Ecological Flow Linkages: Identifying Relevant Literature and Recent Advances

Stream flow is a critical, yet complex driver of ecological processes in streams.  Numerous studies have attempted to identify metrics that best represent hydrologic alteration caused by dams, diversions, withdrawals, land use, and other anthropogenic activities.  However, there is no consensus on how these hydrologic indices are linked to ecological processes and fishes.  The science related to ecological flows is rapidly evolving and many studies may not be published or are in progress.  Our objective was to determine the number of studies that identify biological links to stream flow alteration metrics.  We summarized metrics used to link flow alteration to biological responses from over 400 references including peer-reviewed literature, agency reports, flow assessment programs, and software. Our review showed that there are over 100 stream flow metrics used, but only a small fraction directly linked to a biotic response.  More common metrics linked to biotic responses included changes in mean annual flow, monthly flows, peak flows and variability (CV).   Any successful method in determining ecological flows needs to account for the relationships between flow and ecological response.  Our review will help identify future research needs and provide examples of flow metrics that could be incorporated into ecological flow assessments.