Streamflow response to climatic variability in a complex mountainous environment: Fraser River Basin, British Columbia, Canada

Abstract Within an area where the regional climate variability signal is apparent, local factors including location, topography and land characteristics affect hydrological response to the signal. Mountainous areas, such as the Western Cordillera in North America, are expected to possess such local effects. The Fraser River Basin in British Columbia, Canada, contains stations with 40 years of precipitation and discharge records from stations widely distributed across the 217 000 km 2 basin. Correlation coefficients were calculated to relate winter precipitation, spring and summer high flow to several climate indices: Pacific Decadal Oscillation (PDO), Pacific‐North American (PNA) and Southern Oscillation Index (SOI). Analyses confirmed that the level of correlation changes during the snowmelt period and does vary locally within the Basin. Correlation of discharge with the indices also changes along the Fraser River, being strengthened or weakened by the influence of its tributaries. These results caution that in hydrologic investigations, (1) even where the region as a whole manifests a strong teleconnection signal, deviation in signal strength within a medium‐sized basin causes local variations in streamflow response to the regional climatic forcing, and (2) the level of correlation attained by streamflow at a basin outlet does not necessarily apply to its tributary sub‐basins. Copyright © 2011 John Wiley & Sons, Ltd.