Mon October 14, 2013
A Tiny Bit of Vegetable Oil Could Save Texas Billions of Gallons of Water
Originally published on Mon October 14, 2013 3:58 pm
Parts of Central Texas saw as much as 12 inches of rain over the weekend. Water levels in the Highland Lakes rose slightly, but the storm was far from a drought-buster.
Lakes Travis and Buchanan remain only about one-third full.
As the historic drought drags on, water planners are scrambling to find new supplies and conserve the ones we have. But one of the biggest things affecting water supplies in a hot, dry state like Texas is evaporation. On average, the Highland Lakes lose as much water to evaporation as the city of Austin uses each year. Every year, Texas loses the equivalent of five full Lake Travises to evaporation.
So can you do anything about it? Actually, yes.
There are two approaches. First, you can pump the surface water underground. Places like San Antonio are trying that.
“Effectively, they’re using the aquifer system to do the storage and eliminating evaporation altogether,” says David Maidment, a civil engineering professor at the University of Texas at Austin. But you need a bunch of space in a certain kind of aquifer to do it and there’s no guarantee that you’ll get the water back once you put it down there.
The second approach is something called a monolayer.
“Monolayer is a material which is extracted from vegetable oil,” says Moshe Alamaro, a researcher at MIT. He’s done a lot of work with monolayers. The material is a liquid that “when you place it on water, [it] spreads spontaneously and creates a film, the width of which is literally one molecule.”
The monolayer acts as kind of a lid – floating on the surface – to keep the water from evaporating. At one molecule thick, it’s almost imperceptible.
“You cannot see it. You cannot smell it. You cannot taste it,” claims Alamaro.
If you drive a boat through it or swim in it, tearing the monolayer, it will repair itself. As for wildlife, Alamaro points to a study done by Texas A&M where they used two ducks. One was fed the monolayer material every day, the other was not.
“The duck which was not fed with monolayer died two months before the end of the experiment,” says Alamaro. That’s kind of inconclusive, but other studies have found minimal ecological effects, too.
But what about the real test: does it save water? Alamaro says a monolayer on a reservoir can reduce evaporation by as much as 75 percent.
“In California and Texas, the evaporation suppression on existing reservoir can add 4 million acre-feet [of] capacity per year,” says Alamaro. That’s about four times the capacity of Lake Travis.
The idea of monolayers has actually been around for decades.
In fact, in the mid-1960s, the U.S. Bureau of Reclamation studied their use on Lake Hefner, a 2,500 acre reservoir outside of Oklahoma City. They put the monolayer on this reservoir to study how much it would reduce evaporation, if at all.
“Whenever they were able to keep the lake surface covered, the evaporation reduction was 40 to 60 percent,” says Paul Rodman, who was a graduate student at Oklahoma State University at the time. He went on to work for the U.S. Army Corps of Engineers.
The technique was effective when they could keep the lake surface covered, but that was the problem: the wind kept blowing the monolayer to the shore, exposing the lake surface.
“That was a fatal flaw effectively, as far as discontinuance of that research,” says Rodman. “Eventually, it was dropped and has been dropped now for 45 years or something like that.”
Until Moshe Alamaro and some other scientists picked it back up a few years ago.
He thinks they’ve solved the monolayer’s fatal flaw.
“To make long story short, we place skimmers along the perimeter of the reservoir,” says Alamaro. With his system, when the wind pushes the monolayer to one side, the skimmers suck it up and pump it back to the other side of the reservoir, where it's reapplied.
Of course, Alamaro’s system has only been tested in the lab, not on a large scale.
“It’s not like you can just put this on a pond outside your backyard, because it’s the sheer force of the wind on a large surface of water that’s really the issue that has to be tested. And you can’t do that on a small area,” says UT’s David Maidment. “So, it’s has to be a fairly large area. Not as large as Lake Travis, but fairly large.”
Last year, the Lakeway Municipal Utility District said Alamaro could test his system on a six-acre reservoir they use to store water for irrigation. They applied for permission from the Texas Commission on Environmental Quality last December. The TCEQ says they expected to have everything ready by April 2013. But for Alamaro, things were just taking too long.
In late March, he withdrew the request. He’s looking to test his monolayer system in Massachusetts now.
So, could we ever see monolayers actually being used here in Texas?
The technology would likely cost a fraction of what it would take to build new reservoirs. Both the Texas Water Development Board and the Lower Colorado River Authority, which manages the Highland Lakes, say they’re certainly interested.
But only when – and if – the technology can be proven.