The main objective of the Hydrologic Modelling project was to estimate the hydrologic impacts of future climate change on select BC watersheds. Hydroelectricity is the largest source of electric power generation in the province and much of it is generated by BC Hydro in the Peace and Columbia River systems. To assess the hydrologic impacts of climate change a high-resolution, physically-based macro-scale hydrologic model was applied within the Peace, Campbell and Upper Columbia watersheds in British Columbia (Figure 1). These three watersheds contain numerous important BC Hydro facilities for hydroelectric generation and represent a range of hydro-climatic regimes. Streamflow projections were made for several locations within the study areas, corresponding to current BC Hydro facilities, potential sites for future hydroelectric development, and several natural drainages.
Methods
This study used a set of eight global climate models (GCMs) driven by three SRES emissions scenarios, intended to capture a range of high, medium and low projected greenhouse gas concentration increases and to project a wide range of potential climate responses for the 2050s (2041-2070) period. GCM results were statistically downscaled and used to drive the Variable Infiltration Capacity (VIC) hydrology model at high spatial resolution. This methodology of selecting multiple GCMs coupled to three emissions scenarios covers a wide range of potential future climates for BC and explicitly addresses both emissions and GCM uncertainty in the final hydrologic projections.
Results
Projected climate and hydrologic results for the three watersheds are summarized below:
- All projections indicate higher temperatures in all seasons and all study areas by the 2050s, with strong agreement across GCMs and emissions scenarios.
- Precipitation projections are less robust for the 2050s (i.e., the range of individual GCM projections includes both positive and negative changes), but suggest increased precipitation in the winter, spring and fall for all study areas under all emissions scenarios.
- Annual discharge in the Peace River and Upper Columbia study areas is projected to increase at the majority of locations studied for all emissions scenarios. Annual discharge changes for the Campbell River study area are expected to be negligible.
- Monthly streamflow projections for locations on the Upper Columbia show a consistent trend towards higher future discharge during fall and winter, an earlier onset of spring melt, and reduced discharge during late summer and early fall (Figure 2). Changes in the timing and duration of the spring melt result in the largest absolute changes in monthly discharge. Differences in the monthly discharge response between the three emissions scenarios are negligible. Monthly streamflow projections for the Peace River are similar.
- Monthly streamflow projections for the Campbell River study area show a strong shift in seasonality due to a transition from a hybrid rainfall-snowmelt regime to an almost exclusive rainfall regime (Figure 3). This transition is expected to result in large increases in fall and winter discharge, and decreases in spring, summer, and early fall discharge, including a longer and more severe low flow period.
Figure 1: Map of British Columbia showing major river systems as well as the PCIC study areas on the Peace River (tan), Upper Columbia River (blue) and Campbell River (green).
Figure 2: Hydrographs showing median monthly discharge rates for the Upper Columbia River at Mica Dam. The black line shows the modelled historical pattern of streamflow while the blue line represents the median discharge for all models and emissions scenarios used in the study. The blue shaded areas illustrate the range of results from the various models and emissions scenarios used. The bottom graph shows the same results as the top graph but presents them as a change in discharge rate compared to the baseline period.
Figure 3: Hydrographs showing median monthly discharge rates for the Campbell River at Strathcona Dam. The black line shows the modelled historical pattern of streamflow while the blue line represents the median discharge for all models and emissions scenarios used in the study. The blue shaded areas illustrate the range of results from the various global climate models and emissions scenarios used. The bottom graph shows the same results as the top graph but presents them as a change in discharge rate compared to the baseline period.
Additional Information
Werner, A.T., 2011. BCSD Downscaled Transient Climate Projections for Eight Select GCMs over British Columbia, Canada. Pacific Climate Impacts Consortium, University of Victoria, Victoria, BC, 63 pp.
Schnorbus, M.A., K.E. Bennett, A.T. Werner and A.J. Berland, 2011. Hydrologic Impacts of Climate Change in the Peace, Campbell and Columbia Watersheds, British Columbia, Canada. Pacific Climate Impacts Consortium, University of Victoria, Victoria, BC. 157 pp.
Zwiers, F.W., M. Schnorbus and G. Maruszeczka, 2011. Hydrologic Impacts of Climate Change on BC Water Resources: Summary Report for the Campbell, Columbia and Peace River Watersheds. Pacific Climate Impacts Consortium, University of Victoria, Victoria, BC. 17 pp.
Acknowledgements
- BC Hydro
- BC Ministry of Environment