Drought in Canada
Prolonged, large-area droughts are among Canada's costliest natural disasters having major impacts on a wide range of sectors including agriculture, forestry, industry, municipalities, recreation, human health, society and ecosystems.
They frequently stress water availability by depleting soil moisture, reducing stream flows, lowering lake and reservoir levels, and diminishing groundwater supplies.
This ultimately affects several economic activities including for example, decreased agricultural production, less hydro-electric power generation, and increased freshwater transportation costs.
Droughts also create major environmental hazards such as reduced water quality, wetland loss, soil erosion and degradation, and ecological habitat destruction.
Well below normal precipitation was reported in areas of Alberta and Saskatchewan for more than four consecutive years extending from autumn 1999 to spring 2004.
In British Columbia and Manitoba, hydro-electric generation was curtailed, necessitating additional purchases of power from neighboring jurisdictions.
Long-lasting impacts include soil degradation by wind erosion and deterioration of grasslands that could take decades and longer to recover.
High surface temperatures intensify droughts by enhancing evapotranspiration in summer, and increasing sublimation and melting of the snowpack during winter.
During the 20th century, mean annual air temperature has increased by around 1 °C over southern Canada with the greatest warming in the west and the largest rates during winter and spring.
Indices used to measure drought show considerable decadal-scale variability with no long-term trends discernible in any portion of the country.
Over the Canadian Prairies for example, growing season extended dry periods are associated with a persistent atmospheric circulation pattern that includes a large-amplitude ridge centred over the area.
Drought can also be initiated and/or accentuated during winter when a lack of snowfall results in lower than normal spring runoff and thus, reduced stream flow and reservoir and soil moisture replenishment.
This relationship is likely related to feedback processes (such as soil moisture anomalies) that enhance or prolong drought situations (however, more research is required to verify this).
Reasons for the persistence of circulation patterns that lead to drought are not entirely understood but are likely related to surface boundary conditions such as snow and ice cover, vegetation, soil moisture, and sea-surface temperatures (SSTs) that force the climate system through variations in their optical and thermal properties.
These forcing factors directly influence local to regional atmospheric flow which in turn, can affect large-scale circulation over other areas of the globe (known as teleconnections).
The considerable lag between summer moisture and large-scale SSTs provides a basis for developing long-range forecasting of drought conditions in Canada.
The site provides North American maps based on a synthesis of multiple indices and local impacts that best represents current drought conditions.
Drought prediction involves anticipating climatic anomalies that produce unusually dry conditions for an extended period.
Adaptation involves adjusting to climate change, variability, and extremes to avoid or alleviate negative impacts and benefit from opportunities.
Drought adaptation decisions are made at a variety of levels ranging from individuals, to groups and institutions, to local and national governments.
There are various adaptation processes or strategies including sharing and/or bearing the loss, modifying drought effects, research, education, behavioral changes, and avoidance.
Adaptive measures include soil and water conservation, improved irrigation, the construction of infrastructure (wells, pipelines, reservoirs), and the exploration of groundwater supplies.
An assessment of Canadian prairie drought: past, present, and future, Climate Dynamics, Volume 41, Issue 2, pp 501–516 Bonsal, B.R., Chakravarti, A.K.
Teleconnections between north Pacific SST anomalies and growing season extended dry spells on the Canadian Prairies, International Journal of Climatology, 13, 865–878.
Lessons Learned from the Canadian Drought Years of 2001 and 2002: Synthesis Report, Agriculture and Agri-Food Canada, Saskatchewan Research Council Publication No.
