An ancient Bedouin law says that if your water cistern dries up because someone left the lid open in the desert heat, you have just cause to kill the guilty party.
"In the Middle East, for the last 5,000 years, most of the wars have been fought over water," Israeli Premier Benjamin Netanyahu told reporters recently.
"We are focused constantly on territory," Mr. Netanyahu said. "But what good is it to resolve the issue of land, if you leave the issue of water unresolved?"
Lack of headway in implementing the 1993 Oslo accords has kept officials from reaching the pivotal "final status" talks between Israelis and Palestinians. Water sharing is a key issue.
Unlike many other Israeli-Palestinian parleys that have fallen silent, however, the water talk has kept on running.
In general terms, the new air of cooperation promised by Oslo has become clouded since the change of government in Israel almost two years ago. Netanyahu ushered in a tougher attitude toward the Palestinians, promising to put Israeli security - including that of its water supply - first.
While his predecessors in the Labor government signed a 1995 accord that "recognizes Palestinian water rights in the West Bank," current Israeli negotiators say that water resources must stay under Israeli control.
Palestinians say that the land on which they hope to establish a state must include rights to water beneath it. As they see it, Israel is using more than its share, and is seeking to cement its hold.
Ariel Sharon, a former general who is now the influential minister of infrastructure, wants to hold large swaths of the West Bank not only to create "security zones," but to make sure Israel's water sources aren't jeopardized.
"We are standing above the most important aquifer of Israel," Mr. Sharon told reporters during a recent trip to the West Bank. The Palestinians, lacking in technical expertise, would damage water sources handed over to them, he says. "In just two years, they managed to destroy the aquifer in Gaza by overpumping. The danger is that they will overexploit our water dramatically."
But the reference to "our" water rankles Palestinians. As they see it, they shouldn't have to pay Israeli companies for their water or ask for permission each time they want to dig a well.
West Bank cities under full Palestinian control now receive their water from wells in those urban areas, where there are often shortages during the summer. But Palestinians in areas under partial or full Israeli control must buy much of their water from an Israeli company.
The Israel-Palestine Center for Research and Information (IPCRI), an independent think-tank in Bethlehem, says about 40 percent of the Arab villages in the West Bank have no running water at all: They draw their water from wells that often run dry.
"We are facing a real water shortage here, especially in the summertime," says Fadel Qawash, who represents the Palestinians in the water negotiations. "We need three times the total water we are using now. If the Israelis want to make the desert green, they can do it with their own water. They are the thirsty partner."
But Israeli officials point out that Israel is using steadily less water to grow crops, using recycled or treated wastewater instead. Palestinians, they say, must adopt similar methods.
"Let them reduce their allocations for agriculture," says Meir Ben-Meir, the Israeli water commissioner. In his office in Tel Aviv, Mr. Ben-Meir pulls out charts to show how Israel has diverted agricultural water to be used for drinking water only.
"The Israeli settlements are provided with water from inside Israel by a pipeline, and they would be dependent on the same resources if they were not based in the West Bank. They are not being supplied by Palestinian resources," Ben-Meir says. If Israel kept up with Palestinian demand for water, he says it would either have to harm their common water table or divert Israeli water resources to the Palestinians.
There are two very different sides to this story. Palestinians consume about 13 gallons of water a day per capita, compared with the 65 to 75 gallons consumed by Israelis, according to the US Agency for International Development. But Israelis worry that pollution and mismanagement could ruin water resources for both peoples.
The Palestinian list of complaints is long. Foremost is the inadequate amount of water available to them from existing wells. Oslo attempted to find solutions by providing more water through constructing new pipelines and drilling new wells. But Palestinians need Israeli approval for new wells or wastewater projects.
Palestinian officials say their Israeli counterparts have been stalling on decisions because the rest of the peace process is frozen. Israel says it simply can't keep up with demand. For example, Israel recently gave approval for new wells near Bethlehem, but two of them came up dry.
Israeli officials add that they have more than lived up to their promises, subsidizing water to the Palestinians. But they do contradict at least one concept outlined in the agreement.
"We are prepared not to speak about water rights, but about equality of supply for humanitarian use," Ben-Meir says. "I recognize needs, not rights. We are prepared to connect Arab villages to Israel as well, but I want us to retain sovereignty in one hand."
That perpetuates a broader Palestinian grievance: that Israel can interpret Oslo as it wishes, so that the Palestinian Authority never actually gains control but exists only to police people.
On this, too, either side can read into the agreement. The accords say Israel should transfer to the Palestinians all responsibilities for water in the West Bank "related solely to Palestinians." But there are few water-management issues that Israelis will see as unrelated to them. And like most other hot-button issues, the agreement says that "ownership" of water will be addressed in final-status talks.
Gershon Baskin, a water expert at IPCRI, says that arguing over rights is futile, since the aquifer that feeds Israel and the West Bank needs to be shared.
"Twenty-five percent of water used in Israel today is from that aquifer - it doesn't recognize the Green Line [dividing pre-1967 Israel and the West Bank]," he says. "The argument of water rights is a stupid argument. The real argument is one of economics."
In the future, he says, more water will have to be diverted from Israel toward the Palestinians, since it is they who will be providing most of the agricultural base for both populations. Israel, already moving toward high-technology and service, is increasingly less dependent on agriculture for its economy. But in 20 years, there will only be enough water to supply people with drinking water, he says. Nearly everything else will have to come from recycled sewage or desalination.
The latter is probably the most realistic choice. But it remains expensive, and water commissioner Ben-Meir says he has been unable to get the Israeli Treasury to make serious investments in it.
"Desalination has to begin now, both in Israel and in Palestine," Mr. Baskin says. "They could also set one up in Gaza" with the help of funds from donor countries, "but they're too busy arguing about water rights."