The influence of restoration on the hydrology of a karst wetland, Everglades (FL, USA)

Predicting and evaluating the influence of human modifications on karst wetland hydrology is challenging, as the groundwater and surface water have a close hydraulic connection. An ideal place to study the influence of restoration on the hydrologic interactions in karst wetlands is the Everglades (FL, USA). Predominantly underlain by a karst limestone aquifer, the Everglades has been hydrologically altered over the last century to provide flood protected agricultural and urban lands. These human modifications have resulted in wetland loss, reduced surface water flow and altered water levels. Recent restoration efforts along the eastern boundary of Everglades National Park, an area known as the Rocky Glades, have moved away from direct discharge of canal water in favor of a diffuse method to rehydrate the Rocky Glades and support downstream freshwater delivery to downstream slough. Four retention basins and associated pump stations were constructed and put into operation between 2000-2002 to create a hydrologic divide between the Park and the adjacent canal system.

To determine the influence of these new restoration efforts, as well as climate on the hydrology of the Rocky Glades, water inputs and outputs to the watershed were compared using a water budget, while the Mann-Kendall test was used to detect temporal trends in groundwater and surface water levels from 1997-2011. Results indicate the reduction in surface water flow out of the Rocky Glades was concurrent with a significant decline in rainfall inputs to the watershed over the last 15 years. After 2002, surface water inputs into the retention basins were able to explain over half the variability observed in the surface water discharge out of the Rocky Glades. The annual variation in the change of storage also increased across the Rocky Glades following 2002. Over this period a significant decline was detected in the average dry season (March-May) surface water levels at 41% of the stages, while average wet season (August-September) surface water levels remained fairly constant. These findings suggest that restoration efforts may have been effective at maintaining wet season surface water levels in the Rocky Glades given the reduced rainfall input, but also resulted in more variable hydrologic conditions.