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.
Although most regions of Canada have experienced drought, many of the southern regions of the Canadian Prairies and interior British Columbia are most susceptible. During the past two centuries, at least 40 droughts have occurred in western Canada with multi-year episodes being observed in the 1890s, 1910s, 1930s, 1960s, 1980s, and the early 2000s. Droughts in southern Ontario/Quebec are usually shorter, smaller in area, less frequent, and less intense. Nonetheless, there have been some major drought occurrences there as well during the 20th century. Droughts in the Atlantic Provinces occur even less frequently. Droughts are less of a concern for northern Canada mainly due to their lower population densities. However, increased frequencies of forest fires during drought years can have serious economic impacts. A 2023 report by Agriculture and Agri-Food Canada said that 97% of agricultural landscape in the Prairies was "abnormally dry or experiencing moderate to exceptional drought". [2] In Alberta, there were 51 water shortage advisories in place in December 2023. [2]
Rarely has drought been as serious or extensive as the 1999-2004 episode. [3] This was the worst drought for at least a hundred years in parts of the Canadian Prairies. 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. No single year on record between Medicine Hat, Kindersley, and Saskatoon was drier than in 2001. The years 2001 and 2002 may have also brought the first coast-to-coast droughts on record, and were rare as they struck areas less accustomed to dealing with droughts including parts of Atlantic Canada and the northern agricultural prairies (see Figure 1). Canada's Gross Domestic Product fell $5.8 billion for 2001 and 2002. In addition, previously reliable water supplies such as streams, wetlands, reservoirs, and groundwater were placed under stress and often failed. For example, the number of natural Prairie ponds in May 2002 was the lowest on record while in 2001, Great Lakes-St. Lawrence water levels plunged to their lowest point in more than 30 years, thereby significantly increasing marine transportation costs. In British Columbia and Manitoba, hydro-electric generation was curtailed, necessitating additional purchases of power from neighboring jurisdictions. In 2002, the incidence of forest fires in Alberta increased to five times the ten-year average while in summer 2003, populated regions of interior British Columbia were stricken by drought-enhanced fires. 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. Over the same period, annual precipitation has significantly increased over most of southern Canada with the exception of southern Alberta and Saskatchewan. Coincident with the large increases in spring temperature, the 1980s to the present have been associated with rapid reductions in snow cover during the second half of the snow season. Over the last 30 to 50 years, average stream flow has decreased in many parts of Canada with significant reductions in the south. Great Lakes’ water levels have shown substantial variability during the 20th century with no evidence of a long-term trend. Lower levels coincided with the droughts of the 1930s, early 1960s, and the recent 1999-2001 dry period. Over the Prairies, the numbers and water levels of wetlands have shown no clear trend over the last 40 to 50 years.
Indices used to measure drought show considerable decadal-scale variability with no long-term trends discernible in any portion of the country. Most southern regions of Canada, however, experienced drought conditions during the late 1990s to early 2000s. The worst and most prolonged Canadian Prairie-wide droughts during the instrumental period occurred in the early part of the 20th century (1920s and 1930s). Paleo studies over the southwestern Canadian Prairies using tree ring chronologies dating back to 1597 indicate that the 20th century lacked the prolonged droughts of the 18th and 19th Centuries when droughts were evident for decades at a time.
Although considerable research has been carried out on droughts, there is still no complete theory that explains their formation, persistence, and termination. The major factor in the onset and continuation of drought involves distinctive circulation patterns in the upper atmosphere. 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. This ridge creates ‘blocking conditions’ that displace storm tracks away from 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. Reduced winter precipitation is also caused by persistent atmospheric circulation patterns that involve ridging over the affected area.
Droughts tend to persist. Warm, dry springs are followed by hot, dry summers; warm summers follow other warm summers; and so on. 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). A significant amount of research on drought in Canada has occurred as a part of the Drought Research Initiative, which focused in a comprehensive manner on the 1999-2005 drought in the Canadian Prairies.
