You knew it was dry, but how about the driest 17-months ever for Southwest Texas?
“The last 17-months, from April 2005 through August 2006, was the driest period on record,” says Jose Pena, professor and Texas Extension economist at Uvalde.
“As measured in the weather station in Uvalde, only about 14 inches of total rainfall were received, compared to a long-term average of 39.9 inches for the same period,” Pena says.
The current drought does not measure up to the legendary dry spell of the 1950s, for duration and long-term effect. “A quick comparison indicates the drought of the ’50s extended for several years,” Pena says. “Weathermen define a drought as a period when 75 percent or less of the long term annual rainfall is received.”
Data show the 50s drought began in 1948, hovered at close to that 75 percent definition for four years, 1950 through 1954, then skipped 1955 to resume in 1956. “That was the lowest rainfall year of the series with only 9.29 inches of annual rain,” Pena says. The current drought began in 2005.
Pena says the drought of the ’50s hovered at close to the classic drought definition for several years with an average deficit of 35 percent for 84 months (January 1950 through December 1956. The current drought is only 6 percent over an 80-month period (January 2000 through August 2006.
But comparing the worst period of each drought shows rainfall received during the sixteen months from September 1955 through December 1956 averaged 60 percent below long- term average. The deficit during the 17 months from April 2005 through August 2006 averaged 64 percent of normal.
Pena says the drought currently extends over three growth cycles, spring, fall and spring and is entering a third.
“The real effect of any drought is its influence on vegetation and vegetation’s ability to recover,” Pena says. “The vegetation seed or rootstock must survive a drought and must be protected during periods of reduced rainfall.”
Severely reducing grazing pressure is one way to protect vegetation, he says. Recovery also requires abundant, timely rainfall. That occurred during the five years (1956 –1961) following the 1950s drought.
“In addition to reducing stocking rates, we will need above average rainfall for several years to recover from the current drought,” Pena says. “Even then it may be difficult. Rain forecasts appear pessimistic for the short term.”
He says rainfall just before the current drought began was above average and may have encouraged over-grazing, leaving very little vegetative cover into 2006. “Record high temperatures this past summer on bare soil probably weakened rootstocks severely. It may be difficult to recover, even if we have above average rainfall.”
The current drought has prompted cattlemen to liquidate herds and move some animals out of the Southwest to areas with more abundant forage.
“Expansion of the U.S. cattle herd as indicated by the USDA July 12, 2006, mid-year U.S. cattle inventory report may be significantly delayed,” Pena says.