Land use management approaches and changes in land use can have significant impacts on hydrology, water quality, and other aspects of the environment. Nonpoint source pollution in the United States causes nearly $10 billion in damage yearly. A WWW-based decision support system has been developed to examine the effects of agriculture, urbanization, and land use management practices on the hydrology and water quality of these areas. Many of the parameters and processes affecting hydrology and water quality vary spatially. Thus, GIS has been integrated with models, large databases, and other information systems tools to create the decision support system.