Limitations were periodically encountered using the explicit, time-lagged approach to couple the surface-water and ground-water models. For some sensitivity simulations with very large leakage rates, convergence could not be achieved during solution of the ground-water flow equation. Evaluation of the convergence problems indicated that very large leakage rates caused numerical oscillations in the implicit solution. Ground-water heads measured in the field can respond quickly to hydrologic stresses. For the Everglades application of the integrated model, however, large leakage rates may persist throughout the day in the model, because of the 1-day length of the stress period in SEAWAT, whereas actual leakage rates would decrease as ground-water heads respond more quickly. A decrease in the length of the ground-water stress period could probably have improved convergence. These convergence problems were encountered only in a few instances, and thus the day lag, which is computationally many times faster than using an hourly lag or fully implicit solution, was a necessity for this particular application. Future efforts using the integrated model should follow the example of Fairbanks et al. (2001) and focus on determining the relation between accuracy and efficiency for different coupling approaches and timestep lengths.

The Buttonwood Embankment clearly is an important physiographic feature in the Taylor Slough area. Model results and field observations suggest that freshwater flow into Florida Bay occurs primarily through the coastal creeks, rather than as overtopping of the embankment. This flow pattern has allowed field investigations to quantify with a high level of certainty the flow exchanges between the coastal wetlands and Florida Bay (Hittle, 2000; Hittle et al., 2001). Confidence in the predictive capability of the integrated model is due largely to the accuracy and long-term record length of creek discharge data. Many coastal wetlands in other locations, however, are not separated from the adjacent marine water body by an embankment or barrier to overland flow, and thus measurement of freshwater outflows is not as straightforward.