GIS and distributed watershed models. 1: Data coverages and sources

The increasing proliferation of spatial data, geographic information systems (GIs), and models for hydrologic applications provide many new investigation opportunities but also present a number of challenges for the uninitiated water resources practitioner. This two-part paper is intended for the practicing engineer who wants to expand into the arena of spatial data and distributed watershed modeling. It provides an integrated overview of the multiple facets of data-GIS-modeling issues and a source of background information for selection and application of GIS in watershed modeling. This first paper addresses selected spatial data issues, data structures and projections, data sources, and information on data resolution and uncertainties. Spatial data that are covered include digital elevation data, stream and drainage data, soil data, digital orthophoto data, remotely sensed data, and radar precipitation data. The focus is on data and issues that are common to many data-GIS-modeling applications. The second paper presents issues on and examples of GIs and hydrologic models and provides recommendations with respect to organization and implementation of the integrated use of spatial data, GIS, and distributed watershed models.