A coupled flow-temperature model has been developed and verified for a 27.9-km reach of the Chattahoochee River between Buford Dam and Norcross, Ga. Flow in this reach of the Chattahoochee is con tinuous but highly regulated by Buford Dam, a flood-control and hydroelectric facility located near Buford, Ga. Calibration and verification utilized two sets of data collected under highly unsteady discharge conditions. Existing solution techniques, with certain minor improvements, were applied to verify the existing technology of flow and transport modeling. The linear, implicit finite-difference flow model was calibrated by use of a depth profile obtained at steady low flow and unsteady flow data obtained in March 1976. During the calibration period, the model was generally able to reproduce observed stages to within 0.15 m and discharges at less than 100 m3/s, to within 5 percent. Peak discharges of about 200 m3/s were underestimated by about 20 percent. During the verification period, October 1975, the flow model reproduced observed stage changes to within about 0.15 m, and its timing and overall performance was considered to be very good. Dye was added to the upstream end of the river reach at a constant rate while the river flow was highly unsteady. The numerical solution of either the conservative or nonconservative form of the masstransport equation did an excellent job of simulating the observed concentrations of dye in the river. The temperature model was capable of predicting temperature changes through this reach of as large as 5.8°C with a RMS (rootmean-square) error of 0.32°C in October 1975 and 0.20°C in March 1976. Hydropulsation has a significant effect on the water temperature below Buford Dam. These effects are very complicated because they are quite dependent on the timing of the release with respect to both the time of day and past releases.

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A single-input linear system model and a multiple-input linear system model are compared to a finite difference model. Comparisons are based on the ability of the models to predict discharge at the downstream end of a 24.14-km reach of prismatic channel. Four types of channels and two slopes covering a wide range of conditions are evaluated. The single-input model compares favorably in cases where flood wave celerity does not vary greatly with discharge. The multiple-input model can be made to compare favorably in all cases. Linear model parameters cannot be set accurately without calibration, except in the case of rectangular channels. The single-input model is approximately one sixth as costly as the finite difference model, and the multiple-input model is approximately one half as costly for the conditions investigated.