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Climate Change Will Alter Patterns of Water Supply

Evidence shows that our climate has changed over the past 50 to 100 years. The average annual temperatures have warmed in different regions of the province and B.C. has lost up to 50% of its snow pack. Total annual precipitation has increased by about 20%. These observed changes have affected our natural resources and many people’s livelihood:

  • Faster melts and increased precipitation have resulted in floods in the Fraser Valley, Interior and throughout British Columbia;
  • Warmer winters have resulted in the mountain pine beetle epidemic which has destroyed an area of pine forest equivalent to four times the size of Vancouver Island;
  • Communities have been experiencing longer summer droughts as weather patterns grow increasingly erratic.

Current projections indicate that B.C. could experience a further warming by 2050. Predicted average temperatures will be warmer in the summer and winter for most of the province, while average rainfall will be higher in the winter and much less in the summer for the southern part of the province (Figures 1,2,3 and 4). As a result, stream flow patterns will be affected. The rain that replenishes our streams, lakes and reservoirs in the winter and spring may fall within a short period in the winter and not later in the year when we need this water to irrigate crops and for other important uses (Figure 5). Predicted effects include:

  • While agriculture may enjoy longer, warmer growing seasons, more frequent and prolonged droughts as well as increased pest infestations are expected;
  • Many areas will experience growing water shortages and increased competition among water uses, including municipalities, irrigation, industry, power generation, fisheries, recreation and aquatic ecosystems;
  • The greater frequency and intensity of extreme weather events and related hazards, such as flooding and forest fires, will threaten key infrastructure (e.g., roads, ports) affecting B.C. communities and people’s health and well-being;
  • Sea levels are expected to rise on the north coast of British Columbia;
  • The mountain pine beetle could expand its range to the north and east, with economic and environmental consequences for the forest industry, communities and ecosystems;
  • Already stressed fisheries will face further challenges, in particular the highly important Pacific salmon species, which are sensitive to stream and ocean surface warming (LiveSmart BC website).

Where can you learn more?

Pike, R/.G., Spittlehouse, D.L., Bennett, K.E., Egginton, V.N., Tschaplinski, P.J., Murdock, T.Q., and Werner, A.T. Climate Change and Watershed Hydrology: Part II – Hydrologic Implications for British Columbia. 2008. Streamline Watershed Management Bulletin, Vol. 11/No. 2 Spring 2008

B.C. Ministry of Environment, Climate Action Secretariat, Live Smart BC website
http://www.livesmartbc.ca/learn/effects.html

B.C. Ministry of Forests and Range, Research Branch. Climate Change website http://www.for.gov.bc.ca/hre/topics/climate.htm

Pacific Climate Impacts Consortium 2007. Climate Overview 2007: Hydro-climatology and Future Climate Impacts in British Columbia.  URL: http://pacificclimate.org/docs/publications/PCIC.ClimateOverview.Revised.March2009.pdf.

Rodenhuis, D., Bennerr, K.E., Werner, A. Murdock, T.Q., and Bronaugh, D. 2007. Hydro-climatology and future climate impacts in British Columbia. Pacific Climate Impacts Consortium. URL: http://www.pacificclimate.org/docs/publications/PCIC.ClimateOverview.pdf

Stewart, I.T., D.R. Cayan, and Dettinger, M.D. 2004. Changes in snowmelt runoff timing in western North America under a “business as usual” climate change scenario. Climatic Change 62:217–232. URL: http://meteora.ucsd.edu/~meyer/stewart_clch.pdf

Thompson, J. 2007. Running dry: Where will the west get its water? Pacific Northwest Research Institute, Science Findings, Issue 97, October 2007. URL: http://www.fs.fed.us/pnw/sciencef/scifi97.pdf

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Hydrologic implications of climate change for B.C.i are profound and include:

  • changes in seasonal precipitation (summers in southern and central B.C. are expected to be drier while northern B.C. will be wetter; winters will be generally wetter across the province);ii
  • increased precipitation intensity, increased magnitude of storm events, and reduced return period of extreme events;
  • increased stream/lake temperatures;
  • increased evaporative demand of the atmosphere, and altered vegetation composition affecting evaporation and interception;
  • decreased snow accumulation, and earlier, accelerated snowmelt;iii
  • less water storage from spring freshet flowsiv and reduced infiltration to recharge ground water supplies;
  • altered timing and magnitude of streamflow (peak flows, low, flowsv; and,
  • accelerated melting of permafrost, lake ice, and river ice.
  • i  Pike, R/.G., Spittlehouse, D.L., Bennett, K.E., Egginton, V.N., Tschaplinski, P.J., Murdock, T.Q., and Werner, A.T. Climate Change and Watershed Hydrology: Part II – Hydrologic Implications for British Columbia. 2008. Streamline Watershed Management Bulletin, Vol. 11/No. 2 Spring 2008
  • ii B.C. Ministry of Forests and Range, Research Branch. Climate Change website http://www.for.gov.bc.ca/hre/topics/climate.htm
  • iii Rodenhuis, D., Bennerr, K.E., Werner, A. Murdock, T.Q., and Bronaugh, D. 2007. Hydro-climatology and future climate impacts in British Columbia. Pacific Climate Impacts Consortium. URL: http://www.pacificclimate.org/docs/publications/PCIC.ClimateOverview.pdf
  • iv Stewart, I.T., D.R. Cayan, and Dettinger, M.D. 2004. Changes in snowmelt runoff timing in western North America under a “business as usual” climate change scenario. Climatic Change 62:217–232. URL: http://meteora.ucsd.edu/~meyer/stewart_clch.pdf
  • v Thompson, J. 2007. Running dry: Where will the west get its water? Pacific Northwest Research Institute, Science Findings, Issue 97, October 2007. URL: http://www.fs.fed.us/pnw/sciencef/scifi97.pdf