Spring and Summer Runoff Hydrology of a Subarctic Patterned Wetland

Abstract

Patterned wetlands occur extensively throughout the Canadian subarctic and boreal regions. These areas are important because of their hydrological and chemical interaction with other ecosystems, aquatic and terrestrial. However, there is a lack of knowledge on the hydrology of many wetland types in the boreal and subarctic regions, particularly patterned fens. This paper examines the relationship between the flux and storage of water both within a patterned wetland and between it and the adjacent ecosystems. It is hypothesized that patterned wetlands alternate between two hydrological phases. The first occurs when the water supply exceeds the depression storage capacity of the patterned wetland pools, and the wetland drains as a single source area, while receiving inputs from adjacent nonwetland portions of the basin. As a result, basin discharge during such periods is relatively high. The second phase occurs when the loss of water through seepage and evaporation leads to disconnection of the wetland pools into separate microcatchments within the pool-ridge complex. Under this condition, basin discharge is relatively low, maintained only by a limited source area immediately upstream of the outlet. Through an explanation of the hydrological processes and linkages among subsystems, an understanding of the processes governing runoff from a basin with a patterned wetland at its outlet is obtained. It is demonstrated that the discharge response of patterned wetlands is distinctive from that of other wetland types because the large storage capacity of the wetland pools delays runoff contributions from large portions of the wetland and surrounding basin.