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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 part of Idaho. 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 will be able to 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 will be able to obtain estimates of streamflow statistics and basin characteristics for ungaged sites by clicking on the site locations in the interface.
An earlier StreamStats prototype was developed for Massachusetts. This application and documentation can be viewed on the Web at http://ststdmamrl.er.usgs.gov/streamstats/. The Massachusetts application uses custom GIS datasets and programming that could not be easily modified to work for other States. The new prototype has been designed for implementation in any state. It is faster and has more functionality than the Massachusetts application and it is more flexible in the type and resolution of the GIS data that it can use.
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.
- 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
- Planned additional functionality will include the ability to:
- Zoom to street addresses
- Zoom to specified coordinates (latitude, longitude)
- Work seamlessly for sites with basin boundaries in multiple states and/or regions by weighting the regression estimates obtained for each state/region according to drainage area within each state/region and standard error
- Estimate streamflow statistics for ungaged sites based on the flow per unit of drainage area of the statistics for streamgaging stations upstream or downstream from the ungaged sites
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
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.
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 is being modified to
serve as a subroutine of StreamStats solves all types
of regression equations; not just equations for estimating
peak flows.
Implementation
The prototype is currently working for part of Idaho. It is planned that StreamStats will be working for all of Idaho and for all or parts of Vermont, New Hampshire, Massachusetts, and Tennessee by September 2004. After Streamstats has been tested for the five prototype States, additional States will be added to the application as the respective USGS District offices are able to complete the following work: (1) prepare any needed GIS data, (2) populate the StreamStats database with streamflow statistics and other information for data-collection stations, and (3) test the ungaged-site process to verify that the values of the basin and climatic characteristics and the streamflow statistics obtained from StreamStats for gaging stations within the State are statistically equivalent to previously published values in USGS reports. Detailed directions for completing the work required to implement StreamStats will be provided to the USGS District offices when the prototype is completed. Implementation will generally be done through cost-sharing cooperative agreements with state and local agencies.
Talks and other information
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
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