StreamStats: Map-based Web Application to Obtain Flow Data at Ungaged Streams

The United States Geological Survey (USGS) has been involved with the collection and dissemination of streamflow data for over 100 years to help communities and agencies plan, manage, and protect water resources. Most people are familiar with and have used the USGS Office of Surface Water web site (http://water.usgs.gov/osw/) to obtain a wide-range of streamflow and sediment data, water-related publications, and software produced and developed by the agency.

The magnitude, frequency, and duration of flows are often needed by hydrologists, engineers, and water-resource managers for a variety of purposes such as the design of infrastructure in and near streams, delineation and management of flood-hazard areas, channel and habitat restoration, instream-flow quantification, water rights, and water-supply planning. For each State and some Territories of the United States , the USGS has developed equations for predicting the magnitude and frequency of flood peak discharges at ungaged streams based on basin attributes. For a few States, the USGS has also developed equations for predicting flow duration exceedence discharges. To develop these predictive equations for ungaged streams, multiple-regression analyses are performed on specific streamflow statistics and basin characteristics from gaged streams. The techniques and analyses used to develop the predictive discharge equations for ungaged streams along with the reliability and limitations of the equations can be found in USGS Water Resources-Investigations Reports published for each State. In 1994, the USGS released the National Flood Frequency program (NFF) that compiled all the predictive discharge equations from each State, making it relatively easy for someone to estimate the discharge for different recurrence intervals on an ungaged stream based on the input of basin characteristics for the site (Reis and Crouse, 2002). NFF version 3.2 was released in December 2004. See the April 2003 issue of Stream Notes for a more detailed discussion of the NFF program.

Although the NFF software makes it easier to predict discharge magnitudes for different recurrence intervals for ungaged streams, anyone who has measured basin characteristics from maps for data input into the equations is well aware that this process can be tedious and time-consuming. The USGS is currently developing StreamStats, a map-based Web application (figure 1) that has automated the measurement of basin characteristics using Geographic Information System (GIS) programs, which then interfaces with the NFF program to estimate streamflow statistics for the site. Determining basin characteristics for ungaged streams using StreamStats is a more accurate, more consistent, and faster process than previously used manual methods, giving the user more confidence in the accuracy of the streamflow statistics produced from the inputted drainage basin data.

StreamStats Availability and Documentation

The StreamStats application is currently available in three States ( Idaho , Vermont , and Washington) with a fourth State ( Pennsylvania ) soon to be available after internal testing is completed (figure 2). Numerous other States are in the process of developing the StreamStats application. Information about StreamStats is available from the USGS Web site at http://water.usgs.gov/osw/streamstats/index.html. This web site provides links to documents describing the applications and limitations of StreamStats, documents describing the software and databases used to develop the StreamStats application, instructions for using StreamStats, presentations given by the developers of StreamStats, and those States where StreamStats is currently available. At the web page for individual States with the StreamStats application, there are links to the USGS Water-Resources Investigation Reports that describe the techniques and analyses used to develop the predictive discharge equations for ungaged streams and the reliability and limitations of the equations. The USGS StreamStats Fact Sheet (Reis et al., 2004) provides an excellent overview and description of the StreamStats application.

StreamStats Features

StreamStats is a map-based Web application that does not require any special software other than a Web-browser commonly found on most computers. Internet Explorer 5.0 or higher is the recommended browser to use for StreamStats. A high-speed internet connection is recommended as the StreamStats application interfaces with multiple GIS programs and databases to generate drainage basin data and the NFF software to calculate streamflow statistics. The StreamStats application has four primary components:

1) A user interface that displays maps at different scales allowing users to navigate and select ungaged stream locations or USGS gaged stream locations where streamflow statistics and data are needed,

2) An automated GIS process that determines drainage basin boundaries at the user-selected ungaged stream,

3) An automated GIS process that measures drainage basin characteristics needed to calculate streamflow statistics at the user-selected ungaged stream, and

4) An automated process that takes the measured drainage basin characteristics for the user-selected ungaged stream and calculates the equations used to predict the various streamflow statistics.

The StreamStats map-based interface (figure 1) allows the user to navigate to areas of the map by 1) zooming in and out to locate the site of interest at different scales, or 2) zooming to a named place, named water feature, or a specified latitude and longitude using the “Zoom To” pull down menu. The Map Layers Frame allows users to display features such as roads, highways, 7.5 minute quadrangle boundaries, water bodies, county boundaries, cities, hydrological unit code (HUC) boundaries, and gage stations. Topographic and physical features displayed on the map are scale dependent making it relatively easy to navigate to different areas on the map and to select gaged and ungaged site locations of interest (figure 3). The various buttons at the top of the Map Frame allow users to query information on features for selected map layers, delineate drainage basin boundaries for ungaged streams, edit the boundaries of the delineated basin, obtain streamflow statistics for the delineated ungaged stream, obtain drainage basin characteristic data for the delineated ungaged stream, retrieve USGS stream gage data and information from the National Water Information System (NWIS), download Environmental Systems Research Institute, Inc. (ESRI) shape files, and print the displayed map.

