The role of recharge and evapotranspiration as hydraulic drivers of ion concentrations in shallow groundwater on Everglades tree islands, Florida (USA)

Abstract

Recently, evapotranspiration has been hypothesized to promote the secondary formation of calcium carbonate year‐round on tree islands in the Everglades by influencing groundwater ions concentrations. However, the role of recharge and evapotranspiration as drivers of shallow groundwater ion accumulation has not been investigated. The goal of this study is to develop a hydrologic model that predicts the chloride concentrations of shallow tree island groundwater and to determine the influence of overlying biomass and underlying geologic material on these concentrations. Groundwater and surface water levels and chloride concentrations were monitored on eight constructed tree islands at the Loxahatchee Impoundment Landscape Assessment (LILA) from 2007 to 2010. The tree islands at LILA were constructed predominately of peat, or of peat and limestone, and were planted with saplings of native tree species in 2006 and 2007. The model predicted low shallow groundwater chloride concentrations when inputs of regional groundwater and evapotranspiration‐to‐recharge rates were elevated, while low evapotranspiration‐to‐recharge rates resulted in a substantial increase of the chloride concentrations of the shallow groundwater. Modeling results indicated that evapotranspiration typically exceeded recharge on the older tree islands and those with a limestone lithology, which resulted in greater inputs of regional groundwater. A sensitivity analysis indicated the shallow groundwater chloride concentrations were most sensitive to alterations in specific yield during the wet season and hydraulic conductivity in the dry season. In conclusion, the inputs of rainfall, underlying hydrologic properties of tree islands sediments and forest structure may explain the variation in ion concentration seen across Everglades tree islands. Copyright © 2012 John Wiley & Sons, Ltd.

Gaseous Carbon Emissions (Methane and Carbon Dioxide) from Wetland Soils in a Re-created Everglades Landscape

“…Second, this method would allow for differentiation in the analysis between the effects of inundation at various depths within the soil matrix. Finally, it was hoped that sampling pore-water might be slightly less susceptible to the changing availability of water, since tree islands (such as those in LILA) have been found to hydraulically pull groundwater toward their roots, thereby sustaining water levels at higher elevations within tree islands than the surrounding water table Sullivan et al, 2012). Permanentlyinstalled pore-water sippers therefore allowed for more consistent sampling across sites over seasonal changes in water levels.…”

Numerical Modeling of the Effects of Hydrologic Conditions and Sediment Transport on Geomorphic Patterns in Wetlands

“…3.2). This assemblage is a replica of ridge and slough and tree island landscape feature of the greater Everglades Sullivan et al, 2010;Sullivan et al, 2012).…”

Water-Rock Interactions and Seasonal Hydrologic Processes in Constructed Everglades Tree Islands

“…They are maintained according to an established hydrograph with the highest levels typically occurring from September to January, flooding the tree islands, and the lowest levels occurring from April to June (Sullivan et al, 2011(Sullivan et al, , 2014a(Sullivan et al, , 2016. The water within LILA is managed by a large electric pump (1.84 m 3 /s), a series of water control structures, and recording stage gauges, allowing researchers to manage water levels and flow rates within each macrocosm (Aich et al, 2011).…”

“…Groundwater with elevated IS and supersaturated with respect to CaCO3 suggest a potential for calcite precipitation within the soils of tree islands in the Everglades, which in turn, could contribute to soil accretion rates on time scales of centuries to millennia (Sullivan et al, , 2014a(Sullivan et al, , 2014b(Sullivan et al, , 2016.…”