Projected future changes in precipitation and temperature are likely to affect hydrologic processes, such as snow accumulation and melt, evapotranspiration and runoff generation. Therefore, an assessment of climate change impacts on the hydrological cycle is important for long-term water resource management in the province. This project assessed the robustness of results obtained using two fundamentally different approaches to projecting changes in the hydrological cycle.
Methods
The Hydrologic Modelling project used an ensemble of bias-corrected and statistically downscaled global climate model projections (referred to as EGB) of temperature and precipitation. The EGB results were subsequently used to drive the Variable Infiltration Capacity hydrologic model to provide historical and future hydrologic projections (referred to as EGB-HM). In contrast, the Regional Climate Model Diagnostics project analyzed dynamically downscaled raw output from the Canadian Regional Climate Model, driven by multiple runs of the Canadian Coupled Global Climate Model. This ensemble of regional climate model results (referred to as EGR) provided historical and future projections of both climate and hydrology. A comparative analysis of model output from the two approaches was conducted, including a comparison of results for precipitation, temperature, evapotranspiration, snowfall, snow water equivalent and runoff.
Results
Results from the synthesis project validate the work from the Hydrological Modelling and RCM Modelling projects but also revealed some interesting differences between the two approaches. Specifically, monthly precipitation and temperature output of the EGB and EGR methods show appreciable differences in magnitude and range (Figure 1 and Figure 2, respectively). Since EGB output is bias-corrected and scaled to match observations, it corresponds much more closely with observations. These differences in downscaled precipitation and temperature between EGB and EGR are also reflected in future projections.
However, the two approaches project similar changes in the climate and hydrologic variables, namely:
- Temperature is projected to increase in all seasons, with higher increases in winter (Peace) or summer (Upper Columbia).
- Both approaches project increases in precipitation. Seasonally, the output projects higher precipitation increases in autumn, winter and spring, and lower increases (Peace) or decreases (Upper Columbia) in summer.
- Both approaches project an increase in runoff and shifts to an earlier occurrence of spring runoff peaks for both watersheds. Both approaches also project increases in total runoff volumes, which may be accompanied by a decrease in summer runoff in both watersheds. Projected changes for other hydrologic variables are also similar between the two approaches.
Figure 1: EGB and EGR monthly average precipitation in the Peace River watershed for a) baseline (1961-1990) and b) future (2041-2070) periods. Temperature for the baseline period is also compared with observations.
Figure 2: EGB and EGR temperature in the Peace River watershed for a) baseline (1961-1990) and b) future (2041-2070) periods. Precipitation for the baseline period is also compared with observations.
Additional Information
Shrestha, R.R., A.J. Berland, M.A. Schnorbus, A.T. Werner, 2011: Climate Change Impacts on Hydro-Climatic Regimes in the Peace and Columbia Watersheds, British Columbia, Canada. Pacific Climate Impacts Consortium, University of Victoria, Victoria, BC. 37 pp.
Acknowledgements
- BC Hydro
- Biljana Music (Ouranos)
- Marco Braun (UQAM/Ouranos)
- Daniel Caya (Ouranos)