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.