Some of the world’s most important farming regions rely on freshwater from large underground aquifers that have filled up slowly over thousands of years. Think of the Central Valley aquifer system in California. Or the Indus basin in Pakistan and India. This groundwater is particularly valuable when rain is scarce or during droughts.
But that groundwater may not last forever. Data from NASA’s Grace satellites suggests that 13 of the world’s 37 biggest aquifers are being seriously depleted by irrigation and other uses much faster than they can be recharged by rain or runoff. And, disturbingly, we don’t even know how much water is left in these basins. That’s according to a 2015 paper in Water Resources Research.
The map below gives an overview. There were 21 major groundwater basins — in red, orange, and yellow — that lost water faster than they could be recharged between 2003 and 2013. The 16 major aquifers in blue, by contrast, gained water during that period. Click to enlarge:
The researchers found that 13 basins around the world — fully one-third of the total — appeared to be in serious trouble.
Eight aquifer systems could be categorized as “overstressed”: that is, there’s hardly any natural recharge to offset the water being consumed. In the direst state was the Arabian aquifer system beneath Saudi Arabia and Yemen, which provides water for 60 million people and is being depleted by irrigation for agriculture. Also in bad shape were the Indus Basin that straddles India and Pakistan and the Murzuq-Djado Basin in Africa.
Another five aquifer systems were categorized as “extremely” or “highly” stressed — they’re being replenished by some rainwater, but not nearly enough to offset withdrawals. That list includes the aquifers underneath California’s Central Valley. During California’s recent brutal, five-year drought, many farmers compensated for the lack of surface water by pumping groundwater at increasing rates. (There are few regulations around this, though California’s legislature recently passed laws that will gradually regulate groundwater withdrawals.)
The result? The basins beneath the Central Valley are being depleted, and the ground is actually sinking, which in turn means these aquifers will be able to store less water in the future. Farmers are losing a crucial buffer against both this drought, if it persists, and future droughts.
The big question: How soon until these aquifers run dry?
Here’s the other troubling bit: It’s unclear exactly when some of these stressed aquifers might be completely depleted — no one knows for sure how much water they actually contain.
In a companion paper in Water Resources Research, the researchers took stock of how little we know about these basins. In the highly stressed Northwest Sahara Aquifer System, for instance, estimates of when the system will be fully drained run anywhere from 10 years to 21,000 years. In order to get better measurements, researchers would have to drill down through many rock layers to measure how much water is there — a difficult task, but not impossible.
“We don’t actually know how much is stored in each of these aquifers. Estimates of remaining storage might vary from decades to millennia,” said Alexandra Richey, a graduate student at UC Irvine and lead author on both papers, in a press release. “In a water-scarce society, we can no longer tolerate this level of uncertainty, especially since groundwater is disappearing so rapidly.”
The researchers note that we should figure this out if we want to manage these aquifers properly — and make sure they last for many years to come. Hundreds of millions of people now rely on aquifers that are rapidly being depleted. And once they’re gone, they can’t easily be refilled.
— Saudi Arabia squandered its groundwater and agriculture collapsed. The rest of the world should take note.
2050: A Space Odyssey
A Japanese company, called Obayashi Corporation, recently announced that it intends to build a fully working space elevator by the year 2050. This space elevator would drastically reduce the risks and costs associated with space travel in the future. A space elevator would act as a direct transport route to the frontier of space.
The space elevator still has a lot of theoretical challenges to overcome before it can be realised. Currently the largest challenge facing the space elevator project is the creation of a cable that would be strong enough to support the immense forces that it would be subjected to.
Advances in research into nanotechnology and carbon nanotube materials are now presenting us with the opportunity to create a cable that could actually handle the forces that would be exerted on it.
Researchers are currently exploring the idea of using ‘diamond nano-threads’ as the material of choice for a space elevator cable. These nanothreads, which are currently being developed by John V. Badding and his research team at Penn State University, have a unique structure compared to other carbon nanotubes.
John Badding, Professor of Chemistry at Penn State, Talks About his Research
The unique structure which diamond nanothreads have is achieved by compressing benzene, a ring of six carbon atoms, causing the benzene to stack. Eventually the pressure becomes too much and the benzene breaks apart, only to reform again in the shape of a tetrahedron as the pressure is slowly released by the scientists.
