Wetland Monitoring, Characterization and Modelling under Changing Climate in the Canadian Subarctic

Abstract

Subarctic wetlands that exist as bogs, fens, swamps, marshes and shallow water, comprise 3% of the Canadian landscape. They have been recognized as important ecotones between the arctic tundra and boreal forest. Recently, there has been growing research interest in the hydrological characteristics of arctic and subarctic wetland systems in the need for more efficiently conserving wetlands and assessing climate change related impacts. This research targets the Deer River watershed near Churchill, Manitoba, which represents a typical subarctic wetland system in the Hudson Bay Lowlands. An extensive field investigation was first conducted during the summer from 2006 to 2008 to facilitate in-depth understanding of the wetland hydrology. The results provided evidence to indicate a strong relationship between air temperature and evapotranspiration. Permafrost table, soil moisture and streamflow were monitored and analyzed to advance the acknowledgement of the climatic, geographical and hydrological characteristics of subarctic wetlands. To quantify the water cycle and further validate the findings from field investigation, a Canadian distributed hydrological model, WATFLOOD, was employed to simulate the hydrologic processes in the targeted watershed. The results demonstrated that snowmelt in the spring season (April-June) was the major source of water supplement of subarctic wetlands. Most light and moderate rainfall events in summer (July-September) generated relatively small amounts of runoff which can be related to canopy interception, depression storage, porous soil layers, impermeable permafrost and intensive evapotranspiration. A lag of 2-8 days between the peaks of rainfall and stream runoff was observed in both summer and fall. This study is expected to benefit wetland conservation and the assessment of climate change related impacts in the Canadian northern regions.

Keywords: subarctic wetland, field investigation, hydrological modeling, permafrost, snowmelt