THE EFFECT OF GLACIER WASTAGE ON THE FLOW OF THE BOW RIVER AT BANFF, ALBERTA, 1951-1993

A surface area/volume relationship was used to estimate total glacier volumes for the highly glacierized Hector Lake Basin (281 km(2)) in th e Canadian Rockies in the years 1951 and 1993. The change in volume wa s calculated and this value then extrapolated up to the Bow Basin at B anff (2230 km(2)) based on relative proportions of glacier cover. The mean net glacier volume loss estimate of 934 x 10(6) m(3) was divided into annual proportions of glacier wastage and storage using a local m ass balance record collected at Peyto Glacier in the Mistaya Valley, c ontiguous to the Bow Basin. Unfortunately, the record began in 1966 an d a hind-cast to 1952 (hydrological year) was necessary. Banff maximum summer temperature and Lake Louise snow course data were used as surr ogates for summer and winter glacier mass balance, respectively. Month ly wastage proportions were estimated for 1967-1974 by using modelled values of glacial melt as a template. Glacier wastage inputs to and st orage held back from the Bow River hydrograph at Banff were compared w ith known basin yields to assess the hydrological effects of glacier v olume change. For 1952-1993, the average annual wastage/basin yield ra tio was found to be around 1.8%. For the extremely low flow year of 19 70 this ratio increased to 13%. The proportion of flow derived from gl acier wastage in August of this year was estimated to be around 56%. A lthough the results tend to confirm the regulatory effect of glaciers on stream flow, it was found that in some years of low flow this situa tion has been aggravated by water being held in glacial storage. (C) 1 998 John Wiley & Sons, Ltd.