elevation data from the National Elevation Dataset (NED) that have been specially processed so that the elevation data conforms to the digital stream channels depicted in the high-resolution version of the National Hydrography Dataset (NHD) and to the drainage-basin boundaries of the Watershed Boundary Dataset WBD. This processing results in drainage-basin boundary delineations that generally are superior to delineations that can be obtained directly from the NED. Still, users should be aware that use of any digital elevation data to delineate drainage boundaries can lead to errors; especially in flat areas. Users should check delineations carefully and use the EditBasin basin boundary editing tool that is provided in StreamStats to correct any errors, if necessary.
After the user indicates that the boundary is correct, StreamStats measures the drainage-basin characteristics for the site. The values are then input to a separate program named the USGS National Streamflow Statistics Program (NSS), which is a desktop program that contains all of the USGS-developed equations for estimating flood-frequency statistics in the nation, plus equations for estimating other streamflow statistics in many states. NSS estimates the streamflow statistics for the ungaged site and then StreamStats presents the statistics and the basin characteristics for the site in a pop-up Web-browser window. All of the equations in NSS are documented in reports that can be accessed through links to each individual state from the NSS Web site. The StreamStats Web site also has links to these reports on introductory pages for each state application. The introductory pages can be accessed from the State Applications link.
StreamStats provides estimates of various flow statistics for user-selected sites by solving regression equations. The equations generally were developed separately for each state through cost-sharing agreements between the USGS and state agencies. As a result, the equations that are available for a given state vary based on which statistics the state agencies need for regulatory, planning, or other purposes. The Version 3 State Applications link to the left provides a map to indicate where StreamStats has been implemented and where work is in progress. The page also provides links to introductory pages for each application that describe the available functionality and any special issues with using the state application, provide links to related reports, and identify cooperating agencies. A similar map is provided in the beta version 4 user interface at start-up, and after selecting a state, the state’s introductory page can be accessed by clicking on the About link above the map and then on the State/Regional Info tab.
The regression equations were developed through a process known as regionalization. This process involves use of regression analysis to relate streamflow statistics computed for a group of selected streamgaging stations (usually within a state) to 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. Users should note that estimates provided assume natural flow conditions at the site. The StreamStats Limitations page describes additional limitations for use of the equations and StreamStats, in general.
In addition to use of regression equations to estimate streamflow statistics for ungaged sites, StreamStats is able to estimate the statistics based on the flow per unit area of statistics for an upstream or downstream gaging station. This method is documented on page 9 of a report by Ries (2006). Application of this method is limited to ungaged sites with drainage areas that are within 0.5 and 1.5 times the drainage area for an upstream or downstream gaging station. This process is explained in more depth on the Ungaged Sites page.
Several tools are in development that will rely on searching along the stream network upstream or downstream from user-selected sites to identify stream reaches and water-related activities along the streams, such as dams and point discharges, and obtain information about those activities. In addition, users will be able to obtain elevation profiles along stream channels and between points on the land surface.
