Abstract
This study focused on the effects of glacier wastage on streamflow in the Canadian portion of the Columbia River headwaters over the period 1977 to 2017. Between 1985 and 2013, glacier coverage decreased by up to 2% of catchment area for the 35 study catchments. The mean wastage flux contribution to streamflow had a positive relation with fractional glacier coverage and an inverse relation with catchment water yield. Glacier mass change estimates suggest that wastage flux contributions declined between 1985-1999 and 2000-2018, but the estimates are subject to substantial uncertainty. Annual wastage flux contributions over a four-year period for two study catchments ranged from 8 to 13% of annual water yield for a catchment with 17% glacier cover, with glaciers extending below treeline, and 9 to 19% for a smaller alpine catchment with 57% glacier cover. After accounting statistically for climatic forcing and non-glacial contributions to streamflow, August runoff from glacierized catchments decreased through time at a rate that was linearly related to loss of glacier cover. The analyses suggest that glacier-melt contributions to August runoff have already have passed peak water, and that these reductions have exacerbated a regional climate-driven trend to decreased August streamflow contributions from unglacierized areas.
Highlights
Glaciers make significant contributions to streamflow and water resources in many parts of the world (Barnett et al, 2005; Kaser et al, 2010)
Between 1985 and 1999, mass changes derived from the digital elevation models indicate a mean rate of glacier storage loss that varied among catchments from about 0.1–0.9 m w.e. a−1, with a mean of 0.55 ± 0.13 m w.e. a−1
The glacier wastage flux contribution to annual water yield had a positive relation with fractional glacier coverage and an inverse relation with catchment water yield
Summary
Glaciers make significant contributions to streamflow and water resources in many parts of the world (Barnett et al, 2005; Kaser et al, 2010). Contributions of glaciers to streamflow are important during periods of warm, dry weather, and have been detected even for glacier cover as low as about 1 or 2% (Stahl and Moore, 2006; Huss, 2011). It is generally accepted that glacier contributions to streamflow in the presence of climatic warming should follow a trajectory that begins with an initially increasing phase associated with rising snowlines and loss of firn, with streamflow eventually peaking and declining as glaciers retreat either until they disappear or reach a new glacio-climatic equilibrium (Jansson et al, 2003; Moore et al, 2009; Baraer et al, 2012). Based on a review of 15 studies from around the world, Casassa et al (2009) observed that increasing trends tended to be found in high-elevation
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