The San Francisco Public Utilities Commission (SFPUC), a department of the City and County of San Francisco (CCSF), owns and operates the Hetch Hetchy Water and Power Project, located in the upper Tuolumne River watershed in California’s Sierra Nevada.  The Hetch Hetchy Project is a system of major dams, diversion structures, and hydropower facilities on the Tuolumne River, Cherry Creek (a tributary to the Tuolumne River), and Eleanor Creek (a tributary to Cherry Creek).  The system supplies water to 2.6 million people in the San Francisco Bay Area and provides hydropower for Turlock and Modesto irrigation districts and San Francisco municipal uses.  

The project was authorized by the Raker Act, which was passed by the U.S. Congress in 1913 and granted the CCSF rights-of-way to certain public lands within Yosemite National Park and Stanislaus National Forest to develop water and hydropower resources.  
The Upper Tuolumne River Watershed
In general, dams, diversions, and hydropower facilities regulate the passage of water, sediment, and large wood to areas downstream.  Because water in particular acts as a “master variable” in river ecosystems, downstream riverine habitats depend on the pattern and quantity of water releases from dams and powerhouses. 

Through existing agreements with the U.S. Department of Interior, the major Hetch Hetchy Project dams are required to provide minimum water releases to downstream areas affected by their operations.  The project retains a statutory exemption in the Federal Power Act and instream flow releases are not subject to Federal Energy Regulatory Commission jurisdiction.  The existing minimum “instream” flow agreements are generally designed to provide for basic maintenance of trout populations. 

In June 2006, the SFPUC adopted the Water Enterprise Environmental Stewardship Policy, which requires the protection and rehabilitation of ecosystems affected by SFPUC water system operations, within the context of water supply, power generation, water quality, and existing agreements. The policy broadens the scope of SFPUC instream flow releases by requiring that they mimic, to the extent feasible, “…the variation of the seasonal hydrology (e.g., magnitude, timing, duration, and frequency) of their corresponding watersheds in order to sustain the aquatic and riparian ecosystems upon which native fish and wildlife species depend.”

Subsequent to adoption of the Stewardship Policy, the SFPUC initiated the Upper Tuolumne River Ecosystem Program (UTREP) with the goal of conducting long-term, collaborative, science-based investigations designed to:
  • Describe historical and present day upper Tuolumne River ecosystem conditions; 
  • Assess the relationship of historical and present day conditions to Hetch Hetchy Project operations; and
  • Develop recommendations for improving ecosystem conditions on a long-term, adaptively managed basis.
The UTREP develops data, analyses, and recommendations for improving ecosystem conditions downstream of Hetch Hetchy Project facilities consistent with the Stewardship Policy.  The UTREP is a project of the SFPUC, with numerous scientific collaborators, including the National Park Service (NPS) at Yosemite National Park, the U.S. Fish and Wildlife Service (USFWS), the U.S. Forest Service (USFS) at Stanislaus National Forest, consultants, researchers, and academics. Valuable input is also provided by the members of the Upper Tuolumne River Stakeholder Group