Delta Regional Monitoring Program Nutrients Synthesis: Modeling to Assist Identification of Temporal and Spatial Data Gaps for Nutrient Monitoring

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

Nutrient loads are an important water quality management issue in the Sacramento-San Joaquin Delta (Delta) and there is consensus that the current monitoring activities d

Nutrient loads are an important water quality management issue in the Sacramento-San Joaquin Delta (Delta) and there is consensus that the current monitoring activities do not collect all the information needed to answer important management questions.  The purpose of this report is to use hydrodynamic model outputs to refine recommendations for monitoring nutrients and related conditions in the Delta. The basic premise was that variability in water source and hydraulic residence time can serve to estimate variability in water quality. Therefore, using existing hydrodynamic models that are highly resolved in space and time could be a cost-effective way to get information about likely spatial and temporal variability in nutrients and nutrient-associated parameters. We assume that the Delta can be divided into relatively homogeneous subregions (e.g., such as those proposed in a previous report by Jabusch et al. 2016) and that a representative monitoring location can be chosen in each subregion to track status and trends. We also assume that, within any subregion, areas with long hydraulic residence time and source water mixing may represent potential nutrient transformation hotspots.  Two types of modeling approaches were applied: 1) volumetric water source analysis to evaluate the mix of source waters within each subregion; and 2) particle tracking simulations. Results from the source water analysis were evaluated to assess heterogeneity of water sources within each of the subregions. Results from the particle tracking analysis were evaluated to identify high-residence-time areas. Finally, we compared analysis results to current monitoring locations to inform potential monitoring gaps or redundancies within each of the subregions. 

Delta Salinity Management Workshops 2022 Information Sheet

Delta Stewardship Council (Delta Council) | March 7th, 2022

Delta Science Plan (2016 update)

Delta Stewardship Council (Delta Council) | May 9th, 2016

The Delta of the Sacramento and San Joaquin rivers is the hub of California’s extensive water supply system and critical to the State’s economy. However, emerging sca

The Delta of the Sacramento and San Joaquin rivers is the hub of California’s extensive water supply system and critical to the State’s economy. However, emerging scarcities of water in the Delta watersheds, which are expected to intensify with global warming, threaten California’s ability to sustain further economic development and population growth.  At the same time, patterns of water and land use have resulted in severe declines in the abundances of many valuable native species. Protecting and restoring these species while maintaining a reliable water supply and building California’s economic future is an absolute priority. The economic and environmental stakes in the Delta are enormous. Over 27 million people rely on Delta water and the ecosystem has been degraded to the point where over 60 native species are listed as threatened or endangered. The Delta and its water supply infrastructure are also highly vulnerable to earthquakes, floods, and droughts. Proposed actions under the Bay Delta Conservation Plan to reduce risks to the people, ecosystems and economy of California are likely to cost many billions of dollars. Achieving the co-goals of the Delta Plan will depend upon acquiring and communicating a new shared body of scientific knowledge to catalyze cultural change. The Delta Science Plan is intended to be that catalyst. The Delta Science Plan provides direction for achieving an integrated, collaborative and transparent science of the Delta to enhance policy and management decisions. The Plan is transformative and uses principles that have proven successful in other Big Science programs – embracing emerging technologies and fostering open science communities. The science plan uses collaboration to build trust and acquire a shared body of scientific knowledge. It proposes new mechanisms for synthesis and communication that will enhance decision-making and reduce conflicts that hinder policy decisions. Vigorous and sustained investment in the Delta Science Plan will ensure that the responsible agencies have the knowledge, trust and collaboration necessary to achieve the coequal goals.

