![]() Recent Droughts and the Arid Regions of the United States ![]() Let’s look at the past few hundred years first and then explore the region’s climate in geological time. ![]() The past 150 years, which we have used as our baseline for assumptions about rainfall patterns, water availability for agriculture, water laws, and infrastructure planning, may in fact be an unusually wet period. These earlier Americans are a warning to us. Long dry stretches during the Medieval centuries (especially between 9 CE) had dramatic effects on the native peoples of the Southwest (the ancestral Pueblo, Hohokam, and Sinagua), including civilizational collapse, violence, malnutrition, and forced social dislocation. Southwest when it comes to rain?Īnd with a growing and more urban population and an ever-changing climate, will we ever be free from the threat of long dry periods, with their disruptive effects on food production and the plants and animals that rely on water to survive?Ī glance into the history of the Southwest reminds us that the climate and rainfall patterns have varied tremendously over time, with stretches of drought many decades longer than the one we are experiencing now. The question on everyone’s mind is when will this dry period finally come to an end and rainfall return to normal-and just what is normal for the U.S. As California dries up, food prices might well rise across the nation. Over the past year, 410,000 acres have been fallowed in this vast agricultural region that provides 30 percent of all the produce grown in the United States and virtually all of the world’s almonds, walnuts, and pistachios. The amount of water transported through irrigation systems to California’s Central Valley-the most productive agricultural region in the world-has been reduced to only 20 percent of customary quantities, forcing farmers to deepen groundwater wells and drill new ones. Elsewhere in the Southwest, Lake Powell, the largest reservoir on the Colorado River, is at 44 percent of capacity. In California, reservoirs are currently at only 38 percent of capacity, and the snowpack is only 25 percent of normal for late January. Lake Powell, in 2009, showing a white calcium carbonate “bathtub ring” exposed after a decade of drought lowered the level of the reservoir to 60 percent of its capacity. Drought can lead to failed crops, desiccated landscapes, wildfires, dehydrated livestock, and in severe cases, water wars, famine, and mass migration.Īlthough the situation in the West has not yet reached such epic proportions, the fear is that if it continues much longer, it could. But this bland definition belies the devastation wrought by these natural disasters. Meteorologists define drought as an abnormally long period of insufficient rainfall adversely affecting growing or living conditions. This long drought has crept up on the region, partly because droughts encroach slowly and they lack the visual and visceral effects of other, more immediate natural disasters such as earthquakes, floods, or tsunamis. The southwestern states are also experiencing moderate to severe drought, and this comes on the heels of a very dry decade. A relatively wet December has given way to the driest January on record, and currently over 90 percent of California is in severe to exceptional drought. The majority of water in the western United States is delivered by winter storms from the Pacific, and over the past year, those storms were largely blocked by an enormous ridge of high pressure. The state of California is beginning its fourth year of a serious drought, with no end in sight.
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