Using the STARS Model to Evaluate the Effects of the Proposed Project for the Long-Term Operation of the State Water Project Incidental Take Permit Application and CEQA Compliance

Open-File Report 2019-1127
Prepared in cooperation with California Department of Water Resources
By: , and 

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Abstract

The California Department of Water Resources (DWR) requested analysis of juvenile Chinook salmon survival in the Sacramento-San Joaquin River Delta (henceforth identified as “the Delta”) as part of an effects analysis that will be included in an Incidental Take Permit (ITP) Application. This application is in compliance with the California Endangered Species Act (CESA) and Environmental Impact Report (EIR), which is itself in compliance with California Environmental Quality Act (CEQA). DWR is seeking an ITP and preparing CEQA compliance documentation for long-term operation of the State Water Project (SWP). DWR requested assistance from the U.S. Geological Survey to aid in determining the effect of the proposed project on juvenile Chinook salmon (Oncorhynchus tshawytscha) populations migrating through the Delta. Therefore, in this report we analyzed an 82-year time series of simulated river flows and Delta Cross Channel (DCC) gate operations under two scenarios constructed for the ITP: the proposed project (PP) and the existing (EX) scenarios.

To evaluate the proposed project, we used the STARS model(Survival, Travel time, And Routing Simulation model), a stochastic, individual-based simulation model designed to predict survival of a cohort of fish that experience variable daily river flows during migration through the Delta. The STARS model uses parameter estimates from a Bayesian mark-recapture model that jointly estimates travel time and survival in eight discrete reaches of the Delta and migration routing at two key river junctions.

By applying the STARS model to the two 82-year scenarios, we found that the proposed project had negative effects on survival, travel time, and routing in November but slightly positive effects in October, December, May, and June. In November, there was a high probability that survival for PP was less than EX and that travel time and routing to the Interior Delta for PP were greater than for EX. We found that the magnitude of the difference in survival between scenarios was large in some years. For example, survival under the PP scenario was 10 percent lower than EX in 25 percent of the water years in November. During this period, inflow to the Delta tended to be lower under the PP scenario, and the DCC gate was open more frequently under the PP scenario relative to the EX scenario. Lower inflow reduces survival, and more frequent operation of the DCC gate 1) increases the proportion of fish entering the Interior Delta, where survival is low, and thus 2) reduces survival in the Sacramento River in reaches downstream of the DCC. In contrast, during October, December, May, and June, survival was slightly higher, travel times were lower, and routing to the Interior Delta was lower under the PP relative to the EX scenario in the same time period, although the magnitude of the increase was relatively small in most years (less than two percent). This difference between scenarios was driven by higher river flows in some years under the PP relative to the EX scenario. Overall, the differences in survival, travel time, and routing distance between the two operational scenarios were primarily driven by the timing and magnitude of the annual high river flows.

Suggested Citation

Perry, R.W., Hansen, A.C., Evans, S.D., and Kock, T.J., 2019, Using the STARS Model to evaluate the effects of the proposed project for the long-term operation of State Water Project Incidental Take Permit Application and CEQA compliance: U.S. Geological Survey Open-File Report 2019–1127, 31 p. plus appendixes, https://doi.org/10.3133/ofr20191127.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Abstract
  • Introduction
  • Methods
  • Results and Discussion
  • References Cited
  • Appendixes

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title Using the STARS Model to evaluate the effects of the proposed project for the long-term operation of State Water Project Incidental Take Permit Application and CEQA compliance
Series title Open-File Report
Series number 2019-1127
DOI 10.3133/ofr20191127
Year Published 2019
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Western Fisheries Research Center
Description Report: vii, 31 p.; Appendixes 1–4
Country United States
State California
Other Geospatial Sacramento-San Joaquin River Delta
Online Only (Y/N) Y
Additional Online Files (Y/N) Y