Nutrient Dynamics of the Delta: Effects on Primary Producers

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

Increasing clarity of Delta waters, the emergence of harmful algal blooms, the growth of aquatic water weeds, and the altered food web of the Delta have recently brought

Increasing clarity of Delta waters, the emergence of harmful algal blooms, the growth of aquatic water weeds, and the altered food web of the Delta have recently brought nutrient dynamics to the forefront. This paper focuses on the sources of nutrients, the transformation and uptake of nutrients, and the links of nutrients to primary producers. The largest loads of nutrients to the Delta come from the Sacramento River with the San Joaquin River seasonally important, especially in the summer. Light regime, grazing pressure, and nutrient availability influence rates of primary production at different times and locations within the Delta. Modern sensor technology and networks are now deployed that make high frequency measurements of nitrate, ammonium, and phosphate. Data from such instruments allow a much more detailed assessment of the spatial and temporal dynamics of nutrients. Four fruitful directions for future research include utilizing continuous sensor data to estimate rates of primary production and ecosystem respiration, linking models of the Delta with the transport and fate of dissolved nutrients, studying nutrient dynamics in various habitat types, and exploring the use of stable isotopes to trace the movement and fate of effluent-derived nutrients.

Nutrient Fluxes from Sediments in the San Francisco Bay Delta

Estuaries and Coasts (Springer) | January 1st, 2014

In September 2011 and March 2012, benthic nutrient fluxes were measured in the San Francisco Bay Delta, across a gradient from above the confluence of the Sacramento and

In September 2011 and March 2012, benthic nutrient fluxes were measured in the San Francisco Bay Delta, across a gradient from above the confluence of the Sacramento and San Joaquin Rivers to Suisun Bay. Dark and illuminated core incubation techniques were used to mea- sure rates of denitrification, nutrient fluxes (phosphate, ammonium, nitrate), and oxygen fluxes. While benthic nutrient fluxes have been assessed at several sites in northern San Francisco Bay, such data across a Delta–Bay transect have not previously been determined. Average September rates of DIN (nitrate, nitrite, ammonium) flux were net positive across all sites, while March DIN flux indicated net uptake of DIN at some sites. Denitrification rates based on the N2/Ar ratio approach were between 0.6 and 1.0 mmol m−2 day−1, similar to other mesotrophic estuarine sediments. Coupled nitrifica- tion–denitrification was the dominant denitrification pathway in September, with higher overlying water nitrate concentra- tions in March resulting in denitrification driven by nitrate flux into the sediments. Estimated benthic microalgal productivity was variable and surprisingly high in Delta sediments and may represent a major source of labile carbon to this ecosystem. Variable N/P stoichiometry was observed in these sediments, with deviations from Redfield driven by processes such as denitrification, variable light/dark uptake of nutrients by microalgae, and adsorption of soluble reactive phosphorus.

Nutrient Management Strategy Science Plan Report

San Francisco Estuary Institute (SFEI) | September 9th, 2016

The San Francisco Bay (SFB) estuary receives large inputs of the nutrients nitrogen and phosphorous from anthropogenic sources, and has the potential to suffer negative

