Several scientists at NASA and the state climatologist say the record-setting heat and drought of last summer in Texas was made worse by climate change.
More than just providing bragging rights that Texas now holds the record for hottest summer ever recorded in the United States, that conclusion adds another layer of uncertainty for water planners.
James Hansen of the NASA Goddard Institute for Space Studies and Columbia University's Earth Institute titled his still unpublished climate analysis, "Perceptions of Climate Change: The New Climate Dice."
"We conclude that extreme heat waves, such as that in Texas and Oklahoma in 2011 and Moscow in 2010, were 'caused' by global warming, because their likelihood was negligible prior to the recent rapid global warming," he wrote in the paper that is still undergoing peer review. "We can say with a high degree of confidence that these extreme anomalies were a consequence of global warming."
Some water utilities across the state are still struggling to meet demand because of the drought, which set the record for a single year. But many more are not ready for a repeat of the drought of the 1950s, which lasted seven years and is considered the worst long-term one on record. Adding climate change on top of that will make planning more difficult, as high temperatures mean more evaporation and less water going into rivers, reservoirs and aquifers.
"They don't know what to expect year to year." said Tom Gallier, a former manager of the Bexar Metropolitan Water District who has run water utilities across the West. "That is a scary thought for an industry that specializes in thinking 50 or even 100 years out."
The benchmark for water planning in Texas is the 1950s drought. The San Antonio Water System, Edwards Aquifer Authority and the state use those years to model what is considered the worst-case scenario and then plan accordingly.
The problem is that tree-ring studies, including one of post oaks near San Antonio and another of cypress trees across the state, show more severe droughts have occurred. Climate change is introducing the possibility that droughts will be more extreme.
Last summer is held up as evidence that that is already happening by state climatologist John Nielsen-Gammon and Hansen, who is known for his outspokenness about human-caused emissions becoming the driving force in climate change.
Nielsen-Gammon said he took issue with how Hansen's paper could be interpreted to say that climate change was the only cause of the drought but that there was no doubt that the summer was hotter because of it.
Both scientists agree that the year would have been hot and dry no matter what, but that climate change made it worse.
"In other words, nature made it a record," Nielson-Gammon wrote after reviewing Hansen's paper. "Climate change made it a phenomenal record."
Even as the debate over climate change continues, water planners have to deal with the reality that future droughts are likely to be more severe than in the past 50 years.
But they can't do their job based on speculation, said Chuck Ahrens, SAWS' vice president of water resources.
"The gold standard is still the drought of record because that is what we know," he said.
Ahrens points out San Antonio is uniquely situated between two aquifers and is thus less susceptible to the wilder and more frequent swings of rainfall and temperature that climate change might bring.
The limestone Edwards Aquifer to the north can fill up with just a few good rains, giving the city enough stored water in only a few weeks to last a year.
To help San Antonio make it through multiple dry years, SAWS pumps water into the sand of the Carrizo Aquifer to the south, filling it like an underground reservoir. Neither aquifer loses water to evaporation, like surface reservoirs.
SAWS' water plan shows that it can more than meet demand through 2060 even with a repeat of the drought of record, which is the extent of its planning horizon, according to Darren Thompson, SAWS' manager of water resources.
But other parts of Texas do not have such resources.
Spicewood, outside of Austin, ran out of water because it is dependent on wells drilled into a much less reliable aquifer than the Edwards.
The Lower Colorado River Authority will not provide water to rice farmers in South Texas this year because Lakes Travis and Buchanan are still too low, the first time farmers will be cut off by the LCRA.
Across the Panhandle, reservoirs went dry as increased temperatures accelerated evaporation, and rains have not been enough to refill them.
And that was just from a one-year drought.
The 2012 State Water Plan projects losses of $11.9 billion if a drought similar to the 1950s were to occur and projects in the plan are not funded. The estimated cost rises to $115.7 billion annually by 2060, with more than 1 million jobs lost.
So far, the Legislature has not funded the $53 billion plan, which covers only a quarter of the state's needs over the next 50 years.
