Possible Effects on the Mixing of Scalars in Elkhorn Slough due to Cooling Water Pumping.

The Moss Landing harbor and estuary are characterized by a large volume of water (Q ~ 1000 m³ / min) being pumped out for use as cooling water at the adjacent Moss Landing Power Plant. Of interest was the concentration distribution of a passive scalar ( ie. fish larvae) that enters the estuary as a point source halfway between pump station and the open ocean. Due to the small freshwater inflow from the adjacent sloughs I proposed a one dimensional estuarine model where the net advective flow was determined by the pumping rate Q. The tidal velocities of the system were time averaged over longer timescales and incorporated into an effective one-dimensional dispersion coefficient, Kx. Baroclinic effects were neglected since the freshwater inflow was too small to cause significant density variations. Wind effects were also left out due to lack of data. The solution to this model predicted a larval cloud that grew with variance \sigma ² = 2 Kx t, as it was advected towards the intake pumps at a rate of U =.02m/s. I further adjusted the effective Kx to account for tidal trapping of contaminant in the "dead" arm of the harbor. Okubu's (1973) proposed Kx model for tidal trapping was implemented based on a rough estimate of trap to channel volume. This adjustment lead to a 10% increase in Kx. Currently, I am working on a one dimensional diffusion model that incorporates tidal advection and uses a finite-element numerical method to solve for the distribution and growth of the passive scalar cloud.