Delta Science Plan (2019)

Delta Stewardship Council (Delta Council) | May 23rd, 2019

A coordinated, science-based approach is essential for managing the Sacramento-San Joaquin Delta (Delta) to achieve the vision of One Delta, One Science and further the

A coordinated, science-based approach is essential for managing the Sacramento-San Joaquin Delta (Delta) to achieve the vision of One Delta, One Science and further the coequal goals in a manner that enhances and protects the Delta as an evolving place. As members of the 18 federal and state agencies composing the Delta Plan Interagency Implementation Committee (DPIIC), we recognize that we must avoid a siloed, single-interest approach to management and science issues in the Delta. Such an approach hampers effective management and efficient resource use to address complex issues including increasing risks from climate change related effects such as sea level rise, prolonged dry periods, and floods. Our focus must be twofold: a more integrated effort among federal and state agencies and stakeholders to advance Delta-relevant scientific knowledge and using that knowledge to inform decisions that address these complex natural resource management issues. The Delta Science Plan is a call to action for a more collaborative Delta science community that contributes to improving decision-making in the Delta. This document provides direction for collectively prioritizing research questions, setting goals, developing shared protocols for how science is conducted, and verifying and communicating scientific results with an eye towards usability for decision-makers and the public. This direction is only possible if the Delta science community, including members of DPIIC, work together to implement and conduct work consistent with the actions identified in the document and to speak with one voice to marshal support for scientific efforts. The members of DPIIC are committed to promoting and investing in coordinated and collaborative efforts that generate scientific knowledge to support both the Delta Plan and the objectives identified in the 2009 Delta Reform Act. This commitment has been expressed through DPIIC’s endorsement and acceptance of the Interim Science Action Agenda (2014), the High-Impact Science Actions (2015), and the Science Action Agenda (2017); documents that identify and prioritize collaborative science efforts. In endorsing the Delta Science Plan, we accept the document as a shared guide to build the collaborative science community and support efforts to work together in carrying out integrated actions that achieve the vision of One Delta, One Science.

Delta smelt resiliency strategy

California Department of Water Resources (DWR) | July 11th, 2016

The Delta Smelt Resiliency Strategy (Strategy) is a science-based document that has been prepared by the State of California (State) to voluntarily address both immediate

The Delta Smelt Resiliency Strategy (Strategy) is a science-based document that has been prepared by the State of California (State) to voluntarily address both immediate and near-term needs of Delta Smelt, to promote their resiliency to drought conditions as well as future variations in habitat conditions. The Strategy relies on the MAST Report and Conceptual Models (IEP 2015) to articulate a suite of actions that can be implemented in the next few years that are intended to benefit Delta Smelt. Although the feasibility and effectiveness of each action included in the Strategy requires further exploration and study, the Strategy is an aggressive approach to implementing any actions that can be implemented in the near term, can be implemented by the State with minimal involvement of other entities, and have the potential to benefit Delta Smelt. State agencies that could implement this Strategy include Department of Water Resources (DWR), Department of Fish and Wildlife (DFW), and Division of Boating and Waterways (DBW). Several of the actions identified in this Strategy could also benefit other species, and coordination across various resource management agencies as appropriate may allow for benefits beyond Delta Smelt. All of the actions will be in compliance with applicable laws, including the Federal Endangered Species Act, California Endangered Species Act, California Environmental Quality Act, National Environmental Policy Act, and the Federal Clean Water Act. The Collaborative Science and Adaptive Management Program (CSAMP) will be used to determine the appropriate research approach to designing and assessing the outcomes of these management actions individually and synergistically. Additionally, it is expected that the Bureau of Reclamation (Reclamation) would participate in the implementation of this Strategy, including providing enhanced outflows in 2016.

Delta Smelt: Life History and Decline of a Once-Abundant Species in the San Francisco Estuary

University of California, Davis (UC Davis) | July 1st, 2016

The delta smelt is endemic to the upper San Francisco Estuary. Much of its historic habitat is no longer available and remaining habitat is increasingly unable to sustain

The delta smelt is endemic to the upper San Francisco Estuary. Much of its historic habitat is no longer available and remaining habitat is increasingly unable to sustain the population. As a listed species living in the central node of California’s water supply system, delta smelt has been the focus of a large research effort to understand causes of decline and identify ways to recover the species. Since 2008, a remarkable record of innovative research on delta smelt has been achieved, which is summarized here. Unfortunately, research has not prevented the smelt’s continued decline, which is the result of multiple, interacting factors. A major driver of decline is change to the Delta ecosystem from water exports, resulting in reduced outflows and high levels of entrainment in the large pumps of the South Delta. Invasions of alien species, encouraged by environmental change, have also played a contributing role in the decline. Severe drought effects have pushed delta smelt to record low levels in 2014–2015 and diverse and substantial management actions are needed to preserve delta smelt.

