UNDERSTANDING STREAM SEDIMENT SOURCES FOR WATERSHED WATER QUALITY MANAGEMENT

Information on the relative contribution of different watershed sediment sources is a key requirement for targeted management strategies for sediment control and water quality management. In the United States, about 15% of assessed stream miles are considered threatened or impaired with respect to suspended sediment (USEPA, 2008). Section 303(d) of the 1972 clean water act requires states in the US to develop Total Maximum Daily Loads (TMDLs). A TMDL is a calculation of the total amount of a pollutant that a waterbody can receive without violating water quality standards. A number of tools from various geosciences disciplines (e.g., geochemistry, geomorphology, hydrology, soil science, water resources engineering) are being used in developing sediment TMDLs. The goal of this presentation is to review the various methods used for sediment source assessment for watershed water quality management with a focus on sediment fingerprinting. Sediment fingerprinting is a direct method of assessing sediment sources in a watershed that has been developed in recent years. The technique is based on the assumptions that watershed sediment sources can be discriminated by a number of different diagnostic physical and chemical properties, and comparison of properties of suspended sediment with those of potential sources permits relative importance of sources. Case studies, research needs and potential challenges in the application of this approach as a regulatory tool will be discussed.