A regional scale hydrogeologic model has been developed to estimate the magnitude of submarine groundwater discharge to the coastal waters of southeastern Louisiana. The model domain incorporates both the onshore recharge area of terrestrially derived freshwater, and fluid circulation within the sediments on the continental shelf. The hydrogeologic properties of these sediments, which form part of the Coastal Lowlands Aquifer System, have been well-characterized in earlier studies. The low topographic relief of the coastal plain and an extensive zone of seawater intrusion are key features of the groundwater flow system. Model calculations suggest that no water containing a substantial component of terrestrial origin discharges on the continental shelf. Rather the near-shore coastal zone serves as a groundwater recharge area of saline water that then forms the seawater recirculation system beneath the coastal plain. The modeling results are consistent with interpretations of the rates of submarine groundwater discharge derived from geochemical tracers, presented in a companion paper by McCoy et al. (2007).