Israel is believed to monopolise about 75% of Palestinian water resources in a region where rainfall is infrequent and water a strategic asset.
In the agriculture-dependent Palestinian territories, hemmed in by Jewish settlements, the lack of resources causes havoc for farmers, while pollution and inadequate waste disposal create manifold sanitation and health problems.
In the northern West Bank town of Nazlet Isa, giant concrete slabs 10 metres high - lambasted as an apartheid wall by the Palestinians - have left six homes stranded on the Israeli side along with the rich underground aquifer.
A special system of pipes to access the water was finally built with Israeli permission, but immediate access and control has passed into other hands.
Elisabeth Sime, a director of aid organisation CARE International in the Gaza Strip and West Bank, said: "The route of the wall matches that of water resources, the latter being conveniently located on the Israeli side."
"The route of the [Israeli]wall matches that of water resources, the latter being conveniently located on the Israeli side"
The Palestinians are adamant that the wall - which they view as a land grab designed to delimit the borders of their promised future state - was built deliberately to siphon off the aquifer.
Israel says it was built for security reasons to prevent suicide bombers infiltrating Israel or Jewish settlements.
But Hind Khury, a former Palestinian cabinet minister responsible for Jerusalem and now the government's representative in Paris, charged that "with the wall, the Israelis clearly sought to commandeer water resources."
No water, no life
"Without water, there is no life. Israeli policy has always been to push Palestinians into the desert," he added.
Abdul Rahman Tamimi, director of the non-governmental Palestinian Hydrology Group (PHG), said the coincidence of the route of the wall with the layout of the region's aquifers was not by accident.
"The wall cuts some communities off from their only source of water, prevents tanker trucks from getting around and puts up prices," he said.
In Qalqilya, in the northern West Bank, about 20 wells, or 30% of the town's resources, were lost because of the wall, Tamimi says.
While agriculture accounts for nearly a third of Palestinian gross domestic product, only 5%of Palestinian land is irrigated.
Israel's separation wall steals
arable Palestinain land
On the other hand, 70% of Israeli and Jewish settlement land is watered, even if agriculture amounts to barely 2% of Israeli GDP.
"The fact that Israel confiscates and overexploits water affects every sector of Palestinian economic life and causes problems for the chances of development in the region and therefore chances of peace," Tamimi said.
More than 220 communities in the West Bank - nearly 320,000 people - are unconnected to mains water.
Hundreds of thousands of Palestinians therefore buy water from trucks - an expense many can ill afford - to supplement local supplies that often fall woefully short of requirements.
One such consumer is 76-year-old Nazmi Abdul Ghani. Clutching clumps of soil and turning to the heavens, the grandfather of 100 is desperate. "I can't go on like this. My land is parched and I'm ruined."
One of the respected of the northern West Bank village of Saida, he uses expensive water tankers to irrigate his tomatoes, onions and potatoes.
"The Israelis stole our land and took our water," he rages.
In the small town of Attil, at least a third of the local drinking water is contaminated by sewage and pesticides. Nine-year-old Fatima, her eyes misted with fever, routinely falls sick.
"The fact that Israel confiscates and overexploits water affects every sector of Palestinian economic life and causes problems for the chances of development in the region and chances of peace"
Abdul Rahman Tamimi, Palestinian Hydrology Group
Waste and faeces from neighbouring houses run down the hill and seep through the floors and walls of Fatima's home. They slowly eat away at its foundations and emit a strong stench.
"I often get stomach ache. I throw up. It's the same for all the children here," she says looking feverishly at her mother Awa.
Doctor Hossam Madi says diarrhoea, gastroenteritis, fever, kidney failure, infection and dermatological problems blight most Palestinian children and persist into adulthood because of poor water supplies.
"The quality of water is getting worse and worse," said CARE's Sime.
"A high proportion of new-born babies die of water-born infections. In the long run, Israelis will be affected by the pollution of water in the Palestinian territories."
Inadequate water affects the
health of Palestinian children
In villages such as Jalbun, household, agricultural and industrial waste from Israeli settlements speed up the process of water pollution.
Tamimi accuses some Israeli business people and settlers of dumping toxic waste on Palestinian land in an act of "environmental terrorism".
Water supply problems faced by Palestinians are unfortunately typical of those hoping to be dealt with at the World Water Forum, which opened in Mexico City on Thursday.
The March 16-22 forum hopes to help shape global strategy to improve distribution and eradicate waste of the precious resource that increasingly leads to conflict.