When water enters Putah Creek Nature Park, it enters a deep old gravel pit, slows down, and warms up due to the lack of movement and shade. Just as a warm soda has fewer bubbles than a cool soda, warm water has less oxygen. Warm water is less productive for native wildlife, in part because the bubbles—or dissolved oxygen which fish and insects breathe—are critical to their survival.
The excessively wide and deep form of the channel is a double-whammy for water temperature. The width increases exposure to the sun, while the depth decreases flow velocity so the water stays in the warm pool for a longer time.
The narrowed, shallower channel created by the Realignment Project will increase flow, thus increasing bubbles and dissolved oxygen and reduce warming time. The narrowed channel will allow a full canopy of trees to branch out over the channel, fully shading the water to limit solar warm up.
The narrowed channel will also help move gravels downstream from Putah Creek’s confluence with Dry Creek. Dry Creek is furthest downstream tributary to Putah Creek, and a critical source of gravel for the creek since nearly all other gravel sources are trapped behind dams.
The influx of gravel will provide places for native aquatic insects to reproduce, and will provide spawning habitat for fish, including salmon. This project will help ensure the gravels make it downstream to areas they can be utilized by fish and insects
Once the project is complete, it will also provide more habitat for native fish. Fish need places to hide, feed, and spawn. The project will install rock structures, called weirs, and walnut root wads in the channel to help create habitat where fish can hide, and help diversify the under-water structure available to aquatic wildlife.
Local residents and visitors will also benefit from the project. The project includes 2,400 feet of 10-foot-wide nature trail on the north bank. The paved trail will allow bikes, pedestrians, and emergency access by authorized personnel. Additional foot trails along the newly created banks will be accessible during low-flow months. The south bank will have a gravel walking trail from the Car Bridge to the Interstate 505 bridge.
The long term vision is to have an additional pedestrian bridge downstream of the existing pedestrian bridge, making a loop trail through the park. There is currently no funding for an additional bridge, but the trails on both the north and south bank provide the first elements of making this vision a reality.
Major project funders include California Natural Resources Agency: River Parkways program via propositions 50 and 84 (clean water and parks bonds).