With 90 to 95 per cent of the territory's only aquifer contaminated by sewage, chemicals and seawater, neighborhood desalination facilities and their public taps are a lifesaver for some of Gaza's 1.6 million residents.

But these small-scale projects provide water for only about 20 per cent of the population, forcing many more residents in the impoverished territory to buy bottled water at a premium, a new report by the Independent said.

The UN estimates that more than 80 per cent of Gazans buy their drinking water. "Families are paying as much as a third of their household income for water," said June Kunugi, a special representative of the UN children's fund Unicef.

The Gaza Strip, governed by the Hamas movement and in a permanent state of tension with Israeli occupying regime, is not the only place in the Middle East facing water woes.

A Nasa study of satellite data released this year showed that between 2003 and 2009 the region lost 144 cubic kilometers of stored freshwater – equivalent to the amount in the Dead Sea – making a bad situation much worse.

But the situation in Gaza is particularly acute, with the UN warning that its sole aquifer might be unusable by 2016, with the damage potentially irreversible by 2020. Between 5 and 10 per cent only of the aquifer's water is safe to drink, but even this can mix with poor-quality water during distribution, making it good only for washing.

"The tap water from the municipality is not fit to drink, and my husband is a kidney patient," said Sahar Moussa, a mother of three, who lives in a cramped, ramshackle house in Khan Younis in the southern Gaza Strip, near the Egyptian border. She spends 45 shekels (£8.20) each month – a large sum for most Palestinians in the area – to buy filtered water that she stores in a 500L plastic tank.

Further complicating the issue is Israel's blockade of the Gaza Strip, which activists say has prevented the import of materials needed for repairs on water and waste facilities.

With no streams or rivers to speak of, Gaza has historically relied almost exclusively on its coastal aquifer, which receives some 50 to 