The University of Arizona

Background | CLIMAS


Drought lurks constantly at the edges of our lives in the desert Southwest. In a region that supports growing human populations, agriculture, ranching, industry, recreation, and diverse wilderness communities, a sufficient and predictable water supply is crucial. Yet, since Southwestern regions can receive as little as 5 to 15 inches of rain in a normal year, a severe drought often means that humans and ecosystems already coping with a vulnerable water supply do not have sufficient reserves to deal with less precipitation.

All regions of the world are vulnerable to drought. The degree to which the physical environment, animal populations, and human communities can absorb the impacts of drought, however, differs greatly. Different areas of the country can also expect varying frequency of drought. While the Southwestern United States experienced drought 43 percent of the time in a recent 50 year period (1944-1984, defining drought as less than 75 percent of average precipitation), the wetter Northwest only suffered from drought conditions 13 percent of the time (Holechek, et al. 1998). Arizona experienced three severe sustained droughts in the 20th century, one in the 1900s, one in the 1950s, and an ongoing drought that began in the late 1990s. All of these periods of drought were more than mere precipitation deficits; they impacted the ecology, economy, agriculture, and society. Preparing for future drought is vital, since drought is a normal part of the climate of Southwest.

According to the level of drought planning and the economic, social, and political resources available to those impacted, drought can either be seen as a part of the region’s climate or a recurring disaster. Proactive measures—including learning about drought, drafting regional drought plans, and encouraging long-term perspectives on drought mitigation—can stop what climatologists have coined the “Hydro-Illogical Cycle,” a reactionary loop of human response to drought.

Several terms are vital to understanding drought and drought discussion in the Southwest.

Drought  is defined most succinctly as “insufficient water to meet needs” (Redmond 2002), which takes into account a precipitation deficit relative to “normal” levels, and the influence a growing population can have on water demand. For example, a city in New York State could experience a water shortage even without experiencing record-low rain and snowfall, simply because the growing population demands more water than the aquifers can supply. In the Southwest, we experience both extended precipitation deficits and the added stress of growing urban populations. Annually, we draw more water from our aquifers than rain and snowmelt can provide to refill them.

Vulnerability is a term closely tied to the definition of drought above, since it describes the likelihood of an individual or group to experience negative physical or economic impacts due to drought. Vulnerability also depends on the political, social, and economic system in place. Imagine two farmers living in adjacent farms. While they experience the same precipitation deficit, Farmer 1 is able to plan for a drought by investing in non-agricultural sectors, and has insurance. Farmer 2 has bad credit, and recently purchased the farm. Farmer 1 may be able to adapt to the drought, at least in the short term, while we consider Farmer 2 to be highly vulnerable to even short term, mild drought.

Mitigation in this context means attempting to relieve the negative impacts of drought. It also implies planning efforts, and describes efforts to stem or lessen the negative effects of drought by reducing vulnerabilities, rather than belatedly reacting to a drought.

Many people have recognized the need for a comprehensive drought-planning network in the United States. Until recently, however, the drafting and implementation of drought legislation, allocation of funds, and mitigation programs were completed only at regional or state scales and under the discretion of small committees. Many states began calling for a comprehensive system of drought planning, fund allocation, and communication. In 2003, legislators wrote the National Drought Preparedness Act of 2003, draft legislation for a comprehensive national drought policy to be headed by a National Drought Council within the U.S. Department of Agriculture (USDA). Congress has not yet voted on this legislation. Part of the Act establishes a drought assistance fund, administered by the USDA, which would help states mitigate drought impacts and develop drought preparedness programs around the nation. (See more at the Western Governors’ Association.)

The Governor’s Drought Task Force completed the Arizona Drought Preparedness Plan in October 2004. CLIMAS researchers wrote parts of the drought plan and background document, and contributed research and data to Drought Task Force advisory groups.