The Influence of Glacial Cover on the Variability of Annual Runoff, Coast Mountains, British Columbia, Canada

The coefficient of variation of annual runoff (Cv) tends to decrease as fractional glacial cover (f) increases from 0.0 to 0.27 for watersheds draining the Coast Mountains of British Columbia, Canada. The best-fit relationship for this range of glacial cover, Cv = 0.173 – 0.347 f, explains 62% of the variance of Cv and has a standard error of estimate of 0.022. The only point outside this range has f = 0.63, and has the second highest Cv of all points. This datum is consistent with the finding from previous studies that Cv attains a minimum at intermediate values of f. The sensitivity of Cv to changes in f (dCv/df), calculated using pairs of nearest watersheds to help isolate glacial influences from sub-regional climatic variations, has a mean of −0.313. Application of empirical Cv-f relationships may be hampered by uncertainties in Cv and f.