The North Delta Routing and Survival Management Tool (ver. 3.0, May 2026)

Understanding how routing modifications influence survival of juvenile Chinook salmon (Oncorhynchus tshawytscha) is complex because reach-specific survival and routing at key river junctions in the North Delta each have a different relationship with river flow. Therefore, to facilitate understanding of how routing modifications at key river junctions influence through-Delta survival, we developed this spreadsheet model to allow managers to explore the potential effects of modifying routing. The purpose is to provide a screening tool that allows managers to quickly run many different scenarios to understand how both routing and route-specific survival interact to affect overall survival through the Delta. In May 2026, version 3.0 was released, which allows managers to evaluate the sensitivity of through-Delta survival to different routing management actions at multiple locations in the North Delta. This tool may be useful in narrowing the range of potential scenarios that might be investigated using more complex modeling techniques (e.g., agent-based models) and eventually evaluated with field studies. Previous versions can be obtained from the authors.