   What is Drought? - June 25, 2008 Jeff Schalau, Associate Agent, Agriculture & Natural Resources University of Arizona Cooperative Extension, Yavapai County The word “drought” is commonly used, but do you know what it means? Working on the Yavapai County Local Drought Impact Group (LDIG) has taught me that people always associate drought with water and immediately want to talk about water conservation or limiting new development. There is a definite connection between water supplies and drought but, the LDIG is charged with preparing for, educating people about, monitoring, and mitigating the impacts of drought. It’s a broader view than simple water conservation – it requires a deeper understanding of where we live and how we go about it both as individuals and as a society. Let’s define some key terms and concepts. Climate is the weather, extremes and averages, over a long period of time – the standard time period is 30 years. Drought is a normal, recurrent feature of climate, although many mistakenly consider it a rare and random event. It occurs in virtually all climatic zones, but its characteristics and impacts vary significantly from one region to another. Drought originates from a deficiency of precipitation over an extended period of time, usually a season or more. This deficiency results in a water shortage for some activity, group, or environmental sector. Other climatic factors such as high temperature, high wind, and low relative humidity can increase drought severity. Drought can be further categorized according to severity and impact. A meteorological drought is defined usually on the basis of the degree of dryness when compared to “normal” and the duration of the dry period. A hydrological drought is associated with the effects of periods of precipitation shortfalls on surface or subsurface water supplies. An agricultural drought links various characteristics of meteorological and hydrological drought to agricultural impacts, focusing on precipitation shortages, differences between actual and potential evapotranspiration (the amount of water needed by a given crop), soil water deficits, reduced ground water or reservoir levels, and so forth. In other words: crops are negatively impacted due to lack of precipitation. When we put the drought classifications listed above together with supply and demand related to some economic good, we call it a socioeconomic drought. The supply of many economic goods, such as water, forage for wildlife and livestock, food grains, fish, and hydroelectric power, depends on weather. Because of the natural variability of climate, water supply is ample in some years but unable to meet human and environmental needs in other years. Socioeconomic drought occurs when the demand for an economic good exceeds supply as a result of a weather-related shortfall in water supply. Ultimately, drought is an impact on society that results from the interaction between climate the demands people place on natural resources. Human beings can also aggravate the impact of drought. The Dust Bowl of the 1930s is considered one of the most severe drought events of recent history. In July 1934, about 65% of the United States was in severe to extreme drought and the central great plains were most severely affected. During the Dust Bowl, countless crops and livestock were damaged or destroyed by drought, high temperatures, and high winds, and many people faced severe hardships. But let’s put these impacts into a broader perspective. Prior to the Dust Bowl, new technology and cropping practices were being applied to submarginal farmlands and cultivated acreages were greatly expanded. When that drought period inevitably occurred, it was more devastating because of prior human activities. Locally, the Yavapai County LDIG is working to enlist on-the-ground resource managers and citizen scientists to document site-specific drought impacts though the Yavapai County LDIG. This is part of a larger statewide effort by the University of Arizona Cooperative Extension and the Arizona Department of Water Resources. People interested in learning more about monitoring drought impacts can send me an E-mail at jschalau@ag.arizona.edu. I will share your interest with other members of the Yavapai County LDIG. I’m not discouraging phone calls, but the current lines of communication are for this project all electronic. The University of Arizona Cooperative Extension has publications and information on gardening and pest control. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 ext. 14 or E-mail us at cottonwoodmg@yahoo.com and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/. |