THE discovery of several salty springs beneath the Sea of Galilee may
eventually lead to an improvement of water supplies in Israel. By capping the
springs, scientists hope to decrease the sea鈥檚 salinity, which may guarantee
Israel鈥檚 supplies of fresh water.
The Sea of Galilee, also known as Lake Kinneret, is fed by the River Jordan,
which carries very little salt. 鈥淚t comes into the lake carrying 20 milligrams
of chloride per litre,鈥� says Michael Krom, a geochemist at the University of
Leeds. But water also enters the sea from springs, some of which are highly
saline.
Two decades ago, overground springs on the western shore were diverted away
from the lake, helping to reduce the level of chloride ions from 385 to 240
milligrams per litre. But this is still much too salty to drink. Water from the
lake provides 30 per cent of Israel鈥檚 needs, but must be diluted with purer
water before being added to the national supply. The water is also used to
irrigate crops in the Negev desert, where the salt collects in the soil.
Flushing away this salty crust costs Israel millions of gallons of precious
clean water each year.
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Krom and his Leeds colleague Robert Mortimer, working with Ami Nisri of the
Lake Kinneret Research Laboratory and Mira Stiller of the Weizmann Institute of
Science in Rehovot, believe they have now discovered why the Sea of Galilee
remains so salty.
鈥淎ll of the mud at the bottom of the lake has salt oozing out through it,鈥�
says Krom. 鈥淚n a number of places, springs punch through it. We鈥檝e found three
so far, one of which is very strong.鈥�
To detect the springs, the researchers dropped a probe containing
polyacrylamide gel into the mud on the lake bed, where it absorbed ions. Back at
the surface, the gel was sliced very thinly, and each slice was placed in fresh
water to release its ions. This gave an accurate measurement of the ion
concentration at different levels in the mud. 鈥淥ne sample went from 250
milligrams of chloride per litre on the bed of the lake to 10 000 milligrams per
litre just 10 centimetres down in the mud,鈥� says Krom.
The researchers say that local fisherman could have served as good guides to
the location of the salty springs. 鈥淔or some reason, fish like to gather around
them,鈥� says Nisri. 鈥淚t鈥檚 probably that they prefer the slightly higher
temperature of the water, rather than liking the more saline environment.鈥�
Krom and his colleagues are now working out which springs to cap to achieve
the most rapid reduction in the sea鈥檚 salinity. 鈥淚n practice we can鈥檛 stop all
the springs,鈥� he says. But Israel鈥檚 Water Commission has set a target of
reducing the lake鈥檚 salinity to below 150 milligrams per litre.
Exactly how the springs might be capped has not yet been worked out, so the
researchers cannot say whether the commission鈥檚 target is attainable.
