Using the Palmer Drought Index, a location is in drought when the Index goes negative, that is, demand for water exceeds the supply.
A drought episode occurs when 10 percent or more of the country is in drought. Of these, 11 covered at least 10 percent of the contiguous United States for 90 percent or more of their duration. The three longest drought episodes, perhaps not surprisingly, took place between July and September s drought , between July and May s Dust Bowl drought , and between June and December early 21st-century drought.
Each of these three drought episodes covered at least 60 percent of the Lower 48 States at their peak and lasted 99 months or longer. The variability of moisture conditions within each drought episode was also examined. Heim found that the early 21st-century drought had a greater spatial variability in moisture conditions than the earlier episodes, meaning there was a greater occurrence of wet areas mixed in with the dry areas. The early 21st-century drought also had a greater variability in month-to-month moisture conditions than the other two, with the s having the smallest monthly variability—in the s, when a region went into drought, it tended to stay in drought longer.
In addition to areal coverage, Heim also looked at the hydrological impacts of the three drought episodes. The event obliterated the widespread belief that the state's many impressive water projects were enough to insulate residents from the threat of water shortages.
By the time relief came from the sky one year later, many of California's reservoirs had been dangerously depleted. In , California once again found itself at the onset of a significant and dangerous shortage of water. According to the California Water Science Center, most of the state's major reservoirs were completed by then, but even that massive human effort proved insufficient.
By , the drought compelled the state to initiate a drought water bank to make water available for sale to the most desperate municipalities. One of the costliest natural disasters in American history and the worst drought on record since the Dust Bowl, it destroyed at least half of the crops on the Great Plains. Florida entered the 21st century in the throes of one of the worst droughts in the state's recorded history. Freshwater withdrawals, record-low stream flows, hundreds of sinkholes, and persistent wildfires defined the crisis, which was particularly bad in the southwest, northeast, and northwest regions of the state.
In March , authorities officially declared the end to more than seven years of severe drought in California. It was a long time coming. For consecutive weeks, Californians suffered a grinding dry spell characterized by dangerously low water reserves, raging fires, the death of million trees on 7 million acres, snowless mountain ranges, and millions of dollars of damage to highways. When the rains finally came, they resulted in a stunning blossom of wildflowers—and raging mudslides.
NOAA outlined causes ranging from decreased precipitation to changes in atmospheric pressure, but the results of the report were clear and undeniable: The drought was the inevitable result of a warming planet.
In , New York suffered one of the worst droughts in the state's history, but it went largely unnoticed compared with the attention given to the drought on the other side of the country. That's because New York wasn't engulfed in the dramatics beamed from California to TV screens worldwide—raging fires, empty reservoirs, and pitched political battles over water rights. In , parts of Alabama received no rainfall at all for six weeks, farmers were selling cattle they could no longer feed, and topsoil had turned to powder.
It was a drought that engulfed much of the Southeast and then spread as far west as Texas and as far north as Kentucky. But it was so hot — oh my gosh, F 42C. I was the first to throw in the white flag and ask to go home — I really hurting. The warming climate is making these dry, hot periods even drier and hotter. And without that moisture, the sun really heats up the ground and the air much faster. But you know, I actually feel kind of optimistic.
In the restaurants and beer houses right now, everybody is talking about the weather, and how hot it is. So actually, if you saw me walking around outside this week, I probably had a smile on my face as I listened to some of these conversations.
A section of Lake Oroville that is normally underwater lies dry and cracked under the California sun. Federal government websites often end in. The site is secure. Drought is a normal climate pattern that has occurred in varying degrees of length, severity, and size throughout history. Tree ring archives indicate that agricultural droughts such as those that happened in the United States during the s Dust Bowl era have occurred occasionally over the last 1, years, and climate model simulations suggest that droughts that may last several years to even decades occur naturally in the southwestern U.
Between and , on average, around 14 percent of the United States was experiencing moderate to severe drought in any given year. While recent droughts and heat waves have made news and broken records in some areas of the United States, by the size of the geographical area affected and the length of time that it persisted, the Dust Bowl era of the s is still the most notable drought and extreme heat event in the U. Scientists have identified 13 major drought episodes—when 10 percent or more of the country is in drought—that affected the United States between and Of these, 11 covered 10 percent or more of the United States excepting Alaska and Hawaii for at least 90 percent of their duration.
The three longest drought episodes occurred between July and May the s Dust Bowl drought , July and September the s drought , and June and December the early 21st-century drought.
Each of these drought episodes covered 60 percent or more of the contiguous United States at its peak and lasted 99 months or longer NCEI ; Heim
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