Years of Drought Variability in the Central United States

Drought is one of the most damaging climaterelated hazards to impact societies. Although drought is a naturally occurring phenomenon throughout most parts of the world, its effects have tremendous consequences for the physical, economic, social, and political elements of our environment. Droughts impact both surface and groundwater resources and can lead to reductions in water supply, diminished water quality, crop failure, reduced range productivity, diminished power generation, disturbed riparian habitats, and suspended recreation activities, as well as a host of other associated economic and social activities (Riebsame et al. 1991). The droughts of the 1930s, 1950s, and 1980s caused great economic and societal losses in the Great Plains of the United States, a region particularly prone to drought (Karl and Koscielny 1982; Diaz 1983; Karl 1983) (Fig. 1). This area shows signs of becoming increasingly vulnerable to drought because of factors such as the increase in cultivation of marginal lands and the escalated use of groundwater from the Ogallala Aquifer, where water withdrawal has exceeded recharge for many years (Glantz 1989; White and Kromm 1987). Estimates for the return intervals for a Great Plains drought of 1930s duration and intensity, based on the properties of the twentieth-century record, vary from 75 to 3000 years (Bowden et al. 1981; Yevjevich 1967). Estimates of this type do not provide a very clear understanding of how rare the severe droughts of the twentieth century were in the context of the last 2000 years, nor whether drought of even greater magnitude is possible. Paleoclimatic data offer a way to evaluate the severity, duration, and extent of twentieth-century 2000 Years of Drought Variability in the Central United States