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). For Canada, significant relationships between El Niño [4] and La Niña [5] events and winter/spring temperature and precipitation have been determined. In general, El Niño is associated with warmer/drier winters while La Niña has an opposite effect. Linkages between Canadian climate and teleconnections such as the Pacific Decadal Oscillation and the North Atlantic Oscillation are also evident, but mainly during the winter season. Teleconnections during summer are not as strong. However, recent research has shown that some El Niño events are associated with a summer moisture deficit in the western two-thirds of Canada while La Niñas produce an abundance of summer moisture in extreme western Canada. The considerable lag between summer moisture and large-scale SSTs provides a basis for developing long-range forecasting of drought conditions in Canada.
Greater Vancouver has been prone to summer droughts in recent years.
In response to the economic and environmental significance of droughts, scientific concern has been expressed regarding climate change impacts on future drought frequency, duration, and severity over various regions of the globe including Canada. Climate models are projecting considerable increases to temperature and in general, small increases to precipitation over southern Canada. This translates into future increases of summer continental interior drying and associated risk of droughts. The increased drought risk is attributed to a combination of increased temperature and potential evapotranspiration not being balanced by precipitation. Note that considerable uncertainty exists with respect to future precipitation, particularly on a regional basis. Furthermore, there is little consensus regarding future changes to teleconnections and since these patterns have a significant impact on temperature and precipitation over Canada, insight into the relative occurrence of future drought remains a huge knowledge gap.
Numerous indices that measure drought severity are used to monitor drought. These range from those that only consider precipitation, to complex indices that incorporate a water balance approach using precipitation, antecedent soil moisture, potential evapotranspiration, and runoff. For Canada, real-time information on pasture conditions, on-farm surface water supplies, and several drought indices are provided in Agriculture and Agri-Food Canada's Drought Watch [6] web site. The site monitors the risk and status of drought over major agricultural regions of the country and also promotes practices to reduce drought vulnerability. The North American Drought Monitor [7] has been established as a cooperative effort among drought experts in Canada, Mexico, and the U.S. to monitor drought on a weekly basis. 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. Environment Canada produces three-month deterministic temperature and precipitation forecasts for the ensuing 1–3, 2–4, 4–6, 7–9, and 10–12 days periods. The 1-3 and 2-4 month forecasts are based upon an ensemble of 40 model runs. Probabilistic forecasts, which give estimates of the probability that the seasonal mean will be above, near, or below normal are also provided for the 1-3 and 2-4 month periods. Forecasts for 4–6, 7-9 and 10–12 months are produced with a statistical method. The forecasts are updated on a monthly basis and posted on the Environment Canada Seasonal Forecasts Archived 2009-02-10 at the Wayback Machine [8] website.
Adaptation involves adjusting to climate change, variability, and extremes to avoid or alleviate negative impacts and benefit from opportunities. Drought adaptations include short to long-term actions, programs, and policies implemented both during, and in advance of the drought to help reduce risks to human life, property, and productive capacity. Canadians have a great deal of experience in adapting to droughts, however, their strategies vary by sector and location. Areas with greater drought risks are often better prepared to deal with dry conditions. 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. The usefulness of these strategies varies with location, sector, and nature and timing of the drought. Better management responses may be made with improved drought monitoring and advanced prediction. Adjustments that occur after the drought are generally less effective compared to planned anticipatory adaptation.
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A drought is a period of drier-than-normal conditions. A drought can last for days, months or years. Drought often has large impacts on the ecosystems and agriculture of affected regions, and causes harm to the local economy. Annual dry seasons in the tropics significantly increase the chances of a drought developing, with subsequent increased wildfire risks. Heat waves can significantly worsen drought conditions by increasing evapotranspiration. This dries out forests and other vegetation, and increases the amount of fuel for wildfires.
Climatology or climate science is the scientific study of Earth's climate, typically defined as weather conditions averaged over a period of at least 30 years. Climate concerns the atmospheric condition during an extended to indefinite period of time; weather is the condition of the atmosphere during a relative brief period of time. The main topics of research are the study of climate variability, mechanisms of climate changes and modern climate change. This topic of study is regarded as part of the atmospheric sciences and a subdivision of physical geography, which is one of the Earth sciences. Climatology includes some aspects of oceanography and biogeochemistry.