One of our wildest dreams for the nanomaterials we are developing is that they could be used to make the super-strong, lightweight cables that would make possible the construction of a space elevator which so far has existed only as a science-fiction idea.
John V. Badding, Professor of Chemistry at Penn State University
Badding’s team are the first to develop a structure in which tetrahedrons, pyramids with a triangular base, are connected end by end in order to form an incredibly strong structure.
Creating Incredibly Light and Incredibly Strong Cables
The strength of a diamond nanothread means that this nanomaterial could be used to create the cables of a space elevator. The cables need to be both incredibly light and incredibly strong in order to provide the stability required for a space elevator to operate.
Diamond nanothreads would be ideal for this use due to their stiffness and strength, as well as the fact that they are light in weight. However, currently used processes and techniques to create carbon nanotubes have limitations and are not yet able to produce the quantity or quality of nanomaterials which a space elevator cable would require.
However, the Obayashi Corporation believes that large scale production technology will have been established by 2030, leading them to predict that they could complete their space elevator project by 2050. The construction of a cable is the first step in creating a space elevator because it requires the most research in order to be fully realised.
Diamond Nanothreads – Image Credit: John Badding Lab | Penn State University
The Main Components of a Space Elevator
The other four main components required to build a space elevator are:
- an anchoring station placed on the surface of the earth
- a counterweight in space which will help stabilise the orbit of the cable
- a mechanical lifter to pull the elevator up the cable
- a power source located on the earth to deliver power to the elevator
The Anchoring Station
The anchoring station will serve as a starting base for space elevator missions and will most likely originate from a location in the Pacific Ocean. Using a location on the surface of the Pacific Ocean would allow the anchoring station to move along the ocean surface to help the cable avoid any threatening objects. A location along the equator in the Pacific Ocean would also help to minimise the threat that extreme weather could pose to the space elevator and its operation.
The counterweight helps to stabilise the space elevator by keeping the cable at its maximum length and tension as it orbits around the earth. Researchers believe that the ideal counterweight could be the same spacecraft which will be used to launch the cable into space. This dual purpose spacecraft/counterweight would help to minimise the economic costs of the counterweight and the spacecraft delivering the cable.
An Elevator to Space: Markus Landgraf at TEDxRheinMain
The Mechanical Lifter
The mechanical lifter will work in conjunction with the cable to provide the elevator with its vertical motion. One of the potential designs for the lifter is a series of rollers with traction tread that would look something similar to the rollers on a tank. These rollers would pull the cable through the space elevator and thus pull the elevator upwards into space.
The Power Source
The power source will wirelessly deliver power from the anchoring station to the space elevator as it makes its journey upwards towards space. This can be done by firing a laser at photovoltaic cells, which will convert the energy from the laser into electricity that the mechanical lifter can use.
Whilst the concept of wirelessly transferred power sounds like something straight from the pages of a science fiction novel, we have been using microwaves to fly model aircraft for over 20 years.
Some Challenges to Overcome
Even if all of these components work in unison there are still a number of challenges that need to be overcome in order to create a working space elevator. For example, low earth orbit objects could potentially damage or cut the cable that the space elevator is using. If the cable was to be cut it could fall back to the earth and cause enormous damage to the anchor station and the surrounding area.
Another major concern which has to be considered is the political impact of creating a space elevator. If the space elevator’s anchor station is situated in international waters, then who would own the space elevator and how would you equally share the usage of the space elevator? These are just a few of the issues which have to be resolved before the space elevator becomes a reality.
Why is it Worth the Effort?
The current cost of transporting cargo into space using spacecraft is around $20,000 per kilogram. Using a space elevator, Obayashi claims that this cost will be drastically reduced to just of only a few hundred dollars per kilogram of cargo. Apart from the obvious benefits of transporting material into space in a more cost effective manner, a space elevator also has huge applications for space launches.
Overcoming the Earth’s gravitational field and atmosphere is one of the major costs and difficulties associated with a space shuttle launch. However, if a space elevator could transport a spacecraft into space ready to be launched, then the effects of gravity and atmosphere would no longer pose a challenge to space travel in the future.
