Wetland Connectivity Thresholds and Flow Dynamics From Stage Measurements

Depressional wetlands are dominant features in many low-gradient landscapes, where they provide water storage and exchange. Typical basin morphology enables water storage during drier periods, when surface flow paths are disconnected and exchange is limited to slower groundwater flow paths. Under wetter conditions, wetland stage can exceed surface connection thresholds, activating surface flow paths to downstream waters. Empirical methods are needed to quantify these dynamics and thus to assess their role in landscape hydrology and associated functions. We developed a new water budget-based approach to enumerate connectivity thresholds and flows from stage measurements. We propose that this approach, termed Connectivity and Flow from Stage (CFS), has broad applicability across wetlandscapes. We applied the CFS method in the Big Cypress National Preserve, where we hypothesized that surface connectivity episodes control water and solute flux, with consequences for exported carbonate weathering products and thus for karst landform evolution. Across five study wetlands, this analysis detected surface connectivity thresholds and assessed temporal flow dynamics. Imputed connectivity thresholds were clear from stage-dependent net flow dynamics and aligned well with LiDAR-derived thresholds. Water export occurred overwhelmingly when stage exceeded these thresholds, indicating that water and solute export from these wetlands is dominated by periods of enhanced landscape connectivity. Notably, the presented CFS method can quantify wetland connectivity thresholds from stage data, even without supporting geomorphic information. This approach is useful for understanding hydrologic controls on biogeomorphic evolution in this particular karst landscape, and more broadly for inferring wetland connectivity patterns and magnitudes in other wetlandscape settings.

Duke Scholars

Author James Brendan Heffernan Environmental Natural Science