Long-Term Patterns of Geographically Isolated Wetland Inundation and Hydroperiods from the Gulf Coastal Plain

Wetland structure and function are largely emergent properties of hydrology and the variability of inundated conditions. In the U.S., hydrology is also central to defining legal status of wetlands at the federal level within a continuum of regulatory and conservation programs, with much recent focus on isolated wetlands. Here, we use long-term (1994–2023) water level data from 32 geographically isolated wetlands across Ichauway, a private research facility in the karst Dougherty Plain of southwestern Georgia, to identify spatial and temporal patterns of hydroperiod and identify drivers of inundation over the 30-year record. Wetlands at Ichauway are identified by their vegetation type as marshes, cypress-gum swamps, and cypress savannas. Wetland inundation showed distinct seasonal patterns, with typical inundation between December and early summer. Longer-term, inundation patterns were linked to regional water availability and drought conditions. Hydroperiods in swamps were longer than in marshes and cypress savannahs, and recession rates were faster in cypress savannahs and marshes compared to swamps. Across all wetlands, hydroperiods were strongly linked to variability in the regional water budget, with patterns of groundwater and stream water elevation, strongly influencing the hydrology of isolated wetlands. Our analysis leverages long-term data spanning multi-year climate cycles to inform patterns of inundation in isolated wetlands at the landscape scale.