Report on Salton Sea Projects

California Natural Resources Agency (CNRA) | April 8th, 2016

Formed in 1905 when Colorado River flood waters breached an irrigation diversion structure and caused the river to temporarily flow into the then-dry Salton Sink, today�

Formed in 1905 when Colorado River flood waters breached an irrigation diversion structure and caused the river to temporarily flow into the then-dry Salton Sink, today’s Salton Sea is only the latest in a long succession of waterbodies to occupy the area. At 350 square miles, California’s largest lake is hydrologically connected to the Colorado River system and has been largely maintained since the 1905 event by irrigation water from agricultural production in the Imperial Valley. The historic Quantification Settlement Agreement (2003) provided California the means to implement water transfers and supply programs that allowed the state to live within its 4.4 million acre-foot basic annual apportionment of Colorado River water. Though long plagued by problems associated with its terminality—and resultant accumulation of salts, nutrients, and other impurities—the water transfers contained in the QSA meant a hastening of its ecological decline. Mitigation waters were provided for the Sea in the agreement, but are set to expire in 2017.  In response to growing concern about the impending and current deterioration of conditions at the Salton Sea, California Governor Edmund G. Brown Jr. in May 2015 created the Salton Sea Task Force to rapidly evaluate and take action to bring certainty to the Sea’s future and develop a series of findings that would guide further action at the lake. To coordinate and facilitate the actions the Governor also created the position of Assistant Secretary for Salton Sea Policy within the California Natural Resources Agency (CNRA).  The Salton Sea Task Force issued their findings in November 2015, which called for the development of a Salton Sea Management Program that covered three major elements: sustainable habitat; air quality and potential private sector energy development. The Task Force also acknowledged that a successful program depends on the following three principles: 1) strong state, federal, and local partnerships; 2) clear and achievable milestones with state directed plans to achieve them; and 3) committed participation from all stakeholders who share the goals of protecting air quality, reducing habitat impacts, and maintaining a secure Colorado River Water Supply. Task Force findings also contained a series of actions for implementation by the California Natural Resources Agency (CNRA) that included the development of a Salton Sea Management Plan with short and midterm goals for habitat and dust suppression projects, an improved public awareness and local partnerships program and an accelerated implementation of planning, permitting and construction. 

Response to the Delta Science Program and Independent Review Panel Report from the 2015 Annual Review of the Long-term Operation Biological Opinions (2015 Annual Review) (January 29, 2016)

Delta Stewardship Council (Delta Council) | January 29th, 2016

Restoration pulse flows from a California dam temporarily increase drifting invertebrate biomass concentration

Journal of Environmental Management (Elsevier) | November 9th, 2022

The decline of Pacific salmon (Oncorhynchus spp.) populations over the last few decades has stimulated major restoration efforts across the Pacific Northwest to improve t

The decline of Pacific salmon (Oncorhynchus spp.) populations over the last few decades has stimulated major restoration efforts across the Pacific Northwest to improve the status of these iconic fishes. The leading factors contributing to the decline of Pacific salmon include watershed degradation and water diversions, which result in part from widespread dam construction across the United States (Moyle, 1994). Early river restoration actions primarily focused on physical habitat alterations (e.g., in-stream habitat improvement, fish passage; Barinaga, 1996; Bernhardt et al., 2005), while more recent work has centered around restoring natural processes (Johnson et al., 2019). Since socioeconomic and political complications are typically too great for dam removal projects to be feasible, reconciliation ecology, which encourages the accommodation of both human and wildlife needs in a human-dominated landscape, can be a more effective approach to restoration (Rosenzweig, 2003; Moyle et al., 2017). Rather than the elusive goal of returning rivers to a natural flow regime, the aim can be to attain functional environmental flows to support beneficial flow-ecology relationships (Poff et al., 2017). Dams can be operated to reduce some of their detrimental effects by releasing flows that improve downstream habitat through the preservation of key hydrologic signals upon which biophysical processes and native biological communities depend (Yarnell et al., 2020). Four functional flow components were identified for Mediterranean montane streams: wet-season initiation flows, peak magnitude flows, spring recession flows, and dry-season low flows; see Yarnell et al. (2015) for a description about the importance of each key functional component. Several studies have identified the need to further assess linkages between streamflow, invertebrate prey availability, and drift-foraging dynamics for consideration in future restoration plans for juvenile salmonids (Weber et al., 2014; Naman et al., 2016; Lusardi et al., 2018). The focus of this study is to assess the impact of dam-release flows imitating one of those functional flow components, peak magnitude flows, on invertebrate drift as a food resource for juvenile salmonids.

