Solutions for Progress 

Cosumnes River Flow Augmentation Project

The Cosumnes River Flow Augmentation Project supplements the flow of the Cosumnes River by releasing up to 5,000 acre-feet of water into the Cosumnes from the Folsom South Canal. The project objectives are listed below.

  • Improve fall-run chinook salmon migration conditions by allowing the Cosumnes River to connect to tidewater earlier in the fall, and sustaining surface flow continuity in the Cosumnes River after its initial connection.
  • Evaluate the rate of groundwater recharge from the river channel between the Folsom South Canal and Twin Cities Road to better guide future groundwater management and environmental restoration efforts along the Cosumnes River corridor.

RBI assisted the Southeast Sacramento County Agricultural Water Authority and The Nature Conservancy in negotiating an agreement with the Sacramento County Water Agency for a long-term water supply for the project. RBI also manages the implementation of the project.

In 2005, the Pilot Project Phase was implemented with a temporary water supply from the Central Valley Project - B2 Environmental Water Program. The Pilot Project demonstrated that it is possible to mimic historical river conditions by releasing supplemental flows into the Cosumnes River from the Folsom South Canal. These conditions supported a more successful fall migration of chinook salmon to the spawning areas at the base of the Sierra foothills.

RBI will manage the long-term annual implementation of the Flow Augmentation Project on behalf of the SSCAWA, SCWA and TNC. The project will allow biologists, scientists, and water managers to improve:

  • the timing of fall-run chinook salmon migration,
  • the success of chinook salmon spawning,
  • understanding of channel loss rates to groundwater, channel storage, and evapotranspiration, and
  • understanding of surface water and groundwater interaction affecting groundwater recharge rates from the Cosumnes River channel.