Tidal Hydrodynamic and Salinity Models for Corpus Christi and Aransas Bays, Texas
Brandes, R. J.
Masch, F. D.
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Mathematical simulation models for tidal hydrodynamics and salinity (TDS) have been developed for the combined Corpus Christi and Aransas-Copano Bay systems. These models have been calibrated and verified to the extent possible with data collected up through mid-1971 in the TWDB/USGS data-collection program in these two bays. Additional calibration of the models was facilitated through data collected simultaneously in both bays during a comprehensive sampling run covering the period, November 5-10, 1971. In compiling the several data packages used (including the comprehensive run), supplemental information from other public and private organizations have been used where available. The simulation capabilities developed for Corpus Christi and Aransas-Copano Bays involve two compatible numerical models, one for tidal hydrodynamics and the other for salinity measured as TDS. The tidal hydrodynamic model uses an explicit numerical solution of the basic equations of motion and continuity whereas the salinity model uses an alternating-direction implicit solution to solve the mass conservation equation written for TDS. Both models utilize a rectangular grid for discretization of the combined bay systems with a mesh spacing of one square nautical mile. Basic input to the tidal hydrodynamic model includes the physiographic details of the bay system, msl depths, Manning roughness coefficients, wind conditions, magnitude and location of inflows, diversions and return flows, direct precipitation, evaporation and Gulf exciting tides. The basic outputs from this model are the temporal variations of tidal amplitudes and flows per unit width in each of two coordinate (area-wise) direction for every computational cell in the combined bay systems. The instantaneous component flows are then integrated over successive tidal cycles to determine the net advective flows in each coordinate system. The salinity model is solved under the same computational grid used for tidal hydrodynamics. Its basic input includes source salinities (TDS), the net advective flows for each cell computed with the tidal model, dispersion coefficients for each cell, and evaporation or precipitation. The basic output is the concentration of salinity or TDS in each cell for a given set of inputs. These data can then be reduced to point or bar graphs or to isopleth maps. Each of the models have "stand alone" capabilities provided all the inputs are available. The salinity model, however, is the more restricted in this sense in that it requires the advective inputs at every computational cell. This input is not usually available from data-collection programs and must almost always be generated through tidal computations.