Influence of Pacific Climate Patterns on Low-Flows in British Columbia and Yukon, Canada

Abstract

This study investigated the low-flow response (low-flow frequencies, magnitudes and locations) of rivers in British Columbia and Yukon, Canada to the Pacific Decadal Oscillation (PDO) and the El Niño/Southern Oscillation (ENSO). Using stream discharge data from four hydrometric stations in each of four regions of BC (Southern Coast, Southern Interior, Northern Coast and Northern Interior) and the southern Yukon, coherent responses of low streamflows to PDO and ENSO were identified and examined. Low streamflows were defined as flows less than the 10th percentile on a given day compared to the historical streamflow series for that day. It was found that PDO and ENSO both influenced low streamflows in all study regions except Yukon. The PDO signal influenced low-flows more significantly and consistently than the ENSO signal. However, the PDO signal was modulated by ENSO, either strengthening or weakening low-flows depending on geographic location. ENSO had inconsistent impacts on low-flows with large differences between geographic areas. At the study watersheds in BC, correlation analysis showed that 14 and 13 of the 16 rivers showed significant associations between PDO index and low-flow frequencies and low-flow magnitudes, respectively. Temporal location of low-flow is affected by PDO in coastal BC but not in the interior and Yukon. None of the rivers in Yukon showed significant correlations between low-flows and Pacific climate patterns.