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 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 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.

Delta Vision Strategic Plan -- from Phil Isenberg, 1939-2023

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.

Delta-Mendota Subbasin Staff Assessment

California State Water Resources Control Board (SWRCB) | March 2nd, 2026

The Delta-Mendota Subbasin (subbasin) is located in the western portion of the San Joaquin Valley, in portions of Fresno, Madera, Merced, San Joaquin, San Benito, and Sta

The Delta-Mendota Subbasin (subbasin) is located in the western portion of the San Joaquin Valley, in portions of Fresno, Madera, Merced, San Joaquin, San Benito, and Stanislaus counties, and contains the cities of Dos Palos, Firebaugh, Gustine, Los Banos, Mendota, Newman, and Patterson. It is critically overdrafted and managed by 7 GSA Groups, comprised of 23 GSAs, which include: the Aliso Water District GSA Group, the Farmers Water District GSA Group, the Fresno County Management Areas A and B GSA Group, the Grassland GSA Group, the Northern Delta-Mendota GSA Group, the Central Delta-Mendota GSA Group, and the San Joaquin River Exchange Contractors GSA Group. During most years, agriculture accounts for more than 85% of groundwater use in the subbasin (Water Year 2019–Water Year 2024 Annual Reports). The state intervention process for the Delta-Mendota Subbasin was initiated in March 2023 when DWR determined the subbasin’s six 2022 GSPs were inadequate.  The GSAs released a single revised draft GSP in May 2024, which they adopted with slight revisions in July 2024 (2024 GSP). State Water Board staff evaluated the 2024 GSP to determine if identified deficiencies were resolved. The GSAs made significant progress. State Water Board staff concludes the GSAs amended the GSP such that a probationary designation of the Delta-Mendota Subbasin is unnecessary and recommends the Board return the subbasin to DWR’s jurisdiction for continued evaluation of local management under SGMA.

Demographic predictors of urinary arsenic in a low-income predominantly Hispanic pregnancy cohort in Los Angeles

Journal of Exposure Science & Environmental Epidemiology (Springer) | July 27th, 2020

Arsenic (As) is a contaminant of top public health concern, due to its range of detrimental health effects. Arsenic exposure has not been well-characterized among the US

Arsenic (As) is a contaminant of top public health concern, due to its range of detrimental health effects. Arsenic exposure has not been well-characterized among the US Hispanic populations and has been particularly understudied in this population during pregnancy. As part of the MADRES ongoing pregnancy cohort of predominantly lower-income, Hispanic women in Los Angeles, CA, we examined levels of maternal first trimester urinary As, including total As and As metabolites (inorganic (iAs), monomethylated (MMA) and dimethylated As (DMA)), in relation to participant demographics, lifestyle characteristics, and rice/seafood consumption, to identify factors that may influence As exposure and its metabolites during pregnancy (N = 241). Total As concentrations ranged from low to high (0.8–506.2 μg/L, mean: 9.0 μg/L, SD: 32.9) in our study population. Foreign-born Hispanic women had 8.6% higher %DMA (95% CI: 3.3%, 13.9%) and −7.7% lower %iAs (95% CI: −12.6%, −2.9%) than non-Hispanic women. A similar trend was observed for US-born Hispanic women. In addition, maternal age was associated with 0.4% higher %iAs (95% CI: 0.1%, 0.6%) and 0.4% lower %DMA (95% CI: −0.7%, −0.1%) per year, which may indicate poor As methylation capacity. Individual factors may predict As exposure and metabolism in pregnancy, and in turn, greater risk of adverse health effects.

Demonstration of a Watershed Approach to Wetland Restoration Planning for Load Reductions: A Pilot Demonstration Project Using GreenPlan-IT in the Santa Rosa Plain, Sonoma County, California

San Francisco Estuary Institute (SFEI) | December 30th, 2017

This summary memorandum presents technical recommendations to the 401 Certification and Waste Discharge Program (401 Program) of the State Water Resources Control Board (

This summary memorandum presents technical recommendations to the 401 Certification and Waste Discharge Program (401 Program) of the State Water Resources Control Board (State Board) for a coherent, scientifically sound, repeatable, watershed approach to wetland restoration site evaluation, compliance monitoring and assessment, and Tracking. The recommendations are drawn from the previous four memoranda produced for the Pilot Demonstration Project (Project) that address the following subjects: project work plan and information flow diagram; scientific literature review; landscape scenario planning (to map and prioritize restoration opportunities); and a framework for a watershed-approach to evaluate and report the capacity of a wetland restoration site to protect wetland beneficial uses. This Project focused on a sub-watershed of the Santa Rosa Plain, in Sonoma County, California. The area was chosen for the Project for three reasons: (1) it is integral to an existing nutrient TMDL and therefore is supported relatively well with hydrological and nutrient data; (2) the historical and existing wetlands and streams of the area were mapped recently in sufficient detail to inform landscape planning; and (3) implementation of the TMDL will involve wetland restoration to reduce downstream nutrient loads, and therefore the Project may help implement the TMDL. The primary overall purpose of this Project was to explore how numerical simulation and statistical modeling could be combined with existing wetland assessment and reporting tools to create a coherent, watershed-based approach to wetland beneficial use protection. Any relevance to the existing nutrient TMDL for the demonstration area is an intentional, but secondary benefit of this Project. Contents: Wetland Beneficial Use Protection: Pilot Demonstration Project A Synthesis of Literature on Wetland Assimilation Capacities, Models, and Pollutant Loads Simulating Wetland Assimilation Capacity in the Lower Santa Rosa Creek Watershed Pilot Demonstration Area Using the HSPF Model Demonstration of a Watershed Approach To Wetland Restoration Planning Using GreenPlan-IT

Department of Fish and Game Rationale for Effects of Exports

California Department of Fish and Wildlife (CDFW) | November 2nd, 2011

This document describes the California Department of Fish and Game (DFG) methodology to quantify the surface area in the Sacramento – San Joaquin delta estuary (Delta)

This document describes the California Department of Fish and Game (DFG) methodology to quantify the surface area in the Sacramento – San Joaquin delta estuary (Delta) that is impacted by the operations of the State Water Project (SWP) and Central Valley Project (CVP) pumping facilities. In order to estimate the mitigation required to offset direct and indirect losses of Fish Species due to impacts to surface acres of aquatic habitat in the Delta accounted to the SWP Delta Pumping Facilities operations, DFG used an analysis based on conclusions and information contained in a manuscript that utilizes the Delta Simulation Model-2 Particle Tracking Model (DSM2PTM) (Kimmerer and Nobriga, 2008). This methodology provides the general loss of “particles” to the Delta which is a surrogate for loss of productivity and fish life stages vulnerable to these effects.

Department of the Interior Nature-Based Solutions Roadmap

Nicholas Institute for Energy, Environment & Sustainability (Duke University) | December 1st, 2023