Sacramento River Nutrient Change Study 2019

Photo Gallery
Map of the stations and transects sampled for the Sacramento River Nutrient Change StudyCrew from Regional San, Applied Marine Sciences, Inc., and US Geological Survey onboard Regional San vessel “Guardian” and USGS vessel “Mudslinger.” (Photo: Tamara Kraus, USGS)Crew from Regional San, Applied Marine Sciences, Inc., and San Francisco State University onboard Regional San vessel “Guardian.” (Photo: Tamara Kraus, USGS)Crew from Regional San, Applied Marine Sciences, Inc., and San Francisco State University onboard the SFSU vessel “Twin Vee.” (Photo: Lisa Thompson)Sharon Merker (Regional San – Wastewater Source Control Section) with a haul of clams from the Sacramento River. (Photo: Lisa Thompson)Water quality mapping system onboard the Regional San vessel “Guardian.” (Photo: Tim Mussen)Mokelumne River (connector between New Hope Landing and Miller’s Ferry). (Photo: Tim Mussen)US Geological Survey vessel “Landsteiner” conducting a high-frequency water quality mapping run. (Photo: Tim Mussen)Tim Mussen operating the high-frequency water quality mapping system onboard the Regional San vessel “Guardian.” (Photo: Lisa Thompson)Tim Mussen and James Noss with high-frequency water quality mapping system onboard the Regional San vessel “Guardian.” Photo: Lisa Thompson)

Regional San staff and collaborators are studying the potential environmental effects of a change in nutrient loading to the Sacramento River in September 2019, which resulted from a wastewater hold at the Sacramento River Wastewater Treatment Plant (SRWTP). This hold, which was planned as part of the EchoWater Project construction process, prevented treated wastewater from entering the Sacramento River for 48 hours. Given the relatively high river flows in 2019, the hold created a zone of wastewater-free river water over 20 miles long in the lower Sacramento River. The wastewater-free zone also stretched into nearby channels with differing water flows and turbidity, including Georgiana Slough, the North Fork Mokelumne River, and the South Fork Mokelumne River. Scientists used a small fleet of four research boats to collect water samples in all these river regions before and during the wastewater hold.

Sampling included:

  • Hydrodynamic (Water Flow) Modeling (Resource Management Associates)
  • High Frequency Water Quality Boat Mapping (US Geological Survey)
  • Water Quality Sampling and Laboratory Analysis (Regional San)
  • Plankton Enumerations (BSA Environmental Services, Inc.)
  • Phytoplankton Carbon Uptake (to determine growth rates) (Applied Marine Sciences, Inc.)
  • Zooplankton Growth (San Francisco State University)
  • Clam Collection and Analysis (Regional San and Applied Marine Sciences, Inc.)

Data and hydrodynamic modeling will be used to evaluate how phytoplankton (small aquatic plants) and zooplankton (tiny aquatic animals) responded to changes in physical and biological factors during the study. These factors include differences in nutrient loads and forms, water residence times, light levels, turbidity, and grazing by zooplankton and clams. It is important to understand the conditions regulating phytoplankton and zooplankton growth in the watershed because these organisms are a primary food source to the Delta’s ecosystem.

This study is jointly funded by the Delta Regional Monitoring Program, State Water Contractors, and US Bureau of Reclamation, with in-kind contributions from Regional San and the US Geological Survey.

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