Nov. 8, 2007 -- Dreams of someday watering crops with desalinated water have hit a small snag.
Farmers using drinking-quality water from the world's largest desalination plant in Ashkelon, on Israel's southern Mediterranean coast, have discovered that the water is lacking in some needed elements, like calcium and magnesium, and too rich in boron.
That's not a problem for humans drinking the water, but it's terrible for tomatoes, basil, citrus trees, flowers and other economically important plants. Fortunately, with some adjustments and fertilizers, the water can be made usable for farmers, now that the problem is recognized.
"The conventional wisdom was that desalination is an incredible bonus for farmers," said Alon Tal, of Ben-Gurion University's Negev Sede Boger Campus in Israel.
Read Larry O'Hanlon's blog: Earth Impacts
The bonus would be that desalinated water helps reduce the salts in soils. In theory the excess salts found in the soils of many hot, dry parts of the world could be made less salty with desalinated water. And since few food plants are especially salt tolerant, that would be a bonus for growers fighting salty ground.
The newfound drawbacks of desalinated water only came to light because until recently desalinated water was too expensive to use on crops. It's the scale and high efficiency of the Ashkelon plant, however, that lowered the cost of the water to where it became attractive to Israeli farmers.
"The desalinated water was not planned or anticipated to ever be supplied to farmers for irrigation -- it was always promoted as being for domestic/municipal consumption," explained Alon Ben-Gal and Uri Yermiyahu, who are coauthors with Tal on a paper about the findings in the Nov. 9 issue of the journal Science.
"Only after production began did we discover that much of the water was actually being channeled to agricultural areas."
But, as the team reports in their paper, 69 percent of the global water supply goes toward irrigation. So by dropping the price of desalinated water in places where high-value cash crops are being grown, watering those thirsty plants becomes economically feasible.
In Spain almost a quarter of desalinated water is used for irrigation and an Australian survey found that more than half of the people in that country could envision the use of desalinated water for growing vegetables, the team reports.
In the United States desalinated water hasn't yet made it into agricultural use, says Andrew Chang, director of the Center for Water Resources at the University of California in Riverside.
But that's not to say it won't someday. As in Israel, it's all a matter of economics.
The municipal desalination plant in Santa Barbara, California, for instance, was built to stave off droughts. But has never been needed since it costs more to produce desalinated water than to import water from other parts of the state, Chang told Discovery News.
Still, as water becomes scarcer, those prices will change and the Israeli experience could become common.
Related Links:
Santa Barbara County Public Works: Desalination
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