Stable isotopic and geochemical variability within shallow groundwater beneath a hardwood hammock and surface water in an adjoining slough (Everglades National Park, Florida, USA)

A decade-long monitoring study in the Everglades reveals that shallow groundwater beneath hardwood hammocks remains geochemically stable year-round, contrasting with surface waters that fluctuate due to rainfall dilution and external inputs. Stable isotopic analysis (δ¹⁸O, δD) shows surface water enrichment and evaporation signatures, while shallow groundwater maintains consistent values near -2.4‰ for δ¹⁸O and -12‰ for δD. The study identifies two distinct moisture sources for precipitation—maritime in fall/winter and continental-influenced in spring/summer—with tropical cyclones or fronts as primary recharge mechanisms. Ion chemistry further confirms external canal inputs from drained agricultural areas, highlighting the complex hydrological dynamics of this UNESCO-listed ecosystem.

Florea, L. J., & McGee, D. K. (2010). Stable isotopic and geochemical variability within shallow groundwater beneath a hardwood hammock and surface water in an adjoining slough (Everglades National Park, Florida, USA). Isotopes in Environmental and Health Studies, 46(2), 190–209. https://doi.org/10.1080/10256016.2010.494770