Evaluation of Restoration Alternatives in the San Joaquin River Using the Ecosystem Diagnosis & Treatment Model

The potential benefits of habitat restoration for spring-run Chinook in the San Joaquin River were evaluated to provide guidance to the San Joaquin River Restoration Program. A salmonid habitat model, Ecosystem Diagnosis & Treatment, was used to compare project alternatives related to floodplain restoration and flow routing to a base condition. The base condition and alternatives assumed SJRRP settlement flow and full fish passage. The absence of an existing population required assumptions about where and when fish would utilize habitat. Juvenile life histories were segregated into four strategies related to juvenile emigration and rearing location and were analyzed separately and together. Successful juvenile behavior within the model was to emigrate before water temperatures increased or remain over summer in cool water below Friant Dam; adults needed to move upstream early and quickly to cool water below the dam. The predicted results of floodplain restoration depended on the trade-off between flow management to achieve cooler water temperatures in spring for adult and smolt migration, and to provide floodplain inundation in winter for fry and parr migration. The greatest modeled benefit to spring-run Chinook was from restoring floodplain habitats throughout the 150-mile project area and not splitting flows into separate channels.