Keystone Initiative: Central Valley Fish and Floodplains

Salmon Habitat on Rice Fields – A Model for Ag, Flood Protection, and Fish.

CalTrout’s work in the Central Valley is addressing California’s defining environmental challenge: How do we reconcile ecosystem function with human needs in the face of a changing climate? Operating at the nexus of water supply, flood protection, agriculture, and fish and wildlife conservation, the Managed Agricultural Habitat project is laying the scientific and political groundwork for precedent-setting water solutions with multiple benefits for both fish and people. The work demonstrates that California can have both its fish and its farms.

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About Salmon Habitat on Rice Fields

Nicknamed the Nigiri Project (think salmon over rice), the project began on the rice fields of Knaggs ranch in Yolo Bypass in 2012, and has expanded annually. It now encompasses research sites throughout the Sacramento and San Joaquin Valleys. By rearing salmon in flooded winter farm fields the project has documented that fat, robust, healthy salmon grow many times more quickly than salmon in adjacent river channels. These results have come from different watersheds (Sacramento, Feather, Cosumnes and San Joaquin); from different water sources, (river water, canal water, ground water); from different kinds of fields (rice, winter wheat, weeds, bare dirt). In each instance the simple process of spreading and slowing floodwaters over the floodplain resulted in phenomenal growth rates for the young salmon. Fish food is primarily made on the floodplain not in the river channels. Just as agricultural crop plants convert sunlight and soil nutrients into food for people, fish food is created as sunlight falls on the floodplain. In winter, when floodwaters spread out over the floodplain, summer plant material becomes available to the aquatic food web where it’s broken down and turned into bug food. Algae (called phytoplankton by scientists) floating near the surface of floodwaters also uses photosynthesis to convert solar energy into food energy; sunlight makes algae, algae makes bugs, bugs make fish.

This simple but incredibly productive food web was the engine of productivity that supported prolific populations of fish and waterfowl in the pre-development Central Valley. But over the last century construction of levees has cut off 95% of the Central Valley’s floodplains from its rivers. Today, Central Valley aquatic ecosystems no longer receive the solar energy needed to support the aquatic food web and sustain abundant fish and wildlife populations. Recovery of endangered fish populations is impossible without first recovering the ecological processes which supported them. In order for California’s water system to provide water security for people, threatened fish populations must have access to the abundant food created on floodplains.
CalTrout’s research demonstrates that restoring ecological function is possible, even in intensively managed landscapes like the Central Valley, by mimicking natural flood patterns on working agricultural floodplains. Recovering salmon and smelt populations, even during times of drought, is possible when this science is turned into action and California’s outdated water infrastructure is updated to allow more frequent and longer duration floodplain inundation. Floodplain reconnection will also improve flood protection, increase aquifer recharge and generally increase resiliency of both the aquatic ecosystem and California’s water supply to increasingly extreme droughts and floods.

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