The San Francisco Bay (SFB) estuary receives large inputs of the nutrients nitrogen and phosphorous from anthropogenic sources, and has the potential to suffer negative impacts from nutrient overenrichment. Nutrient concentrations in SFB exceed those in other estuarine ecosystems where degradation is strongly expressed. To date, SFB has shown resistance to some of the classic symptoms of nutrient over-enrichment, such as excessive phytoplankton biomass as chlorophyll-a (chl-a) and low dissolved oxygen (DO). Recent observations, however, suggest that SFB’s resistance to nutrient enrichment is weakening, and have generated concern that SFB may be trending toward, or may already be experiencing, adverse impacts due to its high nutrient loads. In response to these concerns, the San Francisco Bay Regional Water Quality Control Board (SFBRWQCB) worked collaboratively with stakeholders to develop the San Francisco Bay Nutrient Management Strategy (NMS).1 The NMS lays out an overall approach for developing the underlying science to support nutrient management decisions. This report presents a Draft Science Plan for implementing the SFB NMS. The report’s main goals include: Lay out a multi-year Science Plan representing a logical sequence of studies to inform major management decisions, assuming a time-line of 10+ years. Develop an approach and rationale for sequencing and prioritizing among studies, and identify specific high-priority studies, in particular those that should proceed in FY2016- 2018. Provide realistic estimates of the time-frame and funding needed to support a Science Plan that will successfully inform management decisions. The Draft Science Plan was developed in 2014-15 with input from science advisors (Table 1.1), the NMS Steering Committee, and the NMS Nutrient Technical Work Group (Fig. 1.1). Projects are described in more detail in the first 1-3 years, and in increasingly less detail over time, recognizing that the Science Plan will be iteratively refined based on new insights gained as work progresses.

Nutrient Management Strategy Science Program

San Francisco Estuary Institute (SFEI) | September 1st, 2017

San Francisco Bay (SFB) receives large inputs of the nutrients nitrogen (N) and phosphorous (P) from anthropogenic sources. N and P are essential components of a healthy

San Francisco Bay (SFB) receives large inputs of the nutrients nitrogen (N) and phosphorous (P) from anthropogenic sources. N and P are essential components of a healthy estuary, supporting primary production at the base of the food web. However, ambient N and P concentrations in SFB exceed those in many other estuarine ecosystems, including those considered eutrophic1 and that experience nutrient-related impairment, such as excessive phytoplankton blooms and prolonged periods of low dissolved oxygen (DO). Unlike those other nutrient-enriched estuaries, though, SFB has exhibited resistance to classic eutrophication symptoms. Recent observations, however, suggest that SFB’s resistance to nutrient enrichment is weakening (e.g., Cloern et al., 2007; Cloern et al., 2010; SFEI 2014a).  These San Francisco Bay Nutrient Management Strategy (NMS) Science Program was launched in 2014 to develop the scientific foundation to support nutrient management decisions. The NMS Steering Committee, representing 13 stakeholder groups (regulators, dischargers, water purveyors, NGOs, resource agencies) oversees the NMS’ implementation, including financial oversight and alignment of NMS science activities with high priority management questions. The San Francisco Estuary Institute (SFEI) serves as the technical lead on implementing the NMS Science Program. SFEI staff work with regional collaborators to carry out NMS projects, including field investigations, monitoring, and data interpretation. 

Observational Study of Sycamore Regeneration at two sites in Santa Clara County after the 2016-2017 Water Year

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

This memo serves as an update to the Sycamore Alluvial Woodland Habitat Mapping and Regeneration Study (Beagle et al. 2017), and describes changes seen at the two study s

This memo serves as an update to the Sycamore Alluvial Woodland Habitat Mapping and Regeneration Study (Beagle et al. 2017), and describes changes seen at the two study sites, Upper Coyote Creek and Pacheco Creek, between fall 2015 and fall 2017. We were tasked with augmenting tree core data as reported in 2017 by adding additional trees to further investigate the relationship between sycamore establishment and geomorphic position, which partially serves as a proxy for the role flood processes play in improving the suitability of conditions for sycamore seedling establishment and growth. Coincidentally, major flooding during water year 2016-2017 provided us with an exciting opportunity to observe sycamore regeneration at these two study sites. This memo reports on tree coring results; documents and maps sycamore seedlings and other observed regeneration strategies of sycamores during 2018 related to geomorphic change at the two study sites; proposes natural and anthropogenic drivers of sycamore regeneration; and outlines next steps for further investigation. 

