Drought is an extended period of abnormally dry weather that lasts long enough to result in water shortages, dry soil, and crop damage. During a drought, there is an increased risk of wildfires and dust storms. Drought is caused by a lack of rain or snow and can also be affected by the natural and man-made environment and local demand for water. Drought can be aggravated by urban sprawl and development created without regard to water supplies and systems.
Drought can last from one season to several decades and can affect up to millions of square miles of land. It can have economic, public health, and environmental impacts.
Drought results in less water for irrigating and watering crops, which in turn may cause crop failures, job losses, and economic hardship for farmers. The quality, amount, and price of food may be affected by drought. The timber, ranching, shipping, boating, and fishing industries may also be affected by drought conditions, including wildfires and lower water levels in lakes and streams. Hydroelectric power may become more scarce and expensive. Because water is required for heating and cooling systems to work, water shortages may cause heat, ventilation, and air conditioning systems to malfunction.
Lower water levels in lakes, rivers, streams, groundwater, and aquifers may compromise the amount and quality of drinking water during a drought. Conditions may also increase the bacteria that lead to algae blooms, which can release airborne toxins. When bodies of water shrink in a drought, they become more stagnant and will then be more favorable for mosquitos, particularly those that harbor West Nile Virus.
Severe drought conditions can also affect air quality. Particulate matter from dry conditions, wildfires, and dust storms can irritate human respiratory systems.
Care should be used with pesticides in drought conditions. Dry forms of pesticides can stay dry and be blown by the wind. These pesticides can accumulate and be washed away in concentrated amounts when the drought ends.
Drought may cause an increase in infectious diseases, including Valley Fever, which is caused by fungal spores in desert soil. It can also increase diseases resulting from bacteria in drinking water, food, and stagnant water. Water-based recreational activities may expose people to waterborne diseases because of bacteria in shallow warm waters. An extended drought followed by heavy snow and rains in the Southwest in 2012 resulted in more deer mice and thus, an increase in human cases of Hantavirus from exposure to these pests.
Drought conditions may pose more serious risks for children, pregnant women, and older adults. Also at higher risk may be people with chronic conditions such as asthma and immune disorders, and people who depend on drinking water from private wells.
Food and habitat for plants and wildlife may be damaged or destroyed during a drought. Drought may increase stress on endangered species, wetlands, and soil quality. Animals and pests, such as snakes, spiders, and bears, may change habitat to find more food, thus coming into contact with humans more often.
Drought is one of the effects and indicators of climate change. Changes in the earth’s temperature will likely increase the severity of future droughts as heat waves become more common, and more moisture evaporates from land and water. Scientists believe that climate change is likely to cause severe drought in parts of the United States, especially the Southwest, during this century.
The most well-known U.S. drought was the Dust Bowl drought of the 1930s, when 65 percent of the country was affected by severe or extreme drought. In the summer of 2012, 55 percent of the continental United States experienced moderate to extreme drought, which was the largest such area since 1956.