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The Nation depends on the U.S. Geological Survey (USGS) to provide information needed to protect people and property from floods, and to protect water quality. Streamflow statistics, such as the 100-year flood, the annual mean flow, and the 7-day 10-year low flow (7Q10), frequently are used by engineers, land managers, biologists, and many others to help guide decisions in their everyday work. Example uses of streamflow statistics are for flood-plain mapping for insurance and zoning, bridge and culvert design, setting of TMDLs, water supply and management, waste-water discharge permits, and protection of endangered fish habitat.

The USGS Office of Surface Water (OSW) has partnered with ESRI, Inc. to develop a prototype Web application named StreamStats that greatly reduces the time needed to estimate streamflow statistics for ungaged sites and to make published streamflow statistics for USGS data-collection stations easily accessible. A prototype version of StreamStats is currently working for Idaho. This prototype can be viewed at http://streamstats.usgs.gov. The USGS is working to implement the program in several other states.

Figure 1. Prototype StreamStats Web application user interface.

What is StreamStats

StreamStats is an integrated Geographic Information System (GIS) application that uses ArcIMS, ArcSDE, ArcGIS, and the ArcHydro Tools to make the process of computing streamflow statistics much faster, more accurate, and more consistent than previous manual methods. StreamStats incorporates (1) a map-based user interface for site selection (figure 1), (2) a database that provides streamflow statistics and other information for data-collection stations, (3) a GIS program that determines boundaries of the drainage basins for ungaged sites, measures the physical characteristics of the drainage basins, and solves regression equations to estimate streamflow statistics for the sites, and (4) a GIS database needed to display maps and determine the physical characteristics of the drainage basins. When implemented for individual states, users can obtain previously published streamflow statistics and other information for USGS data-collection stations by clicking on the station locations in the StreamStats user interface. Users also can obtain estimates of streamflow statistics and basin characteristics for ungaged sites by clicking on the site locations in the interface.

Data-Collection Site Database

A new database, named StreamStatsDB, has been developed to be populated with descriptive information, basin and climatic characteristics, and streamflow statistics for the data-collection sites throughout the Nation. The database has an easy-to-use data entry interface and the ability to read descriptive site information, and basin and streamflow characteristics for data-collection sites from other USGS databases and from spreadsheets. The initial release of the database contains 144 types of basin and climatic characteristics and 492 types of streamflow statistics. Each streamflow statistic in the database has an associated standard error of estimate. All USGS-developed regression equations for estimating peak-flow frequency statistics were reviewed to determine the basin and climatic characteristics needed initially in the database. Users can insert additional characteristics to the database when needed. When populated, StreamStatsDB will be useful for regional analyses as well as for the StreamStats Web application.

User Interface

The StreamStats user interface (figure 1) works through a Web browser window on the user's desktop. Initial functionality for the interface includes the ability to:

• Display default base map data layers at specified scales
• Display data-collection site locations
• Pan and zoom to areas of the map
• Identify features of selected map layers
• Zoom to specific places in the USGS Geographic Names Information System (GNIS), such as towns, counties, river basins, etc.
• Zoom to a water feature, such as the name of a river or lake
• Zoom to street addresses
• Zoom to specified coordinates (latitude, longitude)
• Print the map shown in the map frame
• Download the map data shown in the map frame
• Display descriptive information, basin characteristics, and flow statistics for data-collection sites
• Determine basin boundaries for user-selected ungaged sites and check the boundaries determined by the program against topographic maps shown in the background
• Determine basin and climatic characteristics needed to solve regression equations for ungaged sites
• Estimate streamflow statistics for ungaged sites using regression equations and provide standard errors of estimate or prediction and confidence intervals, where available, for each state and hydrologic region within the basin boundary

GIS Data

StreamStats can measure the physical and climatic characteristics of the drainage basins for user-selected sites from national datasets developed by the USGS and other agencies, such as the

• National Hydrography Dataset (NHD),
• National Elevation Dataset (NED)
• Elevation Derivatives for National Applications Dataset (EDNA),
• National Land Cover Data (NLCD),
• Watershed Boundary Dataset (WBD),
• Parameter-elevation Regressions on Independent Slopes Model Dataset (PRISM), and
• State Soil Geographic Database (STATSGO).

Many areas of the U.S. have GIS data that are of higher accuracy or that contain different information than is available from the national datasets. Local datasets can be used where they are of higher accuracy than national datasets, and where they are necessary to solve the local regression equations.

The GIS data will be organized by 8-digit hydrologic accounting units (HUC's). The data structure follows the design of the ArcGIS Hydro Data Model (for the most recent version of the ArcHydro Tools, please contact the StreamStats development team at GS-W Streamstats@usgs.gov).

Regression equations

The National Flood-Frequency Program (NFF)is a computer program that solves USGS peak-flow frequency regression equations for every State. The program relies on manual entry of the basin and climatic characteristics needed to solve the regression equations. NFF was modified to serve as a subroutine of StreamStats and to solve all types of regression equations; not just equations for estimating peak flows.

Implementation

StreamStats is currently working for all of Idaho, and work is underway to implement it in several other states during fiscal year 2005 and beyond (fig. 2). In addition, several enhancements in functionality are planned during fiscal year 2005, including the ability to edit drainage-basin boundaries and to obtain a large suite of basin characteristics for any site on a stream. Implementation for individual States requires that the respective USGS District offices complete the following work: (1) prepare any needed GIS data, (2) populate and quality assure the StreamStats database with streamflow statistics and other information for data-collection stations, and (3) test the ungaged-site process to verify that the results are statistically equivalent to previously published values in USGS reports. Implementation generally is done through cost-sharing cooperative agreements with State and local agencies.

Figure 2. Map showing where StreamStats is implemented, in red, and where implementation work is being done, in blue.

Talks and other information

StreamStats: A U.S. Geological Survey Web Application for Stream Information (FS 2004-3115)

Presentation at USGS headquarters September 9, 2003

StreamStats was the subject of a session at the SYMPOSIUM ON TERRAIN ANALYSIS FOR WATER RESOURCES APPLICATIONS, December 16-18, 2002, at the University of Texas - Austin

Parts 1 and 4 StreamStats: A U.S. Geological Survey Web Application for Obtaining Streamflow Statistics for Gaged and Ungaged Sites

Part 2 StreamStats: System Design and Web Implementation

Part 3 Data Requirements for StreamStats

Hydroinformatics 2002 Conference in Cardiff, Wales, July 1-5, 2002