Nader Al-Khateeb, Palestinian general director of Friends of the Earth Middle East, warned that such facilities require a constant supply of power and must be kept running 24 hours a day.
"During the past year, there has been no [reliable] energy in Gaza," Al-Khateeb said. "If they don't have a reliable power supply, they would turn into garbage dumps."
An enormous amount of energy is used to push sourcewater through a membrane that filters out salt. A typical reverse osmosis system, which can also remove some chemicals, takes three to seven kilowatt hours of energy to produce one cubic meter of fresh water, according to a 2008 National Acadamies Press report on desalination.
At that rate, it would take 7,500 kilowatt hours to fill an Olympic-size swimming pool—the same amount of energy the average person in Israel uses over the course of two months, for everything from cooking to driving.
At this point, efficient alternative fuel sources and technology to power desalination facilities are not available.
There is a litany of other environmental considerations and problems—many of them not fully researched—associated with desalination.
High boron concentrations in desalinated water could cause reproductive and developmental toxicity in animals and affect agricultural crops, according to some experts.
While there is concern about desalination of sewage-contaminated seawater, there is a converse problem—overly pure water. The reverse osmosis process used in new facilities can reduce calcium and carbonate concentrations, making the water acidic enough to damage pipes.
Desalination may also remove a range of beneficial ions normally found in drinking water that could have a supplementary dietary role, especially in certain high-risk populations.
Reverse osmosis desalination can discharge chemicals and brine two to three times saltier than seawater back into maritime environments. It is still unclear what the ecological effects of these discharges might be.
"Maybe [desalination] is the only way we can get through the coming years without drawing down aquifers to the point where they're really destroyed," Garb said. "Still, given the energy dimension, the privatization of water supply, and the various minor water-quality issues, I'm a little surprised at how it flew under the radar of the environmental community and of civil society. It's surprisingly understudied given the consequences."
Desalination is also diplomatically problematic, and the Palestinians have historically rejected the idea.
The September 1995 interim Israel-Palestinian peace deal drafted a basis for cooperation on water issues that highlighted the importance of developing new resources, but the Palestinian Authority (PA) rejected an Israeli offer to build them a desalination plant in the Israeli city of Hadera, possibly because Palestinian officials feared agreeing to such a deal would imply a forfeit on their claims to Jordan River water rights. The PA also rejected a separate offer to buy water desalinated in the Israeli port city of Ashkelon.
"When it comes to the West Bank, it is impossible to think about desalination," Al-Khateeb said. "Economically, it is more feasible to take the water [from aquifers] under your feet."
But he would not rule out desalination as an option and said access to drinking water is the bottom line.
"At the end of the day, water is life," he said. "If this is the only alternative and it can help us to avoid future conflicts, we will go for it."
Desalination facilities in Israel are also seen as vulnerable to military or terrorist attacks.
"Seven or eight Hezbollah rockets could knock out our entire water supply. Alongside the geopolitical benefits there are also risks," said Tal. During the 2006 Israel-Lebanon war, Hezbollah fired thousands of rockets at Israel.
One potential method for reducing such risks would be ensuring that water facilities are built and operated jointly by Israelis and Palestinians.
"Desalination Makes Peace Much More Possible"
Hillel Shuval, a veteran expert on the Middle East water conflict at Jerusalem's Hadassah Academic College, sees desalination as providing a window of opportunity.
"Desalination makes peace much more possible for the Israelis," Shuval said. "Because of desalination, I don't think the next Middle East war will be over water," added Tal.
Improvements to the desalination option might include the use of concentrated solar power in place of fossil fuels. But both Israelis and Palestinians at the conference in Amman agreed that desalination and its potential effects are still largely unexplored and should be just part of a diversified long-term response to the water crisis.
They said attention must be turned to restoration of natural watercourses; increasing efficiency of water use and sewage treatment; and reducing local dependence upon water-intensive crops. More effectively using and handling the existing supply of water will actually increase the amount available for human use, they said.
"Trading money for fresh water, it's like magic," Garb said. "But we've got no shortage of examples of silver bullet technologies that seemed like magical ways out of having your back against the wall. And we only started to realize over time what they meant."
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