Executive Summary
This report provides a project update for year two of a three-year collaboration between the San
Francisco Bay Nutrient Management Strategy (NMS), San Francisco Bay Regional Monitoring Program,
and South Bay Salt Pond Restoration Project, to estimate high frequency suspended sediment
concentration (SSC) in San Francisco Bay (SFB). Through its role in monitoring water quality in SFB, the
NMS maintains an array of autonomous sondes that record high frequency (15-minute) water column
turbidity, amongst a suite of other environmental parameters. Turbidity data from these monitoring
sites was combined with discrete SSC samples to create a bay-wide turbidity-SSC calibration, allowing
for estimates of high frequency SSC. The calibration for 7 of these sites was performed using a linear
mixed effect model (LMM), which leverages similarities in the turbidity-SSC relationship between sites
while allowing for potential differences. An additional turbidity-only sensor was deployed at an 8th site
along with discrete SSC collection, with this calibration performed via least squares linear
regression. Both models showed reasonable agreement between turbidity and SSC, with R2 = 0.62 for
the LMM, and R2 = 0.72 for the regression performed at the turbidity-only site.
Using these calibrations, we created continuous 15-min SSC datasets at all 8 locations, representing 1
channel, 4 shoal, and 3 slough sites. These calibrations are considered preliminary and will be finalized
as part of the final year 3 report after SSC sample collection is completed. For these datasets, only
turbidity data less than 110% of the maximum calibration value were converted to SSC. In total, SSC
estimates were generated for ~90-99% of the data record at the water quality monitoring sites and 68%
of the record at the turbidity-only station.
This work was funded by the South Bay Salt Pond Restoration Project, the Regional Monitoring Program
for Water Quality in San Francisco Bay, and the San Francisco Bay Nutrient Management Strategy.
Suggested citation:
Mourier, L.; Montgomery, L.; Volaric, M.; Chelsky, A.; Senn, D. 2024. Continuous Suspended Sediment
Monitoring in South and Lower South San Francisco Bay: Year Two (2023) Report. SFEI Contribution No.
1188. San Francisco Estuary Institute: Richmond, CA
