Wetlands have a very interesting interface between hydrology and terrestrial ecosystems. Wetland communities evolve because of specific hydrologic conditions (i.e. poor drainage, excess precipitation). Yet, as a wetland develops, the vegetation communities affect the original hydrologic setting. Eventually, the hydrologic system and the ecosystem develop a coexisting-dependent relationship. The Glacial Lake Agassiz Peatlands and the Everglades/Big Cypress developed in similar hydrologic settings. Both occur in expansive areas of low relief with excess precipitation (except Big Cypress) and receive groundwater discharge. However, due to differences in climate these wetland systems host very different vegetation communities. Raised bogs, fens, spring fens and tree islands dominate the Glacial Lake Agassiz Peatlands. The Everglades/Big Cypress are dominated by opens sloughs, wet prairies, cypress domes and tree islands. Despite their similar origins, these wetland systems have developed very different hydrologic systems. The flow of water in the Glacial Lake Agassiz Peatlands is topographically driven through the peat. There are fewer fluctuations in water table elevation. In the Everglades/Big Cypress there is much more open water. Water flow is often topographically driven, however, there is considerable influence by the wind on the movement of water. Furthermore, there is a very distinct hydroperiod with seasonal variations in water depth. How these differences in hydrology developed and their impact on the wetlands will be presented.