Abstract
This paper, part of the collection of research comprising the State of Bay–Delta Science 2016, describes advances during the past decade in understanding flow dynamics and how water-quality constituents move within California’s Sacramento–San Joaquin River Delta (Delta). Water-quality constituents include salinity, heat, oxygen, nutrients, contaminants, organic particles, and inorganic particles. These constituents are affected by water diversions and other human manipulations of flow, and they greatly affect the quantity and quality of benthic, pelagic, and intertidal habitat in the Delta. The Pacific Ocean, the Central Valley watershed, human intervention, the atmosphere, and internal biogeochemical processes are all drivers of flow and transport in the Delta. These drivers provide a conceptual framework for presenting recent findings. The tremendous expansion of acoustic and optical instruments deployed in the Delta over the past decade has greatly improved our understanding of how tidal variability affects flow and transport. Sediment is increasingly viewed as a diminishing resource needed to sustain pelagic habitat and tidal marsh, especially as sea level rises. Connections among the watershed, Delta, and San Francisco Bay that have been quantified recently highlight that a landscape view of this system is needed, rather than consideration of each region in isolation. We discuss interactions of multiple drivers and information gaps.
Highlights
Movement of water and constituents carried by water within the Sacramento–San Joaquin River Delta (Delta) depend on forcing from the Pacific Ocean, the Central Valley watershed, human intervention, the atmosphere, and internal biogeochemical processes
More than 84% of the scenarios resulted in sustainable marshes with a moderate 88 cm of sea level rise (SLR) by 2100, but only 32% and 11% of the scenarios resulted in surviving marshes when SLR was increased to 133 cm and an upper bound of 179 cm, respectively
We have summarized the state of the science for flow and transport by the primary drivers: ocean, fluvial, anthropogenic, atmospheric, and biogeochemical (Figure 1)
Summary
Movement of water and constituents carried by water within the Sacramento–San Joaquin River Delta (Delta) depend on forcing from the Pacific Ocean, the Central Valley watershed, human intervention, the atmosphere, and internal biogeochemical processes. This slow advection of sediment southward, which increases turbidity in the south Delta, has important implications because elevated turbidity in the region of the pumping facilities has been linked to high entrainment of Delta Smelt at the facilities (Grimaldo et al 2009), which can lead to curtailments of federal and state water deliveries Both observations (Gleichauf et al 2014) and numerical modeling of the Delta (Monsen et al.2007) show that gate operations significantly affect hydrodynamics and transport patterns in the Delta. Supply (Wright and Schoellhamer 2004) using SSC data immediately upstream from the Delta. Hestir et al (2016) estimate that 21% to 70% of the total declining turbidity trend results from SAV expansion
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