by KATE GALBRAITH
Groundwater levels in Texas’ major aquifers dropped considerably between 2010 and 2011, as the state’s drought intensified, according to a report published recently by the Texas Water Development Board.
Hays portion of Trinity was not immune from drought’s grip
WIMBERLEY — During the intense statewide drought of 2010-2011, the portion of the Trinity Aquifer underneath western Hays County dropped a median of 12½ feet as measured at three Wimberley and Dripping Springs area wells monitored electronically by the Texas Water Development Board.
The Central Texas Trinity Aquifer, underlying all or part of 11 counties from Burnet to Bandera, suffered more than any of the state’s eight other major aquifers, according to a technical report compiled earlier this year by state geologists. Thirty-three monitor wells recorded a median drop of 16.7 feet and an average decline of 19.7 feet in 2010-2011.
In Hays County, the drought’s impact on the Trinity was relatively slight in 2010, with two Wimberley area wells dropping an average of 1½ feet. During that same period, the water table as measured in the Glen Rose formation of the aquifer nearer to Dripping Springs rose 18.94 feet.
In 2011, however, the Glen Rose monitor well (charmingly named SWN 57-55-607) recorded an aquifer drop of 31.42 feet, a figure in part skewed by the previous year’s increase. But the two other TWDB wells in Hays County also foretold significant declines — a 8.47 feet drop at SWN-63-705 and 12.51 feet drop at SWN-57-64-705 in the Cow Creek formation of the aquifer.
Even considering the Glen Rose well’s water level rise in 2010, the aquifer overall dropped a little more than six feet between 2009 and the end of 2011, as measured by the three TWDB wells.
The water development board began monitoring the Hays County portion of the Trinity Aquifer in 1997 with the Cow Creek well; since then, the Trinity has dropped 24.64 feet at that location. The aquifer has declined 19.65 feet since TWDB monitoring began at the Glen Rose well in 2006 and 8.95 feet since 2002 at its third Hays County monitoring well in the southwestern corner of the county.
The report showed significant declines in the Ogallala Aquifer, which underlies much of the Panhandle. The water board monitors 26 wells in the Ogallala, and water levels dropped in all but one during the 2010-11 period. The average drop was 3.5 feet, with a median decline of 1.8 feet.
“This year of a drought — it has affected even the groundwater levels to a greater extent than I’ve ever seen,” said Janie Hopkins, who manages the water board’s groundwater division.
The figures for 2011-12, which will probably be ready for publication around August, are also expected to be gloomy. There will probably be a “continuing downward [trend] in the majority of these wells, but just at a less rapid rate,” Hopkins said.
The situation is clearly serious in Texas, where 99 percent of the state is abnormally dry or worse, with 10 percent experiencing exceptional drought. Gov. Rick Perry and other top policymakers have pushed the Legislature to allocate $2 billion to a special fund for water-supply projects, but those efforts are in limbo after a key bill in the Texas House was shelved Monday.
According to the report, the greatest decline during 2010-11 occurred in the Trinity Aquifer of Central Texas, where 33 monitor wells showed a median drop of 16.7 feet, and an average drop of 19.7 feet. (The water board also includes one well in the Edwards-Trinity Plateau in that calculation.)
In South Texas’ Carrizo-Wilcox Aquifer, median water levels of the monitor wells dropped by 4.4 feet in 2010-11, with average declines of 17.1 feet.
In discussing the Carrizo-Wilcox, the water board noted: “Irrigation pumpage during the drought has increased substantially in the Wintergarden area of [south-central] Texas, particularly Zavala, Wilson, and Atascosa counties. Pumping of groundwater has also increased to support oil and gas exploration and production activities related to the Eagle Ford Shale.”
A Carrizo Aquifer well in nearby LaSalle County showed the greatest change for a single well since 2003, dropping some 136 feet.
Some aquifers rebound with good rain, Hopkins noted.
To understand what the drops really mean, it helps to look at an individual well’s overall depth and rate of change. In the Ogallala, for example, a well in Hansford County contained water at around 70-f00t depths in 1950. Now pumpers hit water at 150 feet, and the well’s overall depth is 185 feet.
Some Ogallala wells show similar declines; others are holding relatively steady, reflecting that geologic and topographic conditions can differ considerably by well.
“You can have lots of variability within a short distance,” Hopkins said. She cited the “heterogeneity of the rocks, even with one formation.”
One Ogallala well used in the water board’s research went dry about 18 months ago, she said.
To check the real-time levels of the water board’s monitor wells, click here. Hopkins said that the agency, which has experienced budget-tightening like the rest of the state, has had no funding for equipment such as well recorders or transmitters for the past few years, though local groundwater conservation districts often provide such funds. More funding would also potentially allow the water board to publish groundwater reports in a more timely fashion, she said.
KATE GALBRAITH reports for The Texas Tribune where this story was originally published. It is reprinted here through a news partnership between the Tribune and the San Marcos Mercury.