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Researchers develop scalable flow‑ecology curves to assess North Coast stream risk
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Summary
Lara, a freshwater ecologist at SCORP, outlined a method to build flow‑ecology response curves linking modeled functional‑flow metrics to algal and macroinvertebrate bioassessment indices for the North Coast.
Lara, a freshwater ecologist at the Statewide California Office of Regional Projects (SCORP), described work to develop “flow ecology curves” that predict how changes in streamflow affect algal and invertebrate bioindicator indices and, ultimately, habitat suitability for sensitive species.
Her team combines modeled functional flow metrics with statewide bioassessment indices (ASCII for algae and CSCI for macroinvertebrates), then reduces and fits metrics using boosted regression trees and generalized linear models to produce response curves that can be applied even at unmonitored reaches.
The analysis identified 10‑year flood magnitude and the timing of 7‑day minimum flows as among the most important predictors for algal and invertebrate condition; dry‑season baseflows and the timing of lowest flows were also highlighted as likely to be most altered by diversions and most amenable to management.
“We’ve been looking at developing these flow ecology curves to address ecological risks in terms of flow alterations in the Northern Coast,” Lara said. “The alcum pumie seems to be generally responding more so to changes in the flood magnitudes, while the invertebrates are more so responding to changes in timing and duration.”
In audience questions, Lara said the team plans to integrate flow and temperature in other case studies and advised that a bare minimum dataset for regional curve development includes several years of gauge data and roughly 50 bioassessment sites to reduce model uncertainty.
The curves are intended to be used with habitat‑suitability analyses to map ecological risk and to inform water‑management decisions such as distributed diversion controls and timing adjustments.
While the project is presented as a test case for the North Coast, the researchers said the approach is designed to be scalable to other regions where sufficient flow and bioassessment data exist.
