3D Simulations of Flow in the Delta Cross Channel Region of the Sacramento River with Implications for Fish Passage

Estuaries are a valuable natural resource as a habitat for living creature. An evaluation of the environmental effects of an estuarine change in which the distribution and transport of estuarine salts, sediments, contaminants, and certain biological organisms (for example, plankton and larval fish) are governed by advection and dispersion usually requires an understanding of the physical processes of water circulation and mixing. Because significant variations in currents and salinity occur in all three spatial dimensions in most estuaries, 3-D models are needed. In the vicinity of Delta Cross Channel, tidal currents in estuaries that flow in opposite directions at different depths or travel in one way near a shoreline and in the opposite way near the center of a channel are not uncommon. The momentum exchanges that occur in the flow junction are severe enough to affect the longitudinal and transverse circulations and the vertical mixing. A fine grid three-dimensional semi-implicit finite deference hydrodynamic model was developed to validate hydrodynamic mechanisms and fish behaviors in the vicinity of Delta Cross Channel. For the calibration, a new 3-D numerical model results for flow, water surface elevation, and velocity profile data are compared with field studies data obtained in 2000. The results show that the a new 3D numerical model fits flow and water surface elevation data measured in the vicinity of DCC better than results of DSM2. The new 3D numerical model provides represents of three dimensional velocity profiles measured in the vicinity of DCC.