Complexities of the Sediment Fingerprinting Approach -- With Examples from the Chesapeake Bay Watershed and Lake Tahoe

Sediment fingerprinting is an approach used to determine the relative magnitude of contributions from the important sources of fine-grained sediment in a watershed. Sediment-fingerprinting results show the contribution from each source over specific time periods -- seasons, individual flow events, and across a given storm hydrograph. Although the gross contribution of watershed sources can be identified for a given time period, the precise location within the watershed and the relative contributions of a given source of sediment (i.e., streambanks) must be identified through another process, such as using a sediment budget approach. Important research obstacles in the sediment-fingerprinting approach that still need to be evaluated include the determination of the: (1) appropriate watershed scales for this approach, (2) effects of grain size and organic content on fingerprint properties, (3) suitable physical and chemical tracers for fingerprinting, (4) conservativeness of fingerprint properties through the erosion cycle, (5) appropriate statistical approaches to determine the significant fingerprints and relative contributions of each source, and (6) effects of storage and delivery times on sediment sources for a particular event. This poster presents the sediment fingerprinting approach that was used in watersheds draining to the Chesapeake Bay and Lake Tahoe with a discussion of the problems encountered.