Field Investigation and Hydrological Modelling of a Subarctic Wetland - the Deer River Watershed

Recently, investigation and conservation of subarctic wetlands has been recognized as an attractive route. To gain insight of the interactions between hydrology and atmosphere of the second largest wetland in Canada - the Hudson Bay Lowlands (HBL), the semi-distributed land use-based runoff process (SLURP) hydrological model was applied to a typical subarctic wetland - the Deer River watershed over a 20-year period (1978-1997). Sensitivity analysis, calibration and validation of the model identified a number of distinguishable hydrological features of subarctic wetlands as well as model deficiencies. Snowmelt was the major source of water recharge in subarctic wetlands and constituted approximately half of the average annual runoff in the Deer River watershed. The peaks of the simulated spring runoff were 34% lower than the observed ones in average which could be attributed to the effects of shallow permafrost that impeded the infiltration of melt water. Runoff of rainfall water during the summer season occurred only during storms due to canopy interception, depression storage, soil porosity, impermeable permafrost, and intensive evapotranspiration. A lag of 2-8 days between the peaks of streamflow and rainfall was observed through both field investigation and modeling results. The numerous seasonally connected ponds/lakes stretching over the middle and lower reach of the watershed behaved as buffers and significantly prolonged the concentration time in summer and fall. The findings will help build a scientific basis for advancing the knowledge of the hydrologic cycle and impacts of climatic changes on sub-arctic wetlands.