channelized tidal region into small volumes (represented by nodes) joined 

 together by links. Conservation of water mass is maintained throughout the 

 tidal cycle simulation by transfer of water volume between adjoining nodes in 

 the network. 



Model calibration was achieved by reproducing the tidal elevations and 

 water velocities measured in the existing Bolsa Bay region. It was found that 

 the model was most sensitive to the geometry of the water channels and wet- 

 lands basins as the water capacity varied with the tidal elevation. This 

 further reinforced the choice of the link/node model for application to this 

 project because the proposed alternatives call for major expansion of the 

 tidal wetlands acreage, and thus a significant change in tidal prism geometry. 

 Complete details of model assumptions, calibration, and study results are 

 given in Hales, et al . (in publication). 



Tidal Circulation . The calibrated numerical model was used to examine a 

 total of 12 variations of the two proposed entrance alternatives. These 

 included the navigable entrance alternative with and without a navigable 

 connecter channel between Bolsa Bay and Huntington Harbour, the non-navigable 

 entrance alternative, and four simulations where it was assumed that the non- 

 navigable channel closed due to blockage by littoral material. 



Water Quality Assessment . Existing data and information pertaining to 

 water quality characteristics of Bolsa Bay were obtained from Federal, State, 

 and Local agencies, and other organizations concerned with the water quality 

 of the Bay. Supplemental field data were collected consisting of measurements 

 of temperature, pH, conductivity, and dissolved oxygen. Sediment samples were 

 gathered and analyzed to determine contamination in the existing wetlands. 

 The link/node model was used to simulate transport of conservative tracer 

 throughout the modeled tidal region, and these results provided estimates of 

 water residence times for the existing Bolsa Bay configuration and for the 

 various proposed alternatives. Finally, a qualitative assessment of potential 

 impacts to water quality was made based on both the data analyses and the 

 numerical simulations. 



Study Elements . The bay response numerical modeling task specifically 

 examined the following elements relative to potential impacts that may result 

 from construction of a project at Bolsa Chica. 



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