MIAMI: California needs 11 trillion gallons of water to recover from its three-year drought, the US space agency said Tuesday after studying water resources by using satellite data.

The first of its kind calculation of how much groundwater would end the drought was led by Jay Famiglietti of NASA’s Jet Propulsion Laboratory in Pasadena, California and based on observations from Nasa’s Gravity Recovery and Climate Experiment satellites.

California has experienced rainstorms in recent days but, while welcome, scientists warn that they are not enough to end the drought.

“It takes years to get into a drought of this severity, and it will likely take many more big storms, and years, to crawl out of it,” said Famiglietti.

“Spaceborne and airborne measurements of Earth’s changing shape, surface height and gravity field now allow us to measure and analyze key features of droughts better than ever before, including determining precisely when they begin and end and what their magnitude is at any moment in time.

“That’s an incredible advance and something that would be impossible using only ground-based observations.” The more than 40-trillion-liter volume is a huge quantity of water, larger, for example, than the total amount held behind China’s historic Three Gorges Dam.

Published in Dawn, December 17th, 2014