The Peculiar Hydrology of West-Central Florida’s Sandhill Wetlands, Ponds, and Lakes –Part 2: Hydrogeologic Controls

Abstract

This study investigates hydrogeologic controls on a peculiar, poorly studied type of geographically isolated wetland in west-central Florida, USA, locally referred to as “sandhill” (or “xeric”) wetlands. Their peculiarity lies in their connectivity to a large regional aquifer, which controls their hydrology. Evidence for this connectivity was presented in Part I of this two-part series, but the mechanisms of their connectivity and ecohydrologic expression were yet undocumented. To make these determinations, we used geophysical, lithologic, hydrologic, and ecological data to construct hydrogeologic configurations for five distinct sandhill wetland types. From these configurations, two conceptual models were derived. The first model depicts the mechanisms by which sandhill wetlands connect to the regional aquifer. Three types of connectivity are proposed, each a function of the degree and depth of aquifer confinement: 1) direct-due to wetland embedment directly in the unconfined regional aquifer; 2) indirect-due to embedment in a surficial aquifer, where groundwater exchange with the regional aquifer occurs through breaches in the semi-confining unit; and 3) none-due to embedment in a surficial aquifer where groundwater exchange with the regional aquifer does not occur because the semi-confining unit is too deep. The second model conceptualizes sandhill wetland ecohydrologic expression as a function of depression geomorphology and the range of the regional water table. These models provide the basis of understanding of sandhill wetland, pond, and lake ecohydrology and can improve how natural resource managers classify, assess, and preserve these unique features, regionally and wherever wetlands of similar hydrogeologic control are found.