Paradise Regained: Solution for restoring Yosemite's Hetch Hetchy Valley

Environmental Defense Fund (EDF) | July 15th, 2004

In this report Environmental Defense provides a planning-level analysis for replacing the water and hydropower benefits that the Hetch Hetchy Reservoir and O’Shaughness

In this report Environmental Defense provides a planning-level analysis for replacing the water and hydropower benefits that the Hetch Hetchy Reservoir and O’Shaughnessy Dam provide.We show how practical, proven water storage, conveyance and treatment alternatives can provide San Francisco a healthy, reliable and secure supply of water that is adequate for current and future needs.  We also explain how hydropower lost as a result of restoring the valley can be replaced without contributing to air pollution or global warming. The alternatives analyzed do not comprise all possible options, but they do demonstrate that workable solutions for restoring Hetch Hetchy Valley exist. We began this study with the premise that all solutions must be technologically feasible and affordable and must assure a dependable supply of safe drinking water. In addition to addressing the water and power needs of San Francisco and other Bay Area communities that rely on the Tuolumne River, solutions must also protect all affected California communities. Most obviously, any restoration plan must protect the Turlock and Modesto Irrigation Districts, whose uses of the Tuolumne River predate and are intertwined with those of the San Francisco Public Utilities Commission (SFPUC) and its customers. Of course, a restoration plan must also consider the Groveland area, both as a user of the Tuolumne River water and as a gateway community to the Hetch Hetchy region of Yosemite National Park. Our analysis focuses mainly on alternative ways to move and store San Francisco’s existing supply of Tuolumne River water. Environmental Defense developed the TREWSSIM (Tuolumne River Equivalent Water Supply Simulation) model to evaluate the SFPUC’s system performance under a range of water supply alternatives, with and without Hetch Hetchy Reservoir.TREWSSIM incorporates features of both the SFPUC’s planning model HHSM-LSM and the state-federal CALSIM model. The TREWSSIM analysis addresses not only water supply issues, but also water treatment and hydropower. Three expert consultants assisted in our analysis: Schlumberger Water Services provided engineering analyses and modeling assistance; Eisenberg, Olivieri and Associates analyzed water quality issues; and Somach, Simmons  & Dunn assessed the legal landscape. Academic experts provided peer review. The San Francisco Public Utilities Commission, the Bay Area Water Supply and Conservation Agency, and the Turlock and Modesto Irrigation Districts also provided information to help ensure an accurate report.

Petaluma Valley Historical Hydrology and Ecology Study

San Francisco Estuary Institute (SFEI) | March 1st, 2018

This study examines the historical hydrology and ecology of the Petaluma River watershed prior to major Euro-American modification, and analyzes landscape changes over th

This study examines the historical hydrology and ecology of the Petaluma River watershed prior to major Euro-American modification, and analyzes landscape changes over the past two centuries. Synthesizing information from hundreds of archival documents, the research reconstructs the historical form and function of wetland, riparian, and aquatic habitats and stream channels throughout the watershed, providing insights into habitat extent and distribution, streamflow and sediment dynamics, vegetation composition, wildlife support, and landscape change. Findings from this research can be used to help set restoration targets and to prioritize multi-benefit opportunities to restore wildlife habitat, enhance flood protection, increase groundwater recharge, and improve sediment management. This Executive Summary highlights key findings from the study. 

Primary Production in the Delta: Then and Now

University of California, Davis (UC Davis) | October 3rd, 2016

To evaluate the role of restoration in the recovery of the Delta ecosystem, we need to have clear targets and performance measures that directly assess ecosystem function

To evaluate the role of restoration in the recovery of the Delta ecosystem, we need to have clear targets and performance measures that directly assess ecosystem function. Primary production is a crucial ecosystem process, which directly limits the quality and quantity of food available for secondary consumers such as invertebrates and fish. The Delta has a low rate of primary production, but it is unclear whether this was always the case. Recent analyses from the Historical Ecology Team and Delta Landscapes Project provide quantitative comparisons of the areal extent of 14 habitat types in the modern Delta versus the historical Delta (pre-1850). Here we describe an approach for using these metrics of land use change to: (1) produce the first quantitative estimates of how Delta primary production and the relative contributions from five different producer groups have been altered by large-scale drainage and conversion to agriculture; (2) convert these production estimates into a common currency so the contributions of each producer group reflect their food quality and efficiency of transfer to consumers; and (3) use simple models to discover how tidal exchange between marshes and open water influences primary production and its consumption. Application of this approach could inform Delta management in two ways. First, it would provide a quantitative estimate of how large-scale conversion to agriculture has altered the Delta's capacity to produce food for native biota. Second, it would provide restoration practitioners with a new approach—based on ecosystem function—to evaluate the success of restoration projects and gauge the trajectory of ecological recovery in the Delta region.

