Water Balance of Lakes in the Continental Arctic: An Arid Zone Case Study

Abstract:

Stable isotope mass balance using oxygen-18 and deuterium has been applied to study spatial evaporation and water balance trends across continental northern Canada, a remote region of greater than 275,000 km² characterized by significant seasonal aridity and strong gradients in hydroclimate and vegetation. Calculated catchment-weighted evaporation losses based on a lake survey in the 1990s were estimated at ~10–15% in tundra areas draining into the Arctic Ocean to as high as 60% in forested subarctic areas draining to the Mackenzie River via Great Bear or Great Slave Lakes. Open-water evaporation was found to generally decrease with increasing latitude, accounting for 5 to 50% of total evapotranspiration. Two long-term studies initiated in the 1990s, and carried on for 20+ years, confirm many of the findings of the initial survey and now provide a complimentary perspective of temporal variations in water balance along two representative string-of-lakes drainages located in boreal and tundra settings. For a tundra watershed, the study reveals important lake-order-dependent patterns of evaporation/inflow, evaporation/evapotranspiration, land-surface-runoff/precipitation and discharge/precipitation. For a boreal watershed, the analysis also reveals that fluctuations in effective drainage area due to intermittent connectivity between lakes during dry periods can be an important driver of downstream isotopic signals.