Review of CDFW Recommendations for the 2022 Readoption of Drought Emergency Regulations on the Scott River and Recommendations for Future Management During Extreme Drought Conditions

Siskiyou Farm Bureau | August 31st, 2022

Review of North Delta Salmon Out-Migration Study

CALFED | January 23rd, 2008

This document is a review of the North Delta Salmon Out-Migration Study (NDSOS) proposed to the California Department of Water Resources (DWR) by a group of PIs l

This document is a review of the North Delta Salmon Out-Migration Study (NDSOS) proposed to the California Department of Water Resources (DWR) by a group of PIs lead by Jon Burau of the USGS. To carry out this review, the CALFED Science program, acting at the request of DWR and the PIs, convened a panel that was given a substantial written proposal describing the study. In addition to the written proposal, the PIs gave a series of presentations to a majority of the panel members at a public workshop held on January 10, 2008. The presentations provided many details about the proposed study that were not included in the written proposal. The panel was charged by CALFED to: “.... make recommendations concerning, and oversee incorporation of modifications to, the proposed study to ensure that, when funded, executed, and analyzed, the proposed investigation will provide the best-available science when characterizing the hydrodynamics and movement of out-migrating salmon smolts in the north Delta region in response to several alternate regional configurations.” This report is the panel’s response to that charge. In the sections that follow, we start by describing those aspects of the proposal that the panel found would work well or were strong positives. We follow this with a critique of perceived shortcomings of the proposal and a set of recommendations for possible changes to the proposed work that would improve the proposed study. These recommendations were based on the information in the written proposal provided to the panel and on the presentations made at the public workshop.

Review of the Long-Term Operations of the Central Valley Project and the State Water Project

National Academy of Sciences (NAS) | November 10th, 2025

The CVP and SWP (referred to collectively as “the Projects”) rarely deliver their full contracted  amount of water. Some of this is inherent in the operation of larg

The CVP and SWP (referred to collectively as “the Projects”) rarely deliver their full contracted  amount of water. Some of this is inherent in the operation of large water projects with diverse demands in a dry and highly variable climate. A growing, complex regulatory environment of state and federal laws, some of which were created to protect fish species endemic to the Delta, has further restricted CVP and SWP operations.  These fish include the southern distinct population segment of North American green sturgeon, California Central Valley steelhead, Central Valley spring-run Chinook salmon, Sacramento River winter-run Chinook salmon, longfin smelt, and Delta smelt. Operating the Projects while trying to prevent species extinction can be a source of conflict if the actions to prevent extinction reduce the amount of water that can be exported. Project operation into the future will likely become more challenging as changes in various climatic factors push the listed species closer to their thresholds of survivability. Hence, in late 2023 USBR contracted with the National Academies of Sciences, Engineering, and Medicine (NASEM) to form an expert committee that could serve as an independent review for the CVP and SWP as they operate into the future. The Committee’s statement of task appears in Box S-1. The three actions chosen for the study—the Shasta Coldwater Pool Management Action, the Old and Middle River Flow Management Action, and the Summer-Fall Habitat Action for Delta Smelt— are perceived as consequential for species survival and controversial for their effects on water deliveries to contractors.

Revised Water Right Decision 1641

California State Water Resources Control Board (SWRCB) | December 29th, 1999

Risks of ocean acidification in the California Current food web and fisheries: ecosystem model projections

Wiley | January 12th, 2017

The benefits and ecosystem services that humans derive from the oceans are threatened by numerous global change stressors, one of which is ocean acidification. Here, we d

The benefits and ecosystem services that humans derive from the oceans are threatened by numerous global change stressors, one of which is ocean acidification. Here, we describe the effects of ocean acidification on an upwelling system that already experiences inherently low pH conditions, the California Current. We used an end‐to‐end ecosystem model (Atlantis), forced by downscaled global climate models and informed by a meta‐analysis of the pH sensitivities of local taxa, to investigate the direct and indirect effects of future pH on biomass and fisheries revenues. Our model projects a 0.2‐unit drop in pH during the summer upwelling season from 2013 to 2063, which results in wide‐ranging magnitudes of effects across guilds and functional groups. The most dramatic direct effects of future pH may be expected on epibenthic invertebrates (crabs, shrimps, benthic grazers, benthic detritivores, bivalves), and strong indirect effects expected on some demersal fish, sharks, and epibenthic invertebrates (Dungeness crab) because they consume species known to be sensitive to changing pH. The model's pelagic community, including marine mammals and seabirds, was much less influenced by future pH. Some functional groups were less affected to changing pH in the model than might be expected from experimental studies in the empirical literature due to high population productivity (e.g., copepods, pteropods). Model results suggest strong effects of reduced pH on nearshore state‐managed invertebrate fisheries, but modest effects on the groundfish fishery because individual groundfish species exhibited diverse responses to changing pH. Our results provide a set of projections that generally support and build upon previous findings and set the stage for hypotheses to guide future modeling and experimental analysis on the effects of OA on marine ecosystems and fisheries.

