John Wiley & Sons Ltd.
British Columbia, cryosphere, double mass curve, glacier melt, glacier runoff, hydrograph seperation
Alpine glaciers and perennial snow fields are important hydrologic elements in many mountain environments providing runoff during the late summer and during periods of drought. Because relatively long records of glacier mass–balance data are absent from many glacierized catchments, it remains unclear to what extent shrinking perennial snow and glaciers have affected runoff trends from these watersheds. Here, we employ a hydrograph separation technique that uses a double mass curve in an attempt to isolate changes in runoff due to glacier retreat and disappearance of perennial snow. The method is tested using hydrometric data from 20 glacierized and 16 nonglacierized catchments in the Columbia Basin of Canada. The resulting estimates on cryosphere storage contribution to streamflow were well correlated to other regional estimates on the basis of measurements as well as empirical and mechanistic models. Annual cryosphere runoff changed from +19 to −55% during the period 1975–2012, with an average decline of 26%. For August runoff, these changes ranged from +17 to −66%, with an average decrease of 24%. Reduction of cryosphere contributions to annual and late summer flows is expected to continue in the coming decades as glaciers and the perennial snow patches shrink. Our method to isolate changes in late summer cryospheric storage contributions can be used as a first order estimate on changes in glacier contributions to flow and may help researchers and water managers target watersheds for further analysis.
Brahney, J., Menounos, B., Wei, A., Curtis, J.P. (2017). Determining annual cryosphere contributions to stream flow using hydrometric records from southeast British Columbia. Hydrologic Processes 31(8) 1590-1601