The Peculiar Hydrology of West-Central Florida’s Sandhill Wetlands, Ponds, and Lakes—Part 1: Physical and Chemical Evidence of Connectivity to a Regional Water-Supply Aquifer

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The sandhill wetlands, ponds, and lakes of west-central Florida, USA, are an understudied, poorly understood variant of geographically isolated features. Their karst origin and xeric setting impart a characteristic ecohydrology, which has been attributed to their apparent connectivity to a regional water-supply aquifer. This study uses physical and geochemical hydrologic data to provide evidence of this connectivity. The findings presented here debut these rare features, which advances their fundamental understanding at a time when increasing anthropogenic pressures risk further loss and degradation. From these findings, the hydrologic nature of sandhill wetlands, ponds and lakes is characterized, which may be useful in distinguishing them from others with different hydrologic controls and for identifying features of similar connectivity, karst or otherwise, wherever they may be found. Water levels and/or geochemistry were compared for 12 wetlands, five ponds, two lakes, and 12 monitor wells (10 constructed in limestone, two in surficial sand) in west-central Florida. Hydrograph and regression analyses indicate similar widely ranging water levels (2–5 m) for sandhill features and wells that are both analogous in elevation and highly correlated with each other (0.84 ≤ R2 ≤ 0.99). Sandhill feature geochemistry also reflects that of the monitor wells, varying relative to the depth of the rainwater-limestone water mixing zone. Findings here suggest sandhill wetland/water features are surface water expressions of the underlying unconfined regional aquifer hydrology, distinguishing them from isolated features elsewhere and establishing them as a groundwater endmember along the hydrologic continuum.