EPA's Experimental Stream Facility: Design and Research Supporting Watershed Management

The EPA's Experimental Stream Facility (ESF) represents an important tool in research that is underway to further understanding of the relative importance of stream ecosystems and the services they provide for effective watershed management. The ESF is operated under the goal of supporting the integration of risk assessment and management research objectives for water quality protection with controlled studies designed to characterize how streams react to and process emerging contaminants and stressful mixtures. The engineering aspects of the ESF set-up are described that allow for a balance between controlled laboratory conditions and the natural variability that is inherent to stream ecosystems, and that are required for adequate ecological simulation. Flow distribution is configured so that real stream water is delivered to eight mesocosms allowing for natural and optimal colonization while controlling for water residence time and hydraulic properties of riffle microhabitat. Single contaminants or stressful mixtures can be precisely dosed. Characteristics such as light intensity, influent water quality, and streambed substrate type can be manipulated within and across studies. Each ESF study provides information on ecosystem structure and function that can be used in relation to the development and testing of new indicators of ecological stress, water quality monitoring technologies, and water quality management methods and models.