2nd UF Water Institute Symposium Abstract

Submitter's Name David Kaplan
Session Name Poster Session: Hydrologic, Biogeochemical and Ecological Processes 2
Category Hydrologic, biogeochemical and ecological processes
Poster Number 222
Author(s) David Kaplan,  UF Agricultural and Biological Engineering
  Rafael Muñoz-Carpena,  UF Agricultural and Biological Engineering
  Yongshan Wan, South Florida Water Management District
  Marion Hedgepeth, South Florida Water Management District
  Dick Roberts, Florida Park Service (Retired)
  Linking River, Floodplain, and Vadose Zone Hydrology to Improve Restoration of a Coastal River Impacted by Saltwater Intrusion
  Floodplain forests provide unique ecological structure and function, which are often degraded or lost when watershed hydrology is modified. Restoration of impacted ecosystems requires an understanding of surface water, groundwater, and vadose (unsaturated) zone hydrology in the floodplain. Soil moisture and porewater salinity are of particular importance for seed germination and seedling survival in systems impacted by saltwater intrusion, but are difficult to monitor and often overlooked. This study contributes to the understanding of floodplain hydrology in one of the last bald cypress (Taxodium distichum [L.] Rich.) floodplain swamps in southeast Florida (USA) by investigating soil moisture and porewater salinity dynamics in the floodplain of the Loxahatchee River, where reduced freshwater flow has led to saltwater intrusion and a transition to salt-tolerant, mangrove-dominated communities. Twenty-four dielectric probes measuring soil moisture and porewater salinity every 30 minutes were installed along two transects perpendicular to the river—one in an upstream, freshwater location; the other in a downstream tidal area. Data collected over four years quantified the spatial variability and temporal dynamics of vadose zone hydrology and showed that soil moisture can be closely predicted based on river stage and topographic elevation (coefficient of efficiency = 0.83). Porewater salinity rarely exceeded tolerance thresholds for bald cypress upstream, but did so in some downstream areas, explaining observed vegetation changes. The results offer a methodological and analytical framework for floodplain monitoring in other locations where restoration success depends on vadose zone hydrology and provide relationships for evaluating proposed management scenarios for the Loxahatchee River. (Additional authors: Fawen Zheng, SFWMD and Rob Rossmanith, FPS)