Drought

What is Drought?
What are the impacts of a drought?
Mitigating Drought
Drought Predictions


 

What is Drought?
According to the National Drought Mitigation Center, a drought is a normal, recurrent feature of climate. Drought is a temporary aberration; it differs from aridity, which is restricted to low rainfall regions and is a permanent feature of climate. Although considered a rare and random event, drought occurs in virtually all-climatic zones.

As an insidious hazard of nature, it originates from a deficiency of precipitation over an extended period of time, usually a season or more.

However, drought should not be viewed as merely a physical phenomenon or natural event. Its impacts on society result from the interplay between a natural event (less precipitation than expected resulting from natural climatic variability) and the demand people place on the water supply.

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What are the impacts of a Drought?
There is a complex web of impacts that spans many sectors of the economy and reaches well beyond the area experiencing physical drought. There are two types of impacts: direct and indirect.

Some examples of direct impacts are reduced crop, rangeland, and forest productivity; increased fire hazard, reduced water levels, and damage to wildlife and fish habitats. Indirect impacts are the consequences of the direct impacts. For example: a reduction crop, rangeland, and forest productivity may result in reduced income for farmers and agribusiness, increased prices for food and timber, unemployment, reduced tax revenues because of reduced expenditures and disaster relief programs.

The impacts of drought can be categorized as economic, environmental, or social. Droughts also bring increased problems with insects and diseases to forests and reduce growth. The incidence of forest and range fires increases substantially during extended droughts, which in turn places both human and wildlife populations at higher levels of risk. Drought is also associated with increases in insect infestations, plant disease, and wind erosion.

Although environmental losses are difficult to quantify, growing public awareness and concern for environmental quality has forced public officials to focus greater attention and resources on these effects.

The social impacts involve public safety, health, conflicts between water users, reduced quality of life, and inequities in the distribution of impacts and disaster relief.

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Mitigating Drought
Taking actions in advance of drought to reduce its long-term risk can involve a wide range of tools. These tools include policies, activities, plans, and programs. On March 20, 3002, Governor Napolitano signed Executive Order 2003-12, establishing the Arizona Drought Task Force. If you would like to participate in Drought Task Force activities, please send and e-mail to dtf@adwr.state.az.us.

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Drought Predictions

According to the National Drought Mitigation Center predicting drought a month or more in advance is complex. Currently, scientists don’t know how to predict drought in advance for most locations. Predicting drought depends on the ability to forecast two fundamental meteorological surface parameters, precipitation and temperature. From the historical record we know that climate in inherently variable. Anomalies of precipitation and temperature may last from several months to several decades.

Studies conducted over the past century have shown that meteorological drought is never the result of a single cause. Global weather patterns have been the topic of research in recent years. These patterns tend to recur periodically with enough frequency and with similar characteristics over a sufficient length of time to offer opportunities to improve the ability for long-range climate prediction. High pressure inhibits cloud formation and results in lower relative humidity and less precipitation. The immediate cause of drought is the predominant sinking motion of air (subsidence) that results in compressional warming or high pressure.

Prolonged droughts occur when large-scale anomalies in the atmospheric circulation patters persist for months or season. It is now known that a major portion of the atmospheric variability that occurs on time scales of months to several years is associated with variations in tropical sea surface temperature.

The potential for improved drought predictions in the near future differs by region, season, and climatic regime. For more information on drought visit the links below:

National Drought Mitigation Center - http://www.drought.unl.edu/index.htm

University of Arizona Institute for the Study of Planet Earth Climate Assessment for the Southwest – www.ispearizona.edu/climas/forecasts/swoutlook.html

2003 Southwest Drought Summit Summary Report – www.mpcer.nau.edu/megadrought/drought_summit_report/index.htm

Arizona Governors Drought Task Force - http://www.water.az.gov/gdtf/

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