Effects of Beaver Dams on Subarctic Wetland Hydrology

Abstract

Beaver dams are ubiquitous in subarctic wetlands, where runoff in the flat terrain is highly prone to changes as the stream courses are modified by beaver activities. Depending on the state of preservation, stream flow can overtop or funnel through gaps in the dams, leak from the bottom of the dams or seep through the entire structure. Peak and low flows are regulated by these dams to a varying extent. The formation of beaver ponds causes local flooding, while the open water surfaces of the ponds increase water loss from the wetlands. Water spilled from the dams may cause diversion channels to produce complex drainage patterns. Comparing the water balance of basins with and without a beaver dam at its outlet confirms that the dammed basin lost more water to evaporation, suppressed the outflow and increased the basin water storage.