Anthropogenic Influence on Multi-Decadal Changes in Hydrology of Western Canada

Thursday, 18 December 2014
Mohammad Reza Najafi1, Sanjiv Kumar1, Francis W Zwiers1, Nathan P Gillett2, Markus Schnorbus1, Alex J Cannon1, Rajesh Shrestha1 and Arelia T Werner1, (1)University of Victoria, Victoria, BC, Canada, (2)CCCma, Victoria, BC, Canada
In this study observed and simulated changes in the hydrology of four western Canadian watersheds are investigated for a possible anthropogenic influence. This analysis was performed over the period of 1950-2012 and for the Fraser, Peace, upper Columbia and Campbell River basins, which represent a range of distinct hydrologic characteristics. Four indicators are used to assess hydrologic change in this region, including minimum temperature, maximum snow water equivalent normalized by total annual runoff, total June-July-August (JJA) runoff normalized by mean annual precipitation, and river flow center of timing. The Coupled Model Intercomparison project Phase 5 (CMIP5) climate simulations are used to quantify climate internal variability as well as climatic responses to different forcing agents, including solar variation, volcanic eruptions, greenhouse gases, sulfate aerosols and other anthropogenic forcings. In order to estimate the hydrologic responses to these forcings the process based, semi-distributed Variable Infiltration Capacity (VIC) hydrologic model is calibrated based on observational records and then driven by downscaled CMIP5 data. Analysis of the trends of the hydro-climatic indicators showed that during recent decades, temperature has significantly increased in western Canada, while the normalized maximum SWE as well as normalized JJA runoff have significantly decreased, indicating a decreasing snow contribution to runoff and increasing evapotranspiration. River flow center of timing also shows a declining trend.