Reporter 395, 20 January 1997

Earth Sciences duo find the salt in the Sea of Galilee

The Sea of Galilee has been known through history as the site where, according to the Bible, Jesus calmed the waves to walk on water. For centuries it has had other mysteries too. This inland lake in Israel is very salty, much too salty to drink. The source of this salinity has long puzzled scientists as the Sea is fed by the River Jordan, which carries very little salt.

Israel relies on the Sea for thirty per cent of its water, so high salt levels - 240 milligrams per litre - pose quite a problem. Water from the Sea must be diluted with pure water before going into the water supply. Salt deposits also have to be flushed away from agricultural land in the Negev desert. Such measures cost Israel millions of pounds and the loss of much precious clean water each year.

Now the mysteries of this saline lake have been revealed by Dr Michael Krom and Dr Robert Mortimer, from the University's Earth Sciences department. They have identified underground salt springs flowing directly into the bottom of the lake and, by diffusion, through the mud.

"All of the mud at the bottom of the lake has salt oozing through it," says geochemist Michael Krom, who has just returned from a field trip to the Sea of Galilee. "In a number of places, springs punch through it. We've found three so far, one of which is very strong."

Krom and Mortimer developed an innovative probe containing polyacrylmide gel to produce exact measurements of chlorinity and other salts at different levels in the mud. Divers inserted gel probes into the lake bottom and extracted sediment cores for sampling. On the lake bed, the gel absorbed ions. Back on the surface, the Leeds scientists soaked thin slices of the gel probe in fresh water to release the ions. "One sample went from 250 milligrams per litre on the bed of the lake to 10,000 milligrammes per litre just 10 centimetres down in the mud," says Dr Krom.

Krom and Mortimer have joined a team of Israeli scientists, including Dr Ami Nisri from the Lake Kinneret Research laboratory and Dr Mira Stiller from the Weizmann Institute, Rehovot, on a project sponsored by the Israeli Water Commission. The aim is to reduce the lake’s salinity to below 150 milligrams per litre. The challenge now is to determine exactly how much of the salt emerges through the mud and how much enters the Sea of Galilee through distinct underwater springs. The team will then use this information to cap some of the larger springs and to divert salty water away from the lake. Israel's supplies of fresh water may at last be guaranteed.

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