One of the many excellent features of StreamStats is its ability to plot active and inactive USGS gage stations, making it easier for users to identify the location of gage stations in a given area. The gage stations displayed on the map are linked to the USGS database containing streamflow data, streamflow statistics, and site information. The user simply needs to click on the “NWIS” button followed by a click on the USGS gage station of interest to directly link to the NWIS database storing the streamflow data, streamflow statistics, and site information for the station.

The type of drainage basin data needed for using the equations to predict streamflow statistics varies from State to State (table 1). Some of the drainage basin parameters are quite time intensive to collect and potentially inaccurately determined because of the user's inexperience and/or ability to collect the measurements. The ability of StreamStats to determine multiple drainage basin data in tens of seconds from a user selected location is impressive. Moreover, it provides a more accurate and consistent process for determining the necessary drainage basin variables.

To obtain the drainage basin data, the user needs to be zoomed into a scale less than 1:24,000 or the “BasinDelineation” button will not be activated. After clicking on the “BasinDelineation” button and clicking on the point in the stream to be measured, the StreamStats application delineates the drainage basin boundary (figure 4). A pop-up window warns the user to check the delineated drainage basin for accuracy before the clicking on the “FlowStats” or “BasinChar” buttons. The StreamStats application allows the user to edit the delineated basin so that is more accurately delineated. Simply click on the “EditBasin” button and remove or add areas to the existing delineated drainage basin boundary.

When the “FlowStats” button is clicked, the StreamStats application determines the drainage basin characteristics needed as input into the equations for predicting streamflow statistics. The drainage basin data are then automatically loaded into the NFF program that interfaces with StreamStats to calculate the streamflow statistics for the ungaged stream. The estimated streamflow statistics, standard errors associated with the streamflow statistics, drainage basin characteristics, and the range of values for a given drainage basin variable used to develop the predictive equations for the selected site will appear in a pop-up Web Browser window (figure 5).

For the most part, the StreamStats application is quite impressive and easy to use, but there are a couple of items that would improve the application. First, the Map Frame window is small and cannot be expanded in the Internet Explorer Web-browser to display more of the map. This makes navigating the map to specific locations at small scales somewhat difficult. Second, the Map Frame does not allow the user to manually select the map scale, instead, map scale is determined to the degree to which the user zooms in or zooms out of the map. Third, edits made to the original drainage basin boundary are not saved preventing the user from reviewing their changes.

With these minor criticisms aside, StreamStats is a powerful and excellent tool for those needing streamflow statistics at ungaged streams and for spatially identifying USGS gage stations in an area. Those working in Idaho , Vermont , and Washington are fortunate to have such a tool at their disposal.

References

Ries III, K.G., Steeves, P.A., Coles, J.D., Rea, A.H., and Stewart, D.W., 2004, StreamStats: A U.S. Geological Survey Web Application for Stream Information, U.S. Geological Survey Fact Sheet FS 2004-3115, 4 p.

Ries III, K.G. and Crouse, M.Y., 2002, The National Flood Frequency Program, version 3.2: A computer program for estimating magnitude and frequency of floods for ungaged sites, U.S. Geological Survey Water-Resources Investigations Report 02-4168, 42 p.

Figure 1. A screen shot of the StreamStats map-based interface for Washington . The star symbol identifies the location of the Stevens Creek watershed, Olympic National Forest, WA.

Figure 2. Map of states were StreamStats is fully operational, soon to be released after internal testing, or being developed.

Figure 3. Screen shot showing more detailed topographic and physical features as one zooms in on the area of interest. The Stevens Creek watershed on the Olympic National Forest, WA has been outlined to better highlight its location. USGS gage station locations in the area are identified by darkened triangles.

Table 1. A list of drainage basin characteristics used to calculate streamflow statistics in Idaho , Vermont , and Washington .

Figure 4. Screen shot showing the delineated drainage basin boundary of Stevens Creek on the Olympic National Forest, WA. The Stevens Creek drainage basin has been outlined to better highlight its location.

Figure 5. Screen shot showing the streamflow statistics report for Stevens Creek , Olympic National Forest, WA.