UC Santa Cruz

Dams have been built on most of the world’s large rivers, making the management of environmental flows crucial for meeting the needs of humans and wildlife. Current water management in the mainstem Sacramento River below Keswick Dam focuses on maintaining optimal conditions for early life stages of endangered winter-run Chinook salmon (Oncorhynchus tshawytscha) and providing discharge to support downstream water use. We found that the low temperature and high discharge flows may negatively impact condition of threatened green sturgeon (Acipenser medirostris) larvae rearing in this region. We developed a multi-object optimization model which identified optimal releases of 11.5°C and 150 CMS to balance the three objectives. Reservoir levels required to meet this optimal management strategy occurred in 80% of the last 20 years. This proposed management strategy shifts to multi-object management while meeting downstream water requirements and could be used as a model to provide environmental flows in other impounded rivers.