The development of a space elevator represents an important first step towards travel and exploration into deep space, as well as opening up the possibility of a civilisation that spans our solar system.
References and Further Reading
|NASA has selected UT Arlington as one of four U.S. institutions to develop improved methods for oxygen recovery and reuse aboard human spacecraft, a technology the agency says is crucial to “enable our human journey to Mars and beyond.”|
|NASA’s Game Changing Development Program awarded $513,356 recently to the UT Arlington team. UT Arlington and three other teams are charged with the goal of increasing oxygen recovery to 75 percent or more.|
|Principal investigators on the UT Arlington project are Brian Dennis, associate professor of mechanical and aerospace engineering in the College of Engineering; Krishnan Rajeshwar, distinguished professor of chemistry and biochemistry in the College of Science; and Norma Tacconi, a research associate professor of chemistry and biochemistry.|
|Principal investigators on the UT Arlington project are from left: Krishnan Rajeshwar, distinguished professor of chemistry and biochemistry in the College of Science; Brian Dennis, associate professor of mechanical and aerospace engineering in the College of Engineering; and Norma Tacconi, a research associate professor of chemistry and biochemistry.|
|They will design, build and demonstrate a “microfluidic electrochemical reactor” to recover oxygen from carbon dioxide that is extracted from cabin air. The prototype will be built over the next year at the Center for Renewable Energy Science and Technology, CREST, at UT Arlington.|
|“At the end of this 15 month Phase I project, we will demonstrate the prototype to NASA officials. If we are selected to move to Phase II, we plan to build a full-scale unit. We hope the technology will be flight tested on the International Space Station sometime in the future,” Dennis said. “That’s what we’re really excited about and what we’ll be aiming for.”|
|Dennis said the design uses water and carbon dioxide as reactants and produces oxygen and hydrocarbon gases, such as methane. The gases can be vented into space and the oxygen is used for breathing.|
|“We have developed a nanocomposite electrode that speeds oxygen evolution at lower potential. That basically means it can produce more oxygen in a shorter time with less power and less reactor volume,” said Dennis. “This is important since power on a spacecraft is limited because it comes from solar panels and spacecraft capacity also is limited. Things should be as compact and lightweight as possible.”|
|Current methods of oxygen recovery used on the International Space Station, or ISS, achieve only about a 50 percent recovery rate. A better recovery rate means less oxygen needs to be stored and would free up precious cargo space on prolonged missions. With current technology, a trip to Mars would take about eight months, though scientists are working to shorten that time.|
|In a statement from NASA, Associate Administrator for Space Technology Michael Gazarak said improving oxygen recovery and designing a system with high reliability is crucial to long-duration human spaceflight.|
|“These ambitious projects will enable the critical life support systems needed for us to venture further into space and explore the high frontier and are another example of how technology drives exploration,” Gazarak said. NASA’s full announcement is available here.|
|Dennis said the proposed UT Arlington device has an advantage over the ISS method because not as much water is needed to achieve 75 percent recovery. The team estimates its system would require less water than what can be recovered in one day from a person’s sweat and urine. A water recovery system that converts bodily fluids to water is already at work on the ISS.|
|For years, Dennis, Rajeshwar and Tacconi have developed novel nanocomposites to be used in targeted electrochemical reactions for fuel cells and other purposes. The new project builds on that work and is another demonstration of the key role electrochemistry can play in technological advances, Tacconi and Rajeshwar said.|
|James Grover, interim dean of the UT Arlington College of Science, said the new NASA-funded project is a great chance for the College of Science and College of Engineering to make an impact in a field that captures human imagination and inspires innovation.|
|“Discoveries are cultivated through interdisciplinary collaboration and UT Arlington scientists and engineers have embraced that spirit to achieve advances,” Grover said.|
|Khosrow Behbehani, dean of the College of Engineering, said the interdisciplinary project speaks to practical aspects of space research.|
|“This project has great implication for space explorations,” Behbehani said. “Through collaboration of scientists and engineers at UT Arlington such innovations have become possible which can put us closer to exploring farther destinations in space.”|
|Source: University of Texas at Arlington|