This study presents a web-based spatial decision support system (SDSS) that supports watershed analysis from an economic perspective. The SDSS is intended to aid the development of sediment TMDLs sediment on rangeland watersheds. The SDSS architecture consists of three parts: the interface tier, the application tier, and the data tier. Middleware is used to integrate these three parts into one system. Dynamic web pages are used to support customized access to the system, including defining inputs, running analysis and viewing results. The middleware is used to glue the interface, model, and database together seamlessly. The embedded models include geospatial models and a watershed optimization model. The database is used to manage all the data through web-based interfaces. The SDSS supports spatial inputs, such as pasture boundaries, water points and stock ponds, and nonspatial inputs, such as cost scenarios, sediment control objectives and policy options. An embedded representative ranch model is used to optimize management options to meet profit and sediment yield objective. The screenshot for of the SDSS for the Walnut Gulch Experimental Watershed are used to illustrate the major functionality of the SDSS in assessment of Best Management Practices (BMPs) in soil conservation plans.