The Madden–Julian oscillation (MJO) is the largest element of the intraseasonal variability in the tropical atmosphere. It was discovered in 1971 by Roland Madden and Paul Julian of the American National Center for Atmospheric Research (NCAR). It is a large-scale coupling between atmospheric circulation and tropical deep atmospheric convection. Unlike a standing pattern like the El Niño–Southern Oscillation (ENSO), the Madden–Julian oscillation is a traveling pattern that propagates eastward, at approximately 4 to 8 m/s, through the atmosphere above the warm parts of the Indian and Pacific oceans. This overall circulation pattern manifests itself most clearly as anomalous rainfall.
The characteristics of United States rainfall climatology differ significantly across the United States and those under United States sovereignty. Summer and early fall bring brief, but frequent thundershowers and tropical cyclones which create a wet summer and drier winter in the eastern Gulf and lower East Coast. During the winter, and spring, Pacific storm systems bring Hawaii and the western United States most of their precipitation. Low pressure systems moving up the East Coast and through the Great Lakes, bring cold season precipitation to from the Midwest to New England, as well as Great Salt Lake. The snow to liquid ratio across the contiguous United States averages 13:1, meaning 13 inches (330 mm) of snow melts down to 1 inch (25 mm) of water.
The Indian Ocean Dipole (IOD), is an irregular oscillation of sea surface temperatures in which the western Indian Ocean becomes alternately warmer and then colder than the eastern part of the ocean.
North Dakota's climate is typical of a continental climate with cold winters and warm-hot summers. The state's location in the Upper Midwest allows it to experience some of the widest variety of weather in the United States, and each of the four seasons has its own distinct characteristics. The eastern half of the state has a humid continental climate with warm to hot, somewhat humid summers and cold, windy winters, while the western half has a semi-arid climate with less precipitation and less humidity but similar temperature profiles. The areas east of the Missouri River get slightly colder winters, while those west of the stream get higher summer daytime temperatures. In general, the diurnal temperature difference is prone to be more significant in the west due to higher elevation and less humidity.
The climate of Argentina varies from region to region, as the vast size of the country and wide variation in altitude make for a wide range of climate types. Summers are the warmest and wettest season in most of Argentina, except for most of Patagonia, where it is the driest season. The climate is warm in the north, cool in the center, and cold in the southern parts, that experience frequent frost and snow. Because the southern parts of the country are moderated by the surrounding oceans, the cold is less intense and prolonged than areas at similar latitudes in the northern hemisphere. Spring and autumn are transition seasons that generally feature mild weather.
The Global Energy and Water Exchanges Project is an international research project and a core project of the World Climate Research Programme (WCRP).
The United States' contiguous western and especially southwestern region has experienced widespread drought since about year 2000. Below normal precipitation leads to drought, and is caused by an above average persistence of high pressure over the affected area. Changes in the track of extratropical cyclones, which can occur during climate cycles such as the El Niño-Southern Oscillation, or ENSO, as well as the North Atlantic Oscillation, Pacific Decadal Oscillation, and Atlantic multidecadal oscillation, modulate which areas are more prone to drought. Increased drought frequency and severity is also expected to be one of the effects of global warming.
Like other parts of the world, climate in Idaho has changed dramatically over the geologic history of the Earth. Paleo-climatic records give some indication of these changes. The longest instrumented records of climate in Idaho extend back to the late 1800s. Concern over human induced climate change through the emission of carbon dioxide from fossil fuels and methane from agriculture and industry, are driving research efforts across the state at university, state, and federals levels to understand what the implications of climate change could be in Idaho.
