<p>DRY EARTH:</p>

Photo by Roger Lemoyne/Liaison

A woman sits on the ancient steps that once led down to Lake Rajsamand near Udaipur, India. The lake dried up in 2000 due to drainage of its feeder rivers for agricultural purposes and drought.

Eli Raz, an Israeli geologist, found himself in something of a hole, and a rather deep one. He had stopped his car on a desert highway near his home by the Dead Sea to inspect some rock formations. As he was walking a few hundred meters from the road, he felt a rumble and heard a whooshing sound. Then he started falling. When he landed, he found himself at the bottom of a deep sinkhole. The sides were sheer drop-offs and Raz couldn't climb out. Eight hours later, a policeman noticed the hole and found him there. Few, if any, are more qualified to understand such sinkholes: For decades,...


To appreciate the power of politics in water management, one need only return to the hole that swallowed Raz in the Israeli desert in 2003. The Dead Sea is, in a word, disappearing. Normally, the Jordan River feeds this body. In the last few decades, however, Israeli and Jordanian farmers have been siphoning water for agricultural use. That's a worldwide trend: More than 80% of the water used in developing nations goes towards agriculture, according to Lenton.

Today, the Jordan River is little more than a bubbling brook in the north, reduced to a damp mud bed in the south. By the time it reaches the Dead Sea, it is dry. As a result, nary a drop has refilled the Dead Sea, which, because it's located at Earth's lowest point in the middle of a desert and surrounded by reflective cliffs, evaporates rapidly. The sea's shoreline has already retreated some 24 meters in the past 70 years.

As the Dead Sea withdraws, aquifers surrounding it are left at a higher level than its surface. Thus, underground water flows into the sea, drying out aquifers that had been untouched for millions of years. The hollow aquifers become brittle and, occasionally, collapse upon themselves, creating sinkholes that dot the region. Much of the farming done at the Ein Gedi kibbutz has been stopped for fear that laborers will be injured by collapsing sinkholes, according to the Jerusalem Post.

Experts agree that the Dead Sea is in a deep state of crisis. Once thought to be devoid of life, biologists have recently discovered many types of archaea that thrive there. One such species, Halobacterium, has become a new model organism for systems biologists, because it can switch between anaerobic and aerobic conditions based on saline levels, according to the Institute for Systems Biology in Seattle. The Dead Sea is also an important stop for one of the world's largest bird migration routes. If it disappears, it could drastically affect wildlife throughout Europe and Africa.

The World Bank has agreed to spend $400 million (US) to build a pipeline from the Red Sea in the south to the Dead Sea. However, the plan hasn't been set in motion, mainly because of fears that regional violence will sabotage it. Meanwhile, every year, the Dead Sea recedes by another one to two meters.



Courtesy of European Space Agency

This satellite photo shows the massive amount of effluent discharged by the Shanghai region into the ocean. More than 60% of the world's people live in Asia, although the continent has less than a quarter of the globe's fresh water.

There are other ways to obtain water that don't involve technology or construction. In 1994, Allan coined the term "virtual water" to mean the amount of water needed to produce goods. The key is not to import water to thirsty regions, but for those regions to alter their economies so that they export items that need little water during production, and import water-intensive items. Already, some countries have turned the term virtual water into a mantra. Israel, for instance, developed a citrus export industry in the first decades of its existence. Oranges and grapefruits can thrive in the Fertile Crescent's sunshine, but they require a lot of irrigation. So now, the Israeli government stresses high technology exports over citrus, and the industry has dried up. Likewise, Jordan has all but abandoned its emphasis on agriculture and favors other sectors such as tourism and heavy industry.

The prospect of changing virtual water from a descriptive device into global policy is not on anyone's agenda, says Margaret Catley-Carlson, chair of Global Water Partnership, a nongovernmental organization. The world is not ready for international oversight of imports and exports to ensure that virtual water policies are intact, she says. "We're a long way from that, but at least the term virtual water has made many people understand that some of our water policies are unsustainable."

People elsewhere are turning to high technology to solve water problems. One of the more extreme solutions is a huge steel structure blooming in the desert plains of Jalisco, Mexico. At the base of an enormous web of rods and wires (the footprint covers more than an acre) is an electrical ion generator spewing ions into the air. The point of the project, set up by Electrificacion Local de la Atmosfera Terrestre (ELAT), is to cause rain to fall.

