Hydrological Dynamics and Connectivity of Wildfire Impacted Rock Barrens Ephemeral Wetlands

Abstract:

Peat-filled ephemeral wetlands, which form within bedrock depressions, provide important ecohydrological functions on Ontario’s rock barrens landscape through the storage of water and the regulation of hydrological connectivity of sub-catchments and hydrological response units (HRUs). The fill-and-spill processes which govern the discharge of water from these ephemeral wetland systems provide critical water storage and regulate the rainfall-runoff response at the watershed scale. Wildfire removes vegetation as well as peat through smouldering combustion which may lead to changes in the hydrological dynamics and connectivity of these wetlands with cascading downstream effects. Given that wildfire frequency and area burned are increasing there is an urgent need to assess the connectivity, storage capacity and hydrological dynamics of wildfire-impacted ephemeral wetlands on the rock barrens landscape. We hypothesized that peat loss from wildfire-impacted ephemeral wetlands would increase the storage capacity and wetland-wide specific yield and increase thresholds to discharge. We also hypothesized that the increase in storage capacity would reduce downstream hydrological connectivity. To examine this, we compared water storage and runoff response of three burned and unburned rock barrens ephemeral wetlands one and two years following the Parry Sound 33 wildfire. We also parameterized a hydrological model to provide further insights into the impacts of wildfire, by examining landscape and wetland morphology, on the hydrological behaviour of ephemeral wetlands. The increase in discharge thresholds from ephemeral wetlands may offset the commonly observed increase in runoff from upland slopes following wildfire.