Possible Impact of Climatic Change and Anomalies to Intensity-Duration-Frequency Curves of Canadian Municipalities and Water Resources of Canadian River Basins

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In recent decades, hydrologic extremes have been occurring more frequently and in greater severity worldwide, including Canada. In the Intergovernmental Panel Climate Change (IPCC) report of 2007, simulations of global climate models unanimously demonstrate that anthropogenic forcing of increased greenhouse gases caused unprecedented temperature rise at global scale in recent decades. As the Earth warms, higher temperatures lead to higher rates of evaporation and precipitation, which will increase the frequency and severity of extreme storms. In designing municipal infrastructures, Intensity-Duration-Frequency (IDF) curves, assumed to be stationary, are used extensively. However, the effect of global warming could modify the intensity of future extreme rainfall events, and so infrastructure design based on existing IDF curves could be under-estimated. Further, IDF curves of most Canadian cities are outdated, for they were developed from single-site analysis of rainfall data and an Extreme Value Type I (EVI) probability distribution calibrated by method of moments (MOM), instead of the General Extreme Value (GEV). The Canadian climate can also be affected by climate anomalies such as El Nino Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO). It has been shown that El Nino lead to very low streamflow anomalies, while La Nina lead to high streamflow anomalies, in western Canada; and that winter precipitation in western Canada are significantly correlated with ENSO and PDO. To address these important issues, we will: (1) Replace obsolete IDF curves of some Canadian cities based on single-site analysis of EVI-MOM, with IDF curves based on multi-site analysis of GEV calibrated by the Probability Weighted Moment method; (2) Develop regional IDF curves using the ensemble empirical mode decomposition method; (3) Simulate potential impact of climate change to the IDF curves of selected Canadian cities by a mesoscale atmospheric model driven with projected climate scenarios of IPCC, first in a stand-alone, then a coupled modes to account for the land-atmospheric feedback; and (4) Assess the combined hydrologic impact of climate change and climate anomalies to some river basins of Canada.