person:james famiglietti

Earth’s Disappearing Groundwater
▻http://earthobservatory.nasa.gov/blogs/earthmatters/2014/11/05/earths-disapearing-groundwater

http://earthobservatory.nasa.gov/blogs/earthmatters/files/2014/11/nclimate2425-f2.jpg

Earth is home to yet another type of water—groundwater—which includes all the fresh water stored underground in soil and porous rock aquifers. Though groundwater is often forgotten because it’s not visible, more than two billion people rely on it as their primary water source.

With drought afflicting several parts of the world, and with aggressive use of groundwater in many agricultural regions, this precious water resource is under serious strain, warns NASA Jet Propulsion Laboratory hydrologist James Famiglietti.

(...)

The first step to managing the globe’s groundwater problem is to accept that we have one, Famiglietti recommends. And when societies are ready to look for solutions, the first place they’ll have to turn is the agricultural sector. “#Agriculture accounts for nearly 80 percent of water use globally, and at least half of the irrigation water used is groundwater,” he wrote. “Even modest gains in agricultural efficiency will result in tremendous volumes of groundwater saved, or of water available for the environment or other human uses such as municipalities, energy production, industry and economic growth.”

#eau #nappe_phréatique #sècheresse #climat

#NASA Bombshell: Global Groundwater Crisis Threatens Our Food Supplies And Our Security | ThinkProgress
▻http://thinkprogress.org/climate/2014/10/31/3586561/global-groundwater-crisis

An alarming satellite-based analysis from NASA finds that the world is depleting groundwater — the water stored unground in soil and aquifers — at an unprecedented rate.

A new Nature Climate Change piece, “The global groundwater crisis,” by James Famiglietti, a leading hydrologist at the NASA Jet Propulsion Laboratory, warns that “most of the major aquifers in the world’s arid and semi-arid zones, that is, in the dry parts of the world that rely most heavily on groundwater, are experiencing rapid rates of groundwater depletion.”

The groundwater at some of the world’s largest aquifers — in the U.S. High Plains, California’s Central Valley, China, India, and elsewhere — is being pumped out “at far greater rates than it can be naturally replenished.”

The most worrisome fact: “nearly all of these underlie the word’s great agricultural regions and are primarily responsible for their high productivity.”

And this is doubly concerning in our age of unrestricted carbon pollution because it is precisely these semiarid regions that are projected to see drops in precipitation and/or soil moisture, which will sharply boost the chances of civilization-threatening megadroughts and Dust-Bowlification.

As these increasingly drought-prone global bread-baskets lose their easily accessible ground-water too, we end up with a death spiral: “Moreover, because the natural human response to drought is to pump more groundwater continued groundwater depletion will very likely accelerate mid-latitude drying, a problem that will be exacerbated by significant population growth in the same regions.”

So this is very much a crisis, albeit an under-reported one. But why is NASA the one sounding the alarm? How has the space agency been able to study what happens underground? The answer is that NASA’s Gravity Recovery and Climate Experiment (GRACE) satellite mission can track the earth’s mass over space and time — and large changes in the amount of water stored underground cause an observable change in mass.

#eau #agriculture