Author(s): Sarah M. Yarnell; Eric D. Stein; Rob A. Lusardi; Julie Zimmerman; Ryan A. Peek; Theodore Grantham; Belize A. Lane; Jeanette Howard; Samuel Sandoval-Solis
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Keywords: No Keywords
Abstract: The scientific literature on flow metrics and quantification of flow regimes is vast, and a majority of approaches seek to link hydrology to ecology by determining which metrics are ecologically significant. These approaches have furthered understanding of flow-ecology relationships, but have focused attention on a narrow set of flow metrics that relate to biological indicators and fail to capture important aspects of flow regime variation upon which stream ecosystems depend. We suggest that functional flow components, defined as elements of the natural flow regime known to sustain important ecosystem processes and functions, provide a conceptual model for linking ecological theory with discrete, quantifiable measures of the flow regime. Functional flow components, such as winter floods or spring recession flows, can be quantified by flow characteristics, such as magnitude, timing, duration, frequency and rate of change, which are in turn measured by specific flow metrics, such as Julian day (timing), 5% exceedance flow (magnitude), or daily percent decrease in flow (rate of change). By selecting a suite of flow metrics that measure key flow characteristics of ecologically-relevant flow components, the spatial and temporal complexity of flow regimes can be quantified in a manner supportive of ecological processes and aquatic species requirements. In this manner, we emphasize the ecology of river ecosystems when quantifying environmental flow regimes by relying upon a priori hypotheses regarding the role of functional flow components and related flow metrics in supporting river-dependent species and communities. We illustrate our conceptual model by drawing upon research experience from the western United States, and discuss the applicability of the approach for prescribed flow designs, management and monitoring.
Year: 2018