WASHINGTON. — Washington.--It has brought Syria, Iraq and Turkey to the brink of armed conflict. Historians have found it in the roots of Israel's six-day war with the Arabs. Jordan's King Hussein said last July that it alone could drive him back to war. And Iraqi President Saddam Hussein tried unsuccessfully to use it as a weapon in the Persian Gulf war.
The focus, for once, is not on oil or boundary lines or political rights or tribal rivalry or religious persecution, but on one of the most fundamental of human needs -- water.
And in Israel, for instance, where much of the country's underground water supplies lie beneath the Arab West Bank, experts say the question of water rights could be crucial to a political solution of the Palestinian question.
Among the Middle East's scarcest assets, water -- the competition for it and fierce protection of access to it -- has been a source of tension and conflict between peoples and nations of this politically divided region since Biblical times.
The greatest battle, however, still lies ahead, experts say. They warn that the region is running out of cheap, uncontaminated water supplies. As competition for the resource mounts, both within and between nations, further conflicts are bound to arise; unless the countries can adopt a new -- some think unlikely -- spirit of tolerance and co-operation.
"The water crisis has arrived, and it's four years earlier than we thought," said Joyce Starr, a specialist in Near Eastern affairs and head of the Global Water Summit Initiative, a non-profit research group that focuses attention on international water security issues.
Water experts, she said, had predicted that virtually the whole Middle East south of Turkey, with the exception of water-sufficient Lebanon, would face "a dire water crisis" by 1995. The last two-to-three years of drought, however, had hastened the inevitable, she said, and turned prediction into reality this year.
"Jordan, Israel, Yemen and the Arabian peninisula are already extracting ground water in excess of recharge. In other words they are already mining this precious resource," said Willi Wapenhans, vice president for European, Middle Eastern and North African agricultural projects at the World Bank.
The situation is being aggravated by the explosion in Middle Eastern population which, Mr. Wapenhans said, is growing by more than 3 percent a year -- one of the highest rates in the world -- and could place another 100 million people in the desert region and North Africa by the end of the century.
Jordan's population is growing at around 3.8 percent which, demographers say, is the highest in the region, while the huge influx of Soviet immigrants to Israel adds a further element of tension to one of the driest and most politically unstable areas of the Middle East.
The growth is concentrated mainly in urban areas, Mr. Wapenhans said, which means that the costs of future water developments will probably skyrocket, because city water, which has to be pure enough to drink, costs far more to produce than less-pure water for irrigation of crops. Currently most Middle Eastern water -- fully three-quarters of current provision, he said -- is suitable only for agriculture.
So vast and harsh are the Arabian deserts that Saudi Arabia and Kuwait have had to desalt seawater to provide for nearly all of their fresh water and industrial needs. In fact, Dr Starr said the Persian Gulf states account for 60 percent of the world's desalination processing, half of that 60 percent in Saudi Arabia alone.
But only the wealthy few can afford such expensive processes. The World Bank points out that the Middle East already #i produces the most expensive water in the world, costing around $300 a person in 1985 -- about twice what it costs in North `D America.
Heavy dependence on desalination can also leave a country strategically vulnerable in time of war. During its occupation of Kuwait, Iraq destroyed all of that country's desalination plants, and in the consequent war, almost succeeded in clogging the inlet pipes of Saudi Arabia's largest desalting plant with a huge oil slick that it caused to drift down the Persian Gulf.
Iraq itself is one of the most fertile of the Arab countries, encompassing the Tigris and Euphrates delta, home of Mesopotamia, one of the ancient world's first agricultural successes. But the demands and practices of modern agriculture -- not to speak of modern warfare -- have exhausted much of the resources of present-day Mesopotamia. Agronomists say only one-third of Iraq is cultivable, and only one-third of that is irrigated. And of the irrigated portion, they say, one-third has been harmed by excessive use of fertilizers.
Iraq and Syria almost went to war in 1975, Dr. Starr said, when Syria reduced the flow of the Euphrates to fill its largest dam. Similarly, Turkey claimed in the mid-1980s to have uncovered a Syrian plot to blow up Turkey's giant Ataturk Dam project further up the Euphrates.