Sustainability of water supplies for downstream industrial, municipal, and agricultural needs is largely dependent on the flow of water from upland watersheds in the upper reaches of the larger river basins in the region. Many of the water systems in the southwestern United States flow only in response to intermittent precipitation or short-term snowmelt-runoff events. Contribution of these water systems to downstream water supplies, therefore, is largely in the form of stormflow. Impacts of land use practices implemented on upland watersheds become a concern of water managers when the practices impair the quality of stormflow. The general impacts of land use practices, both good and bad, on the quality of stormflow from upland watershed in the southwestern United States are reviewed in this paper.