The results appear promising, but studies to date lack scientific rigor. Ionogenics, a Boston-based company that licenses ELAT's technology in the United States, claims that over the last three years, 17 generators located throughout six Mexican states caused rainfall to increase by 50% and bean production by more than 60% in the country's central basin region. Of course, correlation is difficult to prove, especially when accurate rainfall statistics for that region have never before been available. In addition, traditional cloud-seeding technologies also have been short on statistical evidence of efficacy. In optimal conditions, seeding clouds with expensive, harsh chemicals such as silver iodide can increase rainfall by 15% at most.

But many are convinced that the plan is working, and Ionogenics is now negotiating for a pilot project in Texas. "We're confident that, if given the chance, we can produce the kinds of results that will satisfy the scientific community that this technology not only works, but works exactly like we say it does," says Judy Lazaro, Ionogenics' vice president of business development. Not all atmospheric scientists share her enthusiasm. "It does not have any physical basis that I can see," says William R. Cotton, a professor of atmospheric sciences at Colorado State University.



The Holy Grail of water technologists, however, is not producing more rain but using the biggest ponds of all, the oceans. If an affordable way could be found to squeeze the salt out of seawater, the accessibility problem would be officially over. Eighty percent of the world's population lives within 200 kilometers of a coastline.

Desalinating seawater is a costly endeavor, mainly because it craves energy. More than 11,000 desalination plants, cleaning billions of liters of water a day, are located throughout the world, primarily in the Persian Gulf. Most of those Gulf-based plants use an older technology called multistage flash distillation, which basically boils the water. The process is extremely energy-intensive, which presents a problem for just about every country except those in the oil-rich Gulf countries.

Reverse osmosis (RO), a more economical technology, uses filters with microscopic pores to strain salt out of water. Thanks to new membrane technologies (which have reduced the cost of such membranes by 80%), RO has become cheaper than flash distillation in the last decade, according to Stamford, Conn.-based Poseidon Resources. However, a great deal of energy is still required to create the pressure needed to push potable water out of the filters. According to the Texas Water Development Board, 1,000 US gallons (equivalent to 3,785 liters) of RO-desalinated seawater costs $2.50, more than double the average price of naturally occurring, fresh water sources. Several large RO plants are being built in the developed world, including Tampa, San Diego, and Singapore. Because most of that price is still linked to energy expenditure, there's little hope that RO will be a primary source of fresh water for the world's poor populations in the future.

Over the last few years, however, a new technology has appeared that provides some hope that desalination might eventually become much cheaper. Developed at the Lawrence Livermore National Laboratory in 1995, capacitative deionization (CD) uses a new substance called carbon aerogel to extract the salt. Aerogel is an extremely porous solid substance consisting of 98% air. Water flows over an aerogel cell that is charged with a 1.2-volt electrical current. As the water moves over the aerogel's surface, salt ions are attracted to the charged cell, affixing themselves inside its pores. Once the aerogel is filled with salt, the polarity is reversed and the salt is flushed.

The CD technology has since been leased to a private company, CDT Systems in Dallas. CDT is trying to create a workable mobile system that can be sold to defense contractors or mining operations. The cost of the original aerogel cell at Laurence Livermore was nearly $75,000, but CDT president Dallas Talley claims his company can reduce that figure to $2,000. "And we're still very low on the learning curve on how to manufacture these things cheaply," he says. His company is arranging financing for a new factory to produce large volumes of aerogel cells.

Even at $2,000 for a cell that produces 3,785 liters of desalinated water per day, the cost still exceeds that of reverse osmosis. The reason for excitement about his company's system, says Talley, is that if the capital costs of producing aerogels do come down, then the system becomes very attractive, because energy use is negligible. "The amount of energy we need to desalinate 1,000 gallons of water a day is equivalent to running a 100-watt light bulb."

The ocean's inhabitants would not be harmed by these desalination efforts, researchers say. The larger, and more environmentally dangerous issue, is where to put all that extracted salt. Various plans include diluting it and shipping it to waste sites.


<p>THEN AND NOW:</p>

Courtesy of UNESCO/Dominique Roger

Modern Iraqi farmers, like these near the city of Kut, use irrigation methods similar to those practiced by their ancestors. Today, irrigation accounts for nearly 80% of the world's water consumption.

Development strategists are wary of investing in such expensive technologies in the hope that they eventually will become cost-effective. Some of the more utilitarian water technology research is being done on creating systems that are simple and super-cheap. That's why Wilderer spends his time in his Munich lab monitoring a model sewage system that automatically recycles household water multiple times; the point is that whatever is used returns to the house after it's cleaned. "The cheapest water in the regions that are hardest hit by the water crisis is the water that's already been used," says Wilderer.