River-Aquifer Interactions, Geologic Heterogeneity, and Low-Flow Management

U.S. Geological Survey (USGS) | ?

Low river flows are commonly controlled by river-aquifer exchange, the magnitude of which is governed by hydraulic properties of both aquifer and aquitard mater

Low river flows are commonly controlled by river-aquifer exchange, the magnitude of which is governed by hydraulic properties of both aquifer and aquitard materials beneath the river. Low flows are often important ecologically. Numerical simulations were used to assess how textural heterogeneity of an alluvial system influences river seepage and low flows. The Cosumnes River in California was used as a test case. Declining fall flows in the Cosumnes River have threatened Chinook salmon runs. A ground water–surface water model for the lower river basin was developed, which incorporates detailed geostatistical simulations of aquifer heterogeneity. Six different realizations of heterogeneity and a homogenous model were run for a 3-year period. Net annual seepage from the river was found to be similar among the models. However, spatial distribution of seepage along the channel, water table configuration and the level of local connection, and disconnection between the river and aquifer showed strong variations among the different heterogeneous models. Most importantly, the heterogeneous models suggest that river seepage losses can be reduced by local reconnections, even when the regional water table remains well below the riverbed. The percentage of river channel responsible for 50% of total river seepage ranged from 10% to 26% in the heterogeneous models as opposed to 23% in the homogeneous model. Differences in seepage between the models resulted in up to 13 d difference in the number of days the river was open for salmon migration during the critical fall months in one given year.

Rivers that Depend on Aquifers: Drafting SGMA Groundwater Plans with Fisheries in Mind

Golden Gate University (GSU) | April 12th, 2018

In California, surface waters have historically been regulated as if they were unconnected to groundwater. Yet, in reality, surface waters and groundwater are often hydro

In California, surface waters have historically been regulated as if they were unconnected to groundwater. Yet, in reality, surface waters and groundwater are often hydrologically connected. Many of the rivers that support fisheries such as salmon and trout are hydrologically dependent on tributary groundwater to maintain instream flow. This means that when there is intensive pumping of tributary groundwater the result can be reductions in instream flow and damage to fisheries. For this reason, stakeholders concerned about adequate instream flows for fisheries in California’s rivers, streams and creeks need to be effectively engaged in the implementation of California’s Sustainable Groundwater Management Act (SGMA). Consider the Scott River in Northern California, part of the larger Klamath River Basin. Nearby groundwater contributes to the Scott River. When high volumes of groundwater are extracted from nearby wells, it depletes the Scott River’s instream flow with adverse impacts on salmon and steelhead trout. As discussed further in Section VI of this guidebook, this has led to litigation over the application of California public trust law to groundwater extraction affecting Scott River instream flows, and efforts to use SGMA to ensure that groundwater pumping near the Scott River is compatible with the instream flow needs of fisheries. Situations similar to the Scott River surface and groundwater basin are unfolding throughout California. On a statewide basis, how pervasive is the effect of groundwater pumping on surface water flows? Research by Maurice Hall of the Environmental Defense Fund, utilizing the California Department of Water Resources Central Valley Groundwater Surface Flow Model, provides us with some sense of the magnitude of the problem. In a May 2018 presentation, Hall reported: What the model showed us is that early in the 1900s, 1940s and 1950s, the Sacramento River received a net inflow from the groundwater of something like 1 million acre feet a year…Since that time, the groundwater levels have gone down, and the amount of water that has flowed into the Sacramento River from the surrounding groundwater has gone down accordingly to the point that when we were doing this modeling around 2010, it appeared that on average, the Sacramento River lost just about as much as it gained from the surrounding groundwater in the valley floor. This is the Sacramento River and all of its tributaries upstream of the Sacramento…So the net effect over that period is there was roughly on average 900,000 acre-feet per year less water showing up in the  Sacramento River at Sacramento.” (Hall and O’Brien). SGMA was enacted in 2014. Pursuant to SGMA, by June 2017 a groundwater sustainability agency was required to be designated for each groundwater basin in California. Each groundwater sustainability agency in high and medium priority basins must prepare and adopt a Groundwater Sustainability Plan (SGMA Groundwater Plan) by 2020 if the basin is deemed to be in a critical state of overdraft or 2022 for all remaining high and medium priority basins. Each SGMA Groundwater Plan must detail how the groundwater basin will be managed to avoid overdraft conditions and, importantly for fisheries, to avoid adverse impacts on hydrologically connected surface waters. Although groundwater sustainability agencies and fishery stakeholders recognize that the groundwater-surface water connection needs to be addressed in SGMA Groundwater Plans, at present there is limited guidance on how to do this. That is, what are the specific types of information, modeling, monitoring, and pumping provisions that should be included in SGMA Groundwater Plans to ensure that groundwater extraction does not cause significant adverse impacts on fisheries? The purpose of this guidebook is to provide such guidance.