The effect of glacier wastage on the flow of the Bow River at Banff, Alberta, 1951–1993

Abstract

A surface area/volume relationship was used to estimate total glacier volumes for the highly glacierized Hector Lake Basin (281 km2) in the Canadian Rockies in the years 1951 and 1993. The change in volume was calculated and this value then extrapolated up to the Bow Basin at Banff (2230 km2) based on relative proportions of glacier cover. The mean net glacier volume loss estimate of 934×106 m3 was divided into annual proportions of glacier wastage and storage using a local mass balance record collected at Peyto Glacier in the Mistaya Valley, contiguous to the Bow Basin. Unfortunately, the record began in 1966 and a hind-cast to 1952 (hydrological year) was necessary. Banff maximum summer temperature and Lake Louise snow course data were used as surrogates for summer and winter glacier mass balance, respectively. Monthly wastage proportions were estimated for 1967–1974 by using modelled values of glacial melt as a template. Glacier wastage inputs to and storage held back from the Bow River hydrograph at Banff were compared with known basin yields to assess the hydrological effects of glacier volume change. For 1952–1993, the average annual wastage/basin yield ratio was found to be around 1·8%. For the extremely low flow year of 1970 this ratio increased to 13%. The proportion of flow derived from glacier wastage in August of this year was estimated to be around 56%. Although the results tend to confirm the regulatory effect of glaciers on stream flow, it was found that in some years of low flow this situation has been aggravated by water being held in glacial storage. © 1998 John Wiley & Sons, Ltd.