His system involves up to six sets of plumbing pipes, as opposed to the two traditional input and output lines. Water used in the kitchen returns to a neighborhood bioreactor, which filters the water and ferments the kitchen waste to produce methane gas, which is used for energy. Water used in the shower and washing machine goes back to the neighborhood processing center to filter out detergents, a relatively cheap processing method, which also produces industrial chemicals as a byproduct; these can be sold to help pay for the system.

The system has a specially designed toilet that separates body waste into two separate discharge flows. The solid waste is sent through the main sewer to a municipal treatment plant where it composts into fertilizer. The urine is separately processed to produce valuable ammonia fertilizer. "The separation of toilet waste is the key to making this system affordable," Wilderer says. That's because more than 60% of the cost of municipal waste treatment goes towards nitrification and denitrification, chemical processes that essentially remove the urine from solid waste by brute force. By recycling the waste at the source and then separately treating the two waste streams, Wilderer says that his system automatically cuts treatment costs in half.

Nevertheless, the system still has a flaw or two, and even if perfected, it can be installed only in new construction. Imagine the costs of ripping the walls out of an apartment building to create room for six sets of pipes.

Some human behavior must be altered in the process, too. Wilderer has designed a test toilet that activates when someone sits on the seat, but he discovered that female subjects produced drastically less urine than males. After trying to fix the seat in the women's bathroom and obtaining the same results, he finally polled the testers and found that about half the women hover over the toilet seat, avoiding direct contact for hygiene reasons. "I didn't know that because I had never been inside a women's bathroom before," says Wilderer. "And it's not the kind of habit people talk about at dinner parties."

Sam Jaffe can be reached at sjaffe@the-scientist.com.

Adding Salt To A Staple's Diet

<p>ALL WET:</p>

Courtesy of Kenneth A. Rahn

About half of the world's population subsists on rice, one of the most water-intensive crops. If saltwater could be used for flooding paddies, it would reduce the water burden on some areas where shortages are most critical.

No crop requires more water than rice. One kilogram of this staple requires 1,500 liters of water, according to the United Nations' World Water Development Report. The water, often drawn from rivers, becomes salty because of high evaporation rates, which then salinizes surrounding bodies of water. To top it off, microbes in the rice paddies generate more methane than any other source (100 million metric tons a year), according to Greenhouse Gas Online. This lethal gas withholds four times more heat than carbon dioxide.

Asking people to give up rice is one way to reduce the world's water crisis, but half the world's population consumes it. A more clever and less politically risky solution would be to adapt rice to tolerate saltwater while producing the same yield. Many rice strains currently can grow in brackish water (about half the salt level of seawater), but they produce very little usable seeds.

In as-yet unpublished research, Fred Van Eeuwijk and graduate student Baboucarr Manneh of Wageningen University, Netherlands, genetically screened more than 100 rice cultivars; they found quantitative trait loci, or biomarkers, that always are present in the rice with high-salt tolerance. "We don't know what those genetic regions do yet, but that's the next step," says Van Eeuwijk.

Many salt-tolerance pathways are already understood, especially those in the root system, which increase the salt levels in root cells while the rest of the plant maintains healthy salt levels. However, little is known about the timing of those pathways, says plant geneticist Hans Bohnert, University of Illinois at Urbana-Champaign. He looked at several rice cultivars, including some known for salt tolerance and others that are extremely salt-sensitive.1

"We found that they have the same toolbox to deal with the presence of salty water, but the difference is the rapid reaction of the salt-tolerant cultivars," says Bohnert. Whereas the salt-sensitive plants, when placed in salty water, took 24 hours to activate their stress-response mechanism, the salt-tolerant plants did so in a matter of minutes. Now Bohnert plans to breed the two; he hopes that a new hybrid will be salt-tolerant and achieve the high yields of the salt-sensitive cultivars.

- Sam Jaffe

"Salinity stress-tolerant and -sensitive rice (Oryza sativa L.) regulate AKT1-type potassium channel transcripts differently," Golldack D, Plant Mol Biol , 2003 Vol 51, 71-81

Interested in reading more?

Become a Member of

Receive full access to digital editions of The Scientist, as well as TS Digest, feature stories, more than 35 years of archives, and much more!
Already a member?