Characterization of a Sub-arctic Wetland System Through Field Investigation and Hydrological Modelling

The considerable impact of wetlands on water storage and distribution, carbon cycle, climate change and ecosystems in sub-arctic regions has been widely noticed. To understand and clarify the hydrological characteristics of wetland systems is inevitable and crucial for the purposes of modeling the water cycle and predicting how the water cycle may vary in the next century. To gain insight of the interaction between hydrology and atmosphere of sub-arctic wetlands in the Hudson Bay Lowlands, extensive field investigations were conducted during 2006 and 2008 in the Deer River watershed near Churchill, Manitoba, Canada. The 28-year historic data (1978-2005) and the 3-year field observation provided evidence to indicate a warming climate in the watershed. Frost table, soil moisture and streamflow were also monitored to advance the acknowledgement of the climatic, geographical and hydrological characteristics of the subarctic wetlands. Two distributed hydrological models, SLURP and WATFLOOD, were employed to simulate the hydrologic cycle and reveal the distinguishable features of sub-arctic wetlands. It was observed that the snowmelt in the spring season produced the highest peak discharges and contributed to the majority of the annual streamflow. The peaks of the simulated spring flows were to some extent lower than the observed ones. This could be attributed to the effects of extensive wetland ponds and shallow permafrost tables which could restrict the infiltration of rainwater and drive the snowmelt to form spring flow peaks. It was also shown that most of the small or moderate rainfall events during the summertime were unable to generate noticeable surface runoff possibly due to canopy interception, depression storage, porous soil layers, descending permafrost table and intensive evapotranspiration. The findings helped build a scientific basis for supporting in-depth understanding of the hydrologic cycle and impacts of climate change on sub-arctic wetlands.