Water‐Quality Modeling with EPA Reach File System

Abstract

The U.S. Environmental Protection Agency (EPA) has developed a geographically referenced data‐base system of the surface‐water features of the United States. This data‐base system is called the Reach File. It was designed to serve as a foundation for water‐quality modeling, for storing and using stream‐network information, for topologically indexing other water‐resource data bases so that they may be accessed within a common analytical framework, for generating digital base maps of hydrographic features in user‐selected areas for water‐quality reporting and analysis, and for producing gazetteers of streams, lakes, and open waters. The Reach File serves as a cornerstone for data integration in EPA water programs, and as a major geographic information resource for water‐quality modeling and analysis. This paper briefly describes the Reach File and a system called the Routing and Graphical Display System (RGDS) that uses the Reach File and associated files to model and display water quality. The combination of the Reach File System and the modeling and display capabilities of RGDS may be viewed as a specialized network‐oriented geographic information system for surface‐water‐related analyses.