The Landscape Hydrologic Capacitance Hypothesis: Exploring hydrogeomorphic and hydroclimatic drivers of wetlandscape hydrology

Wetlands provide important physical, chemical, and biological functions to downstream waters. In many low-gradient, poorly-drained landscapes, wetland water storage and connectivity drive these functions from local to landscape scales; and importantly, these hydrologic characteristics are altered by drainage, groundwater withdrawals, and climate change. Here, we use a combination of empirical measurements and novel topographic analyses to explore hydroclimatic and hydrogeomorphic drivers of wetland water storage and connectivity across the Delmarva Peninsula [Eastern Shore of Maryland, USA]. Empirical measurements include one year of continuous wetland water level in 18 depressional wetlands, upland groundwater levels adjacent to six wetlands, and surface water levels at the outlet of six headwater catchments. Our topographic analyses use a raster-based approach to quantify wetland-scale water storage capacity, catchment-scale water storage capacity, and the vertical distribution of that storage at the catchment-scale. Initial results highlight the seasonality of wetland storage and connectivity, an inverse relationship between catchment-scale storage capacity and wetland water level recession rates, and the impact of the relative elevation of surface water storage on surface water-groundwater exchange. Taken together, our results support the Landscape Hydrologic Capacitance hypothesis - where our empirical observations suggest that wetlands are both a subsidy to the surrounding surficial aquifer during seasonal drawdown and a buffer to runoff during episodic storm events. Further, our results highlight the opportunity to use wetland restoration and conservation as a potential tool for managing groundwater supplies, water quality, and carbon emissions from local to landscape scales.