The Automated Geospatial Watershed Assessment (AGWA) tool is a desktop application that uses widely available standardized spatial datasets to derive inputs for multi-scale hydrologic models (Miller et al., 2007). The required data sets include topography (DEM data), soils, climate, and land-cover data. These data are used to develop input parameter files for two USDA-ARS watershed runoff and erosion models: the Kinematic Runoff and Erosion Model (KINEROS2, Smith et al., 1995; http://www.tucson.ars.ag.gov/kineros) and the Soil and Water Assessment Tool (SWAT, Arnold et al., 1994; http://www.brc.tamus.edu/swat/). AGWA has proved to be a useful tool for many different applications. Not all potential users, however, have access to the geospatial data or software required to process it and run tools like AGWA. In addition, some potential users recognized the value in being able to use the application, but did not have adequate technical training to gather and process the necessary data and run the application through a geospatial information system (GIS) software platform. A Web-based version of AGWA, DotAGWA, was developed to address these issues and cater to a wider potential user audience. This paper describes the design and structure of the DotAGWA application and discusses important findings related to issues and problems that emerged during application development. In particular, important issues emerged related to configuring a system that would connect surface water models, originally intended as desktop applications, to a spatially enabled web application. Some of these issues include input and output file management for model runs when models are executed from the web-client to the server's operating system, configuring the systems spatial and non-spatial data requirements in a web server environment, and designing an extensible or at least reusable system architecture. The United States Environmental Protection Agency through its Office of Research and Development partially funded and collaborated in the research described here under assistance agreement DW12922094-01-0 to USDAARS. It has been subjected to Agency review and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.