The 2011 Texas Drought: A Briefing Packet for the Texas Legislature

Abstract

The 2011 drought in Texas has been unprecedented in its intensity. The year 2010 had been relatively wet across most of the state, except for extreme eastern Texas. Beginning in October 2010, most of Texas experienced a relatively dry fall and winter, but the record dry March 2011 brought widespread extreme drought conditions to the state. A record dry March through May was followed by a record dry June through August, and the 12-month rainfall total for October 2010 through September 2011 was far below the previous record set in 1956. Average temperatures for June through August were over 2 °F above the previous Texas record and were close to the warmest statewide summer temperatures ever recorded in the United States. As the drought intensified, the previous year’s relatively lush growth dried out, setting the stage for spring wildfires. Conditions were so dry during the spring planting season across much of the state that many crops never emerged from the ground. Continued dry weather through the summer led to increasing hardship for ranchers, who generally saw very little warm-season grass growth while stock tanks dried up. The record warm weather during the summer in Texas was primarily a consequence of the lack of rainfall, but the heat and resulting evaporation further depleted streamflow and reservoir levels. By early fall, trees in central and eastern Texas were showing widespread mortality and dry and windy conditions allowed forest fires to burn intensely and spread rapidly in Bastrop and elsewhere. Twelve-month rainfall was driest on record across much of western, central, and southern Texas, and many stations received less than 25% of their normal 12-month precipitation. The area near, north, and east of Dallas was comparatively well off compared to the rest of the state, but still endured serious drought conditions and record heat. This drought has been the most intense one-year drought in Texas since at least 1895 when statewide weather records begin, and though it is difficult to compare droughts of different durations, it probably already ranks among the five worst droughts overall. The statewide drought index value has surpassed all previous values, and it has been at least forty years since anything close to the severity of the present drought has been experienced across Texas. Because of the return of La Niña conditions in the tropical Pacific, a second year of drought in Texas is likely, which will result in continued drawdown of water supplies. Whether the drought will end after two years or last three years or beyond is impossible to predict with any certainty, but what is known is that Texas is in a period of enhanced drought susceptibility due to global ocean temperature patterns and has been since at least the year 2000. The good news is that these global patterns tend to reverse themselves over time, probably leading to an extended period of wetter weather for Texas, though this may not happen for another three to fifteen years. Looking into the distant future, the safest bet is that global temperatures will continue to increase, causing Texas droughts to be warmer and more strongly affected by evaporation.