Primary Production in the Sacramento-San Joaquin Delta: A Science Strategy to Quantify Change and Identify Future Potential

San Francisco Estuary Institute (SFEI) | May 20th, 2019

Today’s Sacramento-San Joaquin Delta is an unusually low-productivity estuary. The constraints on primary production and the relative importance of different production

Today’s Sacramento-San Joaquin Delta is an unusually low-productivity estuary. The constraints on primary production and the relative importance of different production sources to the food web are major ecological uncertainties in the Delta system. Understanding how the extensive historical changes in the Delta landscape have altered primary production has the potential to inform restoration planning and management across the region.  The Delta Landscapes Project (SFEI-ASC 2014) has recently produced information that allows us, for the first time, to answer questions about historical primary production and carrying capacity from quantified changes in the areal extent and spatial configuration of habitat types in the Delta since the mid-19th century. Our focus is on estimating primary production because the potential capacity of ecosystems to support fish, bird and other wildlife populations is set by primary production – the supply of food required to produce animal biomass. 

Programmatic Agreement among the U.S. Army Corps of Engineers and the California State Historic Preservation Officer and the Advisory Council on Historic Preservation and the Torres Martinez Desert Cahuilla Indians regarding Compliance with Section 106 of the National Historic Preservation Act for the Salton Sea Management Program

U.S. Army Corps of Engineers (USACE) | April 12th, 2024

Reconciling fish and farms: Methods for managing California rice fields as salmon habitat

PLOS | February 24th, 2021

Rearing habitat for juvenile Chinook Salmon (Oncorhynchus tshawytscha) in California, the southernmost portion of their range, has drastically declined throughout the pa

Rearing habitat for juvenile Chinook Salmon (Oncorhynchus tshawytscha) in California, the southernmost portion of their range, has drastically declined throughout the past century. Recently, through cooperative agreements with diverse stakeholders, winter-flooded agricultural rice fields in California’s Central Valley have emerged as ecologically functioning floodplain rearing habitat for juvenile Chinook Salmon. From 2013 to 2016, we conducted a series of experiments examining methods to enhance habitat benefits for fall-run Chinook Salmon reared on winter-flooded rice fields in the Yolo Bypass, a modified floodplain managed for flood control, agriculture, and wildlife habitat in the Sacramento River Valley of California. Investigations included studying the effect of 1) post-harvest field substrate; 2) depth refugia; 3) duration of field drainage; and 4) duration of rearing occupancy on in-situ diet, growth and survival of juvenile salmon. Post-harvest substrate treatment had only a small effect on the lower trophic food web and an insignificant effect on growth rates or survival of rearing hatchery-origin, fall-run Chinook Salmon. Similarly, depth refugia, created by trenches dug to various depths, also had an insignificant effect on survival. Rapid field drainage yielded significantly higher survival compared to drainage methods drawn out over longer periods. A mortality of approximately one third was observed in the first week after fish were released in the floodplain. This initial mortality event was followed by high, stable survival rates for the remainder of the 6-week duration of floodplain rearing study. Across years, in-field survival ranged 7.4–61.6% and increased over the course of the experiments. Despite coinciding with the most extreme drought in California’s recorded history, which elevated water temperatures and reduced the regional extent of adjacent flooded habitats which concentrated avian predators, the adaptive research framework enabled incremental improvements in design to increase survival. Zooplankton (fish food) in the winter-flooded rice fields were 53-150x more abundant than those sampled concurrently in the adjacent Sacramento River channel. Correspondingly, observed somatic growth rates of juvenile hatchery-sourced fall-run Chinook Salmon stocked in rice fields were two to five times greater than concurrently and previously observed growth rates in the adjacent Sacramento River. The abundance of food resources and exceptionally high growth rates observed.

Relationship between wetland condition, stress, and buffer

San Francisco Estuary Institute (SFEI) | April 25th, 2016

Relationship between wetland size and CRAM condition scores for depressional wetlands

San Francisco Estuary Institute (SFEI) | March 28th, 2016

Restoration of Hetch Hetchy Valley and San Francisco’s Water Supply

Restore Hetch Hetchy | February 10th, 2016

Q: After restoration, where will San Francisco gets is water? A: From the Tuolumne River, just as it does now. This report addresses only the most commonly asked ques

Q: After restoration, where will San Francisco gets is water? A: From the Tuolumne River, just as it does now. This report addresses only the most commonly asked question by restoration skeptics: Where would the water come from? Restoration would also require increased water treatment costs and replacement of about 350 gigawatt-hours per year of hydropower production – issues not addressed herein.

Sacramento River Temperature Task Group Annual Report of Activities, October 1, 2015 through September 30, 2016

Delta Stewardship Council (Delta Council) | October 31st, 2016