Modeled daily Yolo Bypass inundation

Hydrology is one of the major disturbance regimes thought to shape aquatic habitat.
However, the San Francisco Estuary (SFE) has been altered by urban and agricultural
development. Approximately 95% of the estuary’s wetlands have been diked, channelization is
pervasive, and the biological community and water quality have been changed by exotic species
introductions, sediment inputs from mining, and pollution from agricultural and urban
chemicals. The hydrography has also been altered by upstream dams, which reduce the magnitude
of both winter precipitation pulses and spring snow melt pulses when filling reservoirs. In
addition to reservoir storage, 35% to 65% of tributary inflow is diverted by large water
diversions, as well as thousands of smaller agricultural pumps and siphons. Nevertheless, the
SFE retains a substantial area of seasonal off-channel habitat in the Sacramento River, the
Yolo Bypass. The Yolo Bypass is hydraulically dynamic and is strongly influenced by tides
during low discharge periods and dominated by fluvial river dynamics during flood events. This
river floodplain-tidal slough complex is, therefore, much more hydrodynamically variable than
the adjacent mainstem Sacramento River channel and benefits from additional metrics than those
typically measured for river systems. These data are the modeled duration of inundation in the
Yolo Bypass, which was approximated as the number of days in which Yolo Bypass flow was
greater than 113.27 m3/s following an inundation event from the Sacramento River (e.g., when
the stage height of the Sacramento River exceeded the height of the Fremont Weir, 10.2
meters). Inundation in the Yolo Bypass creates a complex transition zone between the river
floodplain and tidal slough habitat, which likely represents the historically dominant habitat
in the North Delta. Therefore, inundation brings many advantages for native fish, such as
increased growth opportunities on the floodplain, an alternative route into the estuary, and
an expansion and diversification of rearing habitat. This definition for inundation duration
was developed in Goertler et al. 2017.