The Drought Research Initiative (DRI) was established to better understand the characteristics and processes influencing Canadian Prairie droughts and better predict them, focusing on the severe drought which began in 1999 and largely ended in 2005. It is an interdisciplinary effort involving 15 funded investigators from six Canadian universities, over 20 collaborators from other universities and federal laboratories, and partners from three provincial governments. The DRI focuses on five research themes: quantification, understanding, prediction, comparisons with other droughts, and implications for society. Details may be found in Stewart et al. (2008) and on the DRI website.
Droughts are a relatively common feature of the weather in the United Kingdom, with one around every 5–10 years on average. These droughts are usually during the summer, when a blocking high causes hot, dry weather for an extended period. However this means that droughts can vary in their characteristics. All types of drought cause issues across all sectors, with impacts extending to the ecosystem, agriculture and the economy of the whole country in severe cases of drought. The south east of the country usually suffers most, as it has the highest population and the lowest average precipitation per year, which is even lower in a drought. Even in these areas in severe droughts, the definition, impacts, effects and management are all minimal in comparison to drought prone areas such as Australia and parts of the United States. In recent years however, the summers of 2007, 2008, 2009, August 2010 and 2012 were wetter than normal, 2007 being wettest on record. Droughts have continued to occur in recent times, with spring 2011, July 2013, summer 2018, spring 2020, spring and summer 2022 and May and June 2023 all featuring excessively dry periods for part or all of the UK, and will likely become more severe due to climate change over the 21st century.
The 2000s drought in Australia, also known as the millennium drought, is said by some to be the worst drought recorded since European settlement.
The effects of climate change in the Canadian province of Saskatchewan are now being observed in parts of the province. There is evidence of reduction of biomass in Saskatchewan's boreal forests that is linked by researchers to drought-related water stress stemming from global warming, most likely caused by greenhouse gas emissions. While studies, as early as 1988 have shown that climate change will affect agriculture, whether the effects can be mitigated through adaptations of cultivars, or crops, is less clear. Resiliency of ecosystems may decline with large changes in temperature. The provincial government has responded to the threat of climate change by introducing a plan to reduce carbon emissions, "The Saskatchewan Energy and Climate Change Plan", in June 2007.
The 2012–2013 North American drought, an expansion of the 2010–2013 Southern United States drought, originated in the midst of a record-breaking heat wave. Low snowfall amounts in winter, coupled with the intense summer heat from La Niña, caused drought-like conditions to migrate northward from the southern United States, wreaking havoc on crops and water supply. The drought inflicted significant economic ramifications for the affected states. It exceeded, in many measures, the 1988–1989 North American drought, the most recent comparable drought.
The ecology of the Great Plains is diverse, largely owing to their great size. Differences in rainfall, elevation, and latitude create a variety of habitats including short grass, mixed grass, and tall-grass prairies, and riparian ecosystems.
The historical and ongoing droughts in California result from various complex meteorological phenomena, some of which are not fully understood by scientists.
The effects of climate change on the water cycle are profound and have been described as an intensification or a strengthening of the water cycle. This effect has been observed since at least 1980. One example is when heavy rain events become even stronger. The effects of climate change on the water cycle have important negative effects on the availability of freshwater resources, as well as other water reservoirs such as oceans, ice sheets, the atmosphere and soil moisture. The water cycle is essential to life on Earth and plays a large role in the global climate system and ocean circulation. The warming of our planet is expected to be accompanied by changes in the water cycle for various reasons. For example, a warmer atmosphere can contain more water vapor which has effects on evaporation and rainfall.
Effects of the El Niño–Southern Oscillation in Australia are present across most of Australia, particularly the north and the east, and are one of the main climate drivers of the country. Associated with seasonal abnormality in many areas in the world, Australia is one of the continents most affected and experiences extensive droughts alongside considerable wet periods that cause major floods. There exist three phases — El Niño, La Niña, and Neutral, which help to account for the different states of ENSO. Since 1900, there have been 28 El Niño and 19 La Niña events in Australia including the current 2023 El Niño event, which was declared on 17th of September in 2023. The events usually last for 9 to 12 months, but some can persist for two years, though the ENSO cycle generally operates over a time period from one to eight years.
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