Modelling climate change impacts in the Peace and Athabasca catchment and delta: I - hydrological model application

The Peace-Athabasca Delta (PAD) is an extensive freshwater delta fed by the confluence of the Peace and Athabasca rivers. The Peace River, with regulation at the W.A.C. Bennett Dam, has a direct influence on the hydrology and eco-hydrology of the PAD. To investigate the relative roles of climate variability and flow regulation, the Peace and Athabasca watershed and delta were simulated using a distributed hydrologic model, WATFLOOD. The model was forced using historical, station-observed data as well as climate change scenario temperature and precipitation data. The modelled hydrographs over the 24-year simulation period were compared with measured values at the 14 streamflow stations with generally good agreement for volume and timing of flow, monthly estimates having a Nash-Sutcliffe (R-2) of 0.76 and 0.72 for the Peace and Athabasca Rivers, respectively. However, the total of the monthly runoff estimates were positively biased by 19% and 29%, respectively (Peace River at Peace Point, D-v = 19%, Athabasca River at Ft. McMurray D-v = 29%). A comparison between estimated current and future climate scenarios revealed a significant shift towards an earlier melt season as well as elevated winter flows for both river systems. The uniform application of temperature and precipitation change yields a non-uniform response. The lower elevations of the Athabasca system show trends towards increased streamflow volumes; however, the higher elevations of the Peace River system may experience increased evaporative flux which will more fully compensate for higher precipitation resulting in only slightly increased streamflow under changed climate. The degree and direction of estimated change in streamflow are heavily dependant on the climate change scenario. Copyright (c) 2006 Crown in the right of Canada, and John Wiley & Sons. Ltd.