Modelling climate change impacts in the Peace and Athabasca catchment and delta: III - integrated model assessment

This study utilized the hydrodynamic model, ONE-D, coupled to the distributed hydrological model WATFLOOD, to evaluate the potential effects of a shift in climate on the hydrological regimes of three large lakes (Athabasca, Claire, and Mamawi), and two important sources of inflow (the Peace and Athabasca rivers) in the Peace-Athabasca Delta (PAD). The coupled WATFLOOD/ONE-D system was forced by current climatology and downscaled climate change scenarios from five selected general circulation models (GCMs). Under the selected climate change scenarios, water levels in Lakes Athabasca, Claire, and Mamawi peaked, on average, 40-50 days earlier than at present. Some GCM scenarios predicted an increase in peak lake levels while others predicted suppressed lake levels. Inter-annual water level variability was also sensitive to predicted changes in precipitation and temperature, increasing in winter and decreasing in summer. Water level fluctuations in the major input rivers of the PAD were found to be more variable under the climate change simulations. Moreover, spring freshet peaks were estimated to occur earlier (20-30 days) and to be considerably reduced (up to 1.0 m reductions). Although the simulations converged towards the same general results in seasonality shift, flow level amplitude was GCM-dependent. Simple downscaling methods may well be too coarse to adequately address the important spatial variations that can occur in the long-term climate signal. It is therefore important to understand the sensitivity of this regime to local climatic influences to produce more reliable, quantitative results. An ensemble of approaches that provide meaningfully downscaled results should be considered to confirm the results presented. Copyright (c) 2006 Crown in the right of Canada, and John Wiley & Sons, Ltd.