Current and future projections of glacier contribution to streamflow in the upper Athabasca River Basin

Abstract The Athabasca River Basin in Alberta, Canada, is of international significance, and understanding water supply is critically important to the sustainability of the region. In the upper Athabasca River Basin, glaciers covered 272 km2 (2.8% of the watershed) as of 2010, but less than 50 km2 are projected to remain by the end of the twenty-first century. This study investigated glacier contributions to streamflow for a baseline (1981–2010) period and two climate change scenarios (RCP 4.5 and RCP 8.5, 2011–2100) using a hydrological model that explicitly accounts for glacier retreat. Simulated discharge from glaciers (i.e. including all glacier ice, firn and snow melt) contributed 4%–6% of annual streamflow and 20%–30% in August during the baseline period. The model projects an increase in glacier discharge in the coming decades with a later decline by the middle of the twenty-first century. Although glacier discharge is projected to increase in the short term, this water source is non-renewable barring a stabilization of air temperatures in the region, something not currently projected by any climate model. While streamflow in the upper Athabasca River Basin was projected to increase on an annual time scale, streamflow during the late-summer months was projected to decrease by up to 58% by 2100. These simulations follow findings from across western Canada and globally, highlighting that ‘peak water’ is not solely driven by changes in glacier discharge and is also responsive to changes in climate. Late summer is a period when water demands are the highest, water shortages already occur, water quality is the most sensitive and the ability to navigate throughout watercourses in the basin is limited. These findings emphasize the importance of changes in streamflow timing and seasonality and present major challenges for water management in the Athabasca River Basin and elsewhere in glacierized catchments over the coming decades.