Global Water Going Fast: How Much Is Left?

New studies reveal that humans are rapidly draining a third of the world's aquifers, and nobody knows how much water is left in them.

The recent reboot of the "Mad Max" movie franchise portrays an apocalyptic future in which civilization has collapsed and leather-clad crazies, who've apparently never heard of alternative energy, are battling over the supply of gasoline. But judging from a pair of just-released scientific studies, the resource that we actually may be fighting over in the future is groundwater.

The new research, led by University of California, Irvine scientists, reveals that humans are rapidly draining water from about a third of the world's biggest underground basins, or aquifers, more rapidly than they can naturally be replenished.

What If California Runs Out of Water?

Worse yet, we don't have a clear idea how much water is left in those natural reservoirs, which in the U.S. alone supply drinking water to about half of the population and are a key source of water for the agricultural irrigation systems that help put food on our tables. That means we may well be in danger of running out, and not even realize it.

"Available physical and chemical measurements are simply insufficient," UCI professor and principal investigator Jay Famiglietti, who is also the senior water scientist at NASA's Jet Propulsion Laboratory, said in a press release. "Given how quickly we are consuming the world's groundwater reserves, we need a coordinated global effort to determine how much is left."

We're already seeing the effects in California, which remains desperately parched due to a brutal extended drought.

Californians have been draining water so rapidly from underground aquifers that tens of thousands of square miles of land reportedly are sinking - so drastically that the shifting surface is starting to destroy bridges and crack highways across the state, according to a recent report by the Center for Investigative Reporting.

The two studies, which are being published in the journal Water Resources Research, represent the first effort to use satellite data to look at groundwater loss all over the planet. The researchers utilized data collect by NASA's twin Gravity Recovery and Climate Experiment satellites. The latter measure dips and bumps in the Earth's gravity which are affected by the weight of groundwater.

Video: Water, Water Everywhere -- 400 Miles Inside Earth

The scientists examined the planet's 37 biggest aquifers over a 10-year period ending in 2013. Of those, eight were overstressed, with no natural replenishment to offset human use. Another five aquifers were extremely or highly stressed, meaning that even though they still had some water flowing into them, it wasn't enough to maintain their water levels.

The most critically endangered water supply in the world was the Arabian Aquifer System, which supplies water to 60 million people in the Middle East. Next on the list was the Indus Basin aquifer of northwestern India and Pakistan, while the Murzuk-Djado Basin in northern Africa was third.

Other institutions that participated in the study included NASA, the National Center for Atmospheric Research, National Taiwan University and the University of California, Santa Barbara.

The withdrawal of groundwater near Lucerne Lake (dry) in San Bernardino County, Calif., has caused the land to subside, leaving fissures on the landscape. Credit: USGS

Ongoing water shortages around the world, along with recent drought conditions in the western United States, have resulted in a flood of new research and proposals around water technology. We take a look at some concepts -- from simple to complex to rather ancient -- that are designed to help us collect, store, transport and even create water where it's needed most.

The severe drought in California -- now in its third year -- has triggered new interest in a relatively old technology. Desalination plants turn seawater into drinking water by way of high pressure valves and semi-permeable membranes. Traditionally an expensive and energy-intensive process, recent innovations have made desalination a more viable option. The city of Carlsbad, Calif., is set to open the biggest

ocean desalination plant

in the Western Hemisphere later this year.

Desalination plants are efficient, relatively speaking, but they're not very pretty. A couple years back, IBM and Airlight Energy turned heads with their

High Concentration PhotoVoltaic Thermal

(HCPVT) system, designed to generate solar power and desalinate water at the same time. The sunflower-shaped solar collectors use a liquid cooling system that could potentially double as a small-scale desalination plant, providing both energy and water for apartment buildings, hotels or hospitals.

Water recycling is the umbrella term for reuse and reclamation systems that involve treating wastewater and returning it to underground aquifers or reservoirs. Along with desalination, it's among the existing technologies being optimized for large-scale use. San Diego's

Pure Water

project, for example, treats wastewater with three different techniques -- membrane filtration, reverse osmosis, and ultraviolet disinfection -- before piping the recycled water back into reservoirs.

One nice thing is that water generating systems tend to scale down nicely. This

Air Orchard

water-harvesting billboard in Lima, Peru, uses dehumidifiers to pull moisture out of the atmosphere. Then a drip irrigation system waters the adjacent garden, producing more than 2.500 heads of lettuce per week. The billboard was built by -- and advertises -- Lima's University of Engineering and Technology.

The Air Orchard is just one of several clever self-advertising projects the university has built to advocate engineering solutions to environmental issues. This

potable water generator

also pulls moisture from the air -- Lima's average humidity is around 80 percent year-round -- and turns it into drinkable water provided by a dispenser at the base.

Lima is the kind of town that doesn't mess around. As the second largest desert city in the world (behind Cairo), it has faced water problems for centuries. A new initiative by the city's water utility plans to

revive ancient stone canals

to bring water down from rivers in the Andes. It's something of a fixer-upper project: The canals were built by pre-Incan civilizations between 500 and 1,000 AD.

The concept of harvesting water with fog nets has been around a long time and some ambitious large-scale projects have been tested across the globe, most notably in


. A few years back, German design student Imke Hoehler proposed a design for portable and collapsible tent-like fog nets that could potentially harvest up to 20 liters of water per day under the right conditions.

Then there are the research projects that get

really, really small.

In March, a team of Japanese scientists proposed studying the microscopic workings of certain moisture-gathering plants to design the next generation of water collection systems. Electron microscope imagery reveals that such plants use cone shaped hairs to catch and store water, then change shape release the moisture in dry conditions. The team hopes advanced fiber technology could essentially replicate the process.

Global droughts and water shortages can seem like terrifying, insurmountable problems. But fear not. As with so many things in this world, William Shatner has our back. The actor and

sci-fi author

recently proposed a plan to pipe water from the Pacific Northwest to arid sections of California by way of -- well, the details are

still fuzzy

. But long-distance water pipelines have a

storied history

in the U.S. and several new projects are in various stages of proposal. And let it never be said that Shatner doesn't follow through: He recently launched the

Shatner Water

website, dedicated to exploring the issue.

Designed and built by the Washington-based engineering firm, Janicki Bioenergy, the very official-sounding Omniprocessor S100 uses heat from sludge to make water. A trial run is underway in Dakar, Senegal, where the machine -- which has received funding from the Bill and Melinda Gates Foundation -- is processing sewage from a community of about 100,000 people. The sewage is first heated intensely to dry it and then during the process, the water vapor is captured, heavily processed and turned into drinking water.