Old and Middle River Flow Review: USGS Gauge Readings versus Index Calculations for 2011 through 2017

California Department of Water Resources (DWR) | November 17th, 2017

This report will demonstrate the strong flow correlation between the United States Geological Survey gages at the Old and Middle Rivers (USGS OMR), and the OMR Index calc

This report will demonstrate the strong flow correlation between the United States Geological Survey gages at the Old and Middle Rivers (USGS OMR), and the OMR Index calculations, which have been used by the State Water Project and the Central Valley Project (the Projects) to operate to, and comply with, Old and Middle River (OMR) flow requirements. The results of the two different methodologies for determining OMR will be compared with daily, 5-day average, and 14-day average values, and will demonstrate a close correlation and tracking between the two methodologies. The time-span will be from December to June of the Water Years 2011 to 2017 and gives a background view and general effectiveness of using the OMR Index. The difference between the methodologies is that the USGS OMR values are based on tidally filtered hourly flow values of Old and Middle Rivers near Bacon Island, whereas the Index methodology uses an empirical equation based on net flows into and out of the Southern Delta. The USGS OMR flow values have been difficult for the Projects to operate to, in large part because the tidally filtering calculation is lagged by three days. What’s more, atmospheric conditions exert an unpredictable influence on OMR values and missing data introduces errors. By contrast, the OMR Index is much easier to work with because the San Joaquin River at Vernalis (VNS) gage used in the OMR Index equation is located upstream of the Delta and is therefore not affected significantly by tidal effects or atmospheric conditions and has only a one-day delay in the OMR Index equation. Using prior day flows from the VNS gage allows the Projects’ operations to be more predictable since current day exports can be closely controlled. Through regression analysis and empirical graphs, this report will show that the OMR Index method produces results that are closely correlated with values from the USGS OMR. And since the Index method can be used to closely approximate the USGS OMR flow values over an averaging period, the Index method is a satisfactory alternative to using the lagged USGS OMR flow data for real-time operations.

Oppose the Twin Tunnels Project: A C-­WIN Policy Brief

California Water Impact Network (C-WIN) | October 1st, 2012

It is the policy of the California Water Impact Network to: • Oppose and work to defeat the construction of the Twin Tunnels Project which would divert water from th

It is the policy of the California Water Impact Network to: • Oppose and work to defeat the construction of the Twin Tunnels Project which would divert water from the Sacramento River to the South Delta pumps before it gets to the Bay-­Delta. • Support and work to achieve the reduction in Delta exports to a maximum of 3 million acre-­feet per year.  Oppose any increased Delta exports to Central and Southern California. • Support and work to achieve the elimination of paper water from State Water Project and Central Valley Project contracts. • Support regional water self-­sufficiency through conservation, recycling, storm water capture and other “soft path” means. • Support upgrading Delta levees to withstand both sea level rise and the risk of a major earthquake. •  Support increased water supply reliability for State Water Project urban areas by reinstatement of the Urban Water Preference in State Water contracts and returning the Kern Water Bank to the public to store the Urban Preference south of the Delta as a drought supply.

Optimizing sampling methods for monitoring pollutant trends in San Francisco Bay urban stormwater

San Francisco Estuary Institute (SFEI) | July 1st, 2016

The Small Tributaries Loading Strategy (STLS) focuses on urban stormwater loadings from small tributaries. To date, STLS monitoring has been geared towards dete

The Small Tributaries Loading Strategy (STLS) focuses on urban stormwater loadings from small tributaries. To date, STLS monitoring has been geared towards determining concentrations and annual loads of PCBs and Hg; the sampling approach has yet to be fully optimized for detecting trends over time. Here, we evaluate the variability and statistical power for detecting future trends in PCBs based on baseline STLS data in the Guadalupe River watershed. The objective was to improve our understanding of the influence of climatic and seasonal factors on baseline stormwater pollutant conditions, and inform refinements to the STLS monitoring design for detecting trends.

Order Approving Temporary Urgency Changes to Water Right License and Permit Terms Relating to Delta Water Quality Objectives

California State Water Resources Control Board (SWRCB) | February 21st, 2023

Our Vision for the California Delta

Delta Vision Blue Ribbon Task Force (Delta Vision) | March 19th, 2008