Definition and Connection of Hydrologic Elements using Geographic Data

Constructing a lumped parameter hydrologic model of a watershed involves dividing the watershed into subbasins and determining their connectivity through the stream network. Subbasin boundaries and stream networks can be described by Geographic Information System (GIS) data layers derived from digital terrain analysis or digitized from maps. By intersecting the subbasin and stream network data layers, then interpreting the resulting geographic features, it is possible to construct automatically a node-arc network description of the watershed comprised of connected hydrologic elements, including subbasins, reaches, junctions, reservoirs, diversions, sources, and sinks of flow to and from the watershed. The procedure, called CRWR-PREPRO, has been automated in Arc/Info Arc Macro Language (AML) and ArcView Avenue programs, which produce an ASCII file readable by the Hydrologic Engineering Center's Hydrologic Modeling System (HEC-HMS). A step-by-step procedure for interpreting geographic data to identify hydrologic elements is presented using a modified version of the Tenkiller Reservoir watershed in Oklahoma as an example. A further example application is presented of the application of CRWR-PREPRO to the Upper Mississippi basin and part of the Missouri basin, which results in a hydrologic model containing more than one thousand hydrologic elements.