Ground level water resources are the foundation for understanding the consequences of changing climate (temperature and precipitation) at a regional scale. This requires knowledge of the hydrological regime (rain, snow, ice), resources (snowpack, glaciers, reservoirs, lakes, wetlands, groundwater and soil moisture), and processes (interception, evaporation, transpiration, and streamflow). Extremely important water resources responses will result from climate change. Subsequently these responses will influence important economic sectors: power generation, forestry, fisheries, agriculture, mining, and their commercial derivatives.
The objectives of this project were twofold:
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to present an updated analysis of BC's historical climate trends and variability
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to apply projections of future climate using the latest GCM results from the IPCC Fourth Assessment at a coarse scale
Methods
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Document baseline climate information for the 1961-1990 and 1900-2004 periods.
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Examine seasonal climate variability from 1900-2007 and 1950-2005 (ENSO) and 1900-1998 and 1994-2005 (PDO).
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Examine snow water equivalent trends for 1951-2007, 1961-1990 and 1978-2007.
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Examine duration of ice cover across BC for 1966-1995 and 1976-2005.
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Examine climate anomaly projections from CRCM4 forced with CGCM3 and A2 emissions scenarios for annual mean temperature and annual precipitation.
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Project 2009-2050s (2041-2070) high resolution climate projections using PRISM climatology delta method using CGCM3 A2 emissions for annual mean temperature, annual precipitation and mean annual growing degree days.
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Project spring snow water equivalent projection for the 2050s (2041-2070) as an anomaly from the 19621-1990 baseline.
Results
During the past century:
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Positive trends in annual daily minimum, daily maximum temperature, and daily mean temperature have been documented.
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Trends in precipitation were also generally positive.
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Climate variability had a pronounced influence on seasonal temperature and precipitation in BC, especially in the winter and spring seasons.
Historical hydrologic trends and variability include:
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Losses of April 1 snowpack of -25% on average at BC sites and as much as -50% at a few sites over the past 50 years. For shorter record lengths, however, the variability was large and not homogeneous across the province.
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Trends in glacier volume over the 1985-1999 period indicate that many glaciers are out of phase with the current climate.
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Changes in streamflow have occurred throughout BC, but depend on the hydro-climatic region and the streamflow regime.
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Impacts of ENSO and PDO on the seasonal variability of streamflow.
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Decreased duration of lake ice in the most recent records.
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Feedbacks from changing surface groundcover that are already evident in BC forests due to the Mountain Pine Beetle infestation. The ground cover is changing and impacts to hydrology can only be estimated.
Historical hydrologic trends and variability include:
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The average annual temperature in BC is projected using an ensemble of GCMs to be warmer compared to the GCM baseline (1961-1990) climate, and this shift is projected to occur in both winter and summer seasons.
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The average annual precipitation in BC is projected to increase slightly. However, most of this increase is projected to occur in the winter season, while decreases are projected to be in the summer.
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Regional differences from the BC temperature and precipitation projections are evident using the Canadian RCM.
Hydrologic impacts of projected climate change (2050s) include:
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Projected decline in snowpack, especially in the Coastal Mountains of BC.
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Reduction in glacier volume over the 1985-1999 period.
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Reduction of flow in the dry season, and a reduction of flow during the summer months by the 2050s.
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Reduction in soil moisture by the 2040s during the summer and fall for parts of the Columbia Basin.
Additional Information
Rodenhuis, D, K.E. Bennett, A.T. Werner, T.Q. Murdock and D. Bronaugh, 2007 (Revised 2009): "Climate Overview 2007: Hydro-climatology and Future Climate Impacts in British Columbia". Pacific Climate Impacts Consortium, University of Victoria, Victoria, BC. 312pp.
Bennett, K.E., T.Q. Murdock and D.R. Rodenhuis, 2009: "Climate Overview Update and Errata". Pacific Climate Impacts Consortium, University of Victoria, Victoria, BC. pp.16
B.C. Ministry of Environment. 2007. Environmental Trends in British Columbia: 2007: State of Environment Reporting.
D.S. Lemmen, F.J. Warren, J. Lacroix and E. Bush (Editors), 2007: From Impacts to Adaptation: Canada in a Changing Climate 2007, Government of Canada.
Acknowledgements
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BC Hydro
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BC Ministry of Environment