Land use and land development adversely affect water quality in many substantial ways. The current land use regulatory system is blamed for its failure to plan and regulate to protect water quality and watershed health, and a frequent suggestion is to move authority for land use planning and regulation to larger ecologically-based scales, such as watersheds, or to regional, state, or national agencies that can act on a watershed scale. Despite the allure of these proposals, careful study of the scales and functions of watersheds and the scales and functions of land use presents a nuanced picture of both watershed and land use dynamics, suggesting that watershed institutions might be best suited for watershed planning, technical assistance, facilitation of intergovernmental cooperation, and provision of resources and information, while local governments will continue to be best suited to engage in generalized planning, zoning, permit decisions, and other traditional regulatory functions. This article discusses the impact of land use on water quality, and then explores the scale and function of both watersheds and land use. It offers lessons about the geographic, functional, problem, and temporal scales of watersheds, and the functional, political, resource, and temporal scales of land use, as well as lessons about the legal scale of freedom and boundaries. Attempting to connect both the scale and function of watershed with both the scale and function of land use, the article recommends a hybrid regional-local model of watershed-based planning and regulation of land use
