Framework developed for establishing Southern California stream flow thresholds

SCCWRP and its partners have completed development of a framework that can be used to establish ecologically relevant flow targets for stream sites across Southern California.

The framework, which relates flow alterations to biological indicators of stream condition, marks the final

The study, conducted in partnership with Colorado State University and the U.S. Geological Survey, used a scientific framework known as the Ecological Limits of Hydrologic Alteration (ELOHA) to evaluate minimum environmental flow requirements at more than 800 ungauged stream sites across Southern California.

The study involved establishing preliminary thresholds for each of five flow metrics identified as being the most influential indicators of biological condition; flow augmentations or depletions beyond these flow thresholds are expected to be associated with declines in biological condition. The project’s technical advisory committee reviewed the initial analysis at a March meeting.

The project’s goal is to understand how to apply flow-ecology relationships to optimally balance the often-conflicting goals of maintaining water supply, improving water quality and supporting in-stream health.

Already, the preliminary regional flow thresholds that were developed through this work have been applied to an ELOHA case study in the San Diego River watershed to inform restoration efforts and other management actions.

Drafts of the final project reports are expected to be ready this summer.