Delta Stewardship Council 2024 Annual Report

Delta Stewardship Council (Delta Council) | February 3rd, 2025

California relies on the Sacramento-San Joaquin Delta as a hub for water, biodiversity, agriculture, infrastructure, transportation, recreation, and more. Since 2010, the

California relies on the Sacramento-San Joaquin Delta as a hub for water, biodiversity, agriculture, infrastructure, transportation, recreation, and more. Since 2010, the Delta Stewardship Council has worked to advance California’s coequal goals for the Delta – a reliable statewide water supply and a resilient ecosystem – in a manner that protects and enhances the Delta’s unique character and values. In 2024, we reflected on how our agency has grown to continue facilitating collaboration with our partners.

Delta Subsidence in California: The sinking heart of the state

U.S. Geological Survey (USGS) | April 8th, 2000

The Sacramento-San Joaquin River Delta of California once was a great tidal freshwater marsh blanketed by peat and peaty alluvium. Beginning in the late 1800s, levees wer

The Sacramento-San Joaquin River Delta of California once was a great tidal freshwater marsh blanketed by peat and peaty alluvium. Beginning in the late 1800s, levees were built along the stream channels, and the land thus protected from flooding was drained, cleared, and planted. Although the Delta is now an exceptionally rich agricultural area (over a $500 million crop value in 1993), its unique value is as a source of freshwater for the rest of the State. It is the heart of a massive north-to-south water delivery system. Much of this water is pumped southward for use in the San Joaquin Valley and elsewhere in central and southern California. The leveed tracts and islands help to protect water-export facilities in the southern Delta from saltwater intrusion by displacing water and maintaining favorable freshwater gradients. However, ongoing subsidence behind the levees reduces levee stability and, thus, threatens to degrade water quality in the massive north-to-south water-transfer system.

Delta Tunnels Aren’t the “Fix” California Needs

San Francisco Baykeeper | May 24th, 2017

The Sacramento-San Joaquin River Delta is in crisis. It is not alarmist to state that the Delta-wide ecosystem—and, by extension, San Francisco Bay is in collapse and t

The Sacramento-San Joaquin River Delta is in crisis. It is not alarmist to state that the Delta-wide ecosystem—and, by extension, San Francisco Bay is in collapse and that its damaged condition may spell doom for many important species and habitats. Scientific evidence has shown that the Delta  is starving for freshwater, with repercussions for the entire estuary. While there are no quick or easy solutions to increase freshwater flows, what is clear is that the Governor’s current proposal, known as WaterFix, would authorize further water diversions from this already crippled system without first establishing a path to recovery and sustainability. WaterFix proposes to build large tunnels to take more freshwater from the Delta without substantially addressing the urgent environmental issues facing these river systems. The tunnels would harm the rivers, harm the Delta, and harm San Francisco Bay.

Delta Vision Strategic Plan

State of California | October 17th, 2008

When it was created by Governor Schwarzenegger’s Executive Order S-17-06 in 2006, the charge of the Delta Vision Blue Ribbon Task Force (Task Force) was nothing less th

When it was created by Governor Schwarzenegger’s Executive Order S-17-06 in 2006, the charge of the Delta Vision Blue Ribbon Task Force (Task Force) was nothing less than to create a vision to repair the ecological damage to the Sacramento-San Joaquin River Delta (Delta), and then prepare a strategic plan which would sustain the Delta in future decades while ensuring a reliable water supply for the two-thirds of California’s population who depend in whole or in part on water from the Delta.