Quantifying projected changes in runoff variability and flow regimes of the Fraser River Basin, British Columbia

• DOI: 10.5194/hess-23-811-2019
• Publication Date: 2019-02-13T10:28:16Z
• Authors: Siraj Ul Islam; Charles L. Curry; Stephen J. Déry; Francis W. Zwiers
• Keywords: Snowmelt; Pluvial

Abstract. In response to ongoing and future-projected global warming, mid-latitude, nival river basins are expected transition from a snowmelt-dominated flow regime nival–pluvial one with an earlier spring freshet of reduced magnitude. There is, however, rich variation in responses that depends on factors such as the topographic complexity basin strength maritime influences. We illustrate potential effects strong influence by studying future changes cold season variability Fraser River Basin (FRB) British Columbia, large extratropical watershed extending Rocky Mountains Pacific Coast. use process-based hydrological model driven ensemble 21 statistically downscaled simulations Coupled Model Intercomparison Project Phase 5 (CMIP5), following Representative Concentration Pathway 8.5 (RCP 8.5). Warming under RCP leads winter snowfall, shortening average snow accumulation about one-third. Despite this, increases rainfall lead unprecedented peak flows increased overall runoff VIC simulations. Increased is shown be dominant climatic driver Coast Mountains, contributing 60 % mean 2080s. Cold at outlet 70 2080s, its interannual more than doubles when compared 1990s, suggesting substantial challenges for operational forecasting region. Furthermore, almost half (45 %) transitions snow-dominated 1990s primarily rain-dominated according snowmelt pulse detection algorithm. While these projections consistent anticipated hydrologic regime, marked increase FRB likely linked frequent landfalling atmospheric rivers region projected CMIP5 models, providing insights other maritime-influenced basins.