United States, Southwest

Drought Hazards

In general, the climate in the southwest is arid, but mountainous areas also exist in the region. In many areas, the mountains have their own microclimates. Elevated areas capture the winter rains and snows, which provide water for springs and rivers, the largest being the Colorado River.

In most areas of the southwest, aridity is a permanent condition, and dry weather that is severe and prolonged can cause a drought. Droughts turn the forests, brush, and grasslands into very flammable stocks of fuel for wildfires. These may be started by humans, but are often sparked by lightening strikes. The sparse vegetation can be removed by fires, creating burned-over areas denuded of vegetation, leading to rainfall runoff areas that set the stage for destructive floods in the event of heavy rain.

In pre-Columbian times, the Anasazi, the ancient Pueblo builders, developed their culture in the Four Corners region of the southwest (the corners of Arizona, New Mexico, Utah, and Colorado). Carefully using irrigation, their food supply of corn was abundant enough to supply a number of people. However, a prolonged drought between about 1150 and 1300 forced them to abandon their communities and dwellings, like those at Mesa Verde in Colorado or White House Ruins in Canyon de Chelly National Monument in northeast Arizona.

Droughts in modern times have also been known. Periods of extreme heat are common in the southwest, and pose the threat of overexposure. Heat stroke is a potentially deadly threat to people exposed to the sun, even if they are able to drink sufficient quantizes of water. The heat can raise the body temperature to life-threatening levels. These droughts also cause the loss of grazing lands and thus cattle, and force ranchers to buy hay and other feed. One remedy that has been developed is to allow cacti to grow. Prickly pear cactus, with its high water content, is an important water resource for cattle when the sharp, needle-like spines are burned off during drought. Prolonged periods of drought lasting 50–90 years have occurred in the southwest, and could happen again.

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