QA

Studies to Evaluate Differences Between Ascending and Descending Limbs of the Hydrograph

COA 10.21.10 Approved Active Fieldwork

Focal Species

Winter-run Chinook salmon Spring-run Chinook salmon

Winter-run and spring-run Chinook salmon out-migrants are the primary focal taxa: the study measures how their movement and survival respond to the rising versus falling limbs of the river hydrograph, generating the empirical difference signal that the operating-criteria evaluation (COA 10.18.3) consumes.

Project Effect Links

Far-field. Real-time diversion changes the rate-of-change of river stage and flow on both the ascending and descending limbs. This study isolates the biological difference between the two limbs so COA 10.18.3 can develop operating criteria that minimize impact rather than averaging across the hydrograph.

Objectives, Research Questions & Hypotheses

Generate the empirical ascending-vs-descending-limb difference in fish movement, distribution, and apparent survival, and hand off the calibrated data and models to COA 10.18.3 by Q1 2029. The study pairs flow-event sampling with split-beam hydroacoustic monitoring keyed to rising and falling limb events.

  1. Does fish movement and apparent survival differ between the ascending and descending limbs of comparable flow events?
  2. Which limb characteristics (rate-of-change, magnitude, antecedent condition) best explain the observed biological difference?

Background

Synthesizes the covered-species monitoring suite (COAs 10.18–10.21) and prior split-beam hydroacoustic and flow-event sampling in the Sacramento River. The study is back-scheduled from a firm Q1 2029 handoff so its calibrated limb-difference data and models are available to the operating-criteria evaluation (COA 10.18.3).

Methods

  • Split-Beam Hydroacoustic Monitoring
  • Flow-Event Sampling (ascending vs. descending limb)
  • Limb-Difference Analysis
  • Data and Model Handoff to COA 10.18.3

Performance Metrics

  • Apparent survival difference between limbs by flow-event class
  • Movement rate and direction by limb
  • Limb-characteristic covariate effect sizes

Data Management

Hydroacoustic detections and flow-event covariates are versioned in the DCP fisheries data system with event-level provenance; the calibrated limb-difference dataset and analysis code are packaged for handoff to COA 10.18.3.

Reporting Requirements

Draft and Final Study Plan (CDFW-approved); Draft Interim Reports; Draft Final Report and Final Report, completed by Q1 2029 to feed the operating-criteria evaluation. Final Report may contain a recommendation to update diversion criteria.

Agency Review — CDFW 3

0 open 1 addressed 2 resolved

Pinned to: Background

  • C
    CDFW CDFW 2026-03-10 Fix COA cross-reference Resolved

    The MMRP references 10.18.2 while the ITP references 10.18.3 as the downstream consumer. Note the discrepancy so the dependency edge is unambiguous.

    • GM
      Greenwood, Marin 2026-03-16

      Both numbers noted with the ITP (10.18.3) as the operative downstream study; discrepancy flagged.

Pinned to: Performance Metrics

  • C
    CDFW CDFW 2026-02-18 Add / adjust metric Addressed

    Please report the limb-difference effect size with confidence intervals by flow-event class, not as a pooled point estimate — the handoff to 10.18.3 needs the uncertainty propagated.

    • GM
      Greenwood, Marin 2026-03-02

      Metrics now report effect size with CIs per flow-event class; uncertainty is carried into the handoff package.

Pinned to: Reporting Requirements

  • C
    CDFW CDFW 2026-02-18 Governance / approval Resolved

    Confirm the Q1 2029 handoff date is firm — 10.18.3 is back-scheduled from it. State the date explicitly in the reporting requirements.

    • GM
      Greenwood, Marin 2026-02-27

      Q1 2029 handoff is firm and now stated explicitly. Schedule reflects the back-scheduled dependency.

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