Seventy-six years after the invention of the modern sprinkler helped revolutionize farming, lasers may revolutionize it again.
Jan Kleissl and a handful of his students at the University of California at San Diego think technology using laser beams might lead to a better way to conserve the millions of gallons of water sprayed each year on thirsty crops.
He and his team are using a large aperture scintillometer to study how much water crops lose to evaporation and the peak times that water disappears.
The hope is to give farmers a more accurate, up-to-date reading of how efficiently their crops are using water than current technology allows.
"What's new about our approach is the monitoring side of it," Kleissl said by phone from his office. "We're trying to improve on that."
Some advancements in irrigation have focused on water delivery system – such as sprinklers. But while most farmers are experts at managing their irrigation by sight, recent years' droughts have called for more sophisticated ways to use – and save – water.
Water became an even more valuable commodity in California last year, when a federal judge ordered federal and state agencies to restrict pumping in the Sacramento-San Joaquin River Delta to protect the threatened delta smelt, severely cutting the growers' supply.
Further restrictions could result from last month's decision by state fish and wildlife managers to limit pumping to protect another native fish, the longfin smelt.
These shortages are prompting researchers to devise new ways to determine when to irrigate and how much water to use, said Khaled Bali, an irrigation expert for the University of California Cooperative Extension.
"There's not enough water to go around," he said.
San Diego County farmer Bob Polito, who was forced to remove 10 of his 60 acres of citrus and avocado trees from production after last year's pumping restrictions, said high-tech irrigation aids have so far been too expensive. But he said the increasing scarcity of water may force him to invest in technology to monitor his trees' water efficiency.
"Anything that gives you an accurate accounting on that score would be a help to farmers," Polito said.
Researchers also are testing a device that measures the velocity at which sap creeps up trees. When the sap's movement slows, growers would know that the trees need less water and reduce the amount that they use.
Other tests involve using satellite imagery to measure "evapotranspiration" – the amount of water that seeps into the atmosphere from soil surfaces and plants. During periods of slow evapotranspiration – when plants require less water – farmers can cut down on irrigation.
Many farmers already use a formula based on historic evapotranspiration averages gleaned from meteorological data – combined with on-site observations – to devise their irrigation strategies.
But Kleissl's team hopes to give farmers more valuable information by using the scintillometer, which focuses laser beams across a farm field and records fluctuations of the refractive index of air that is caused by such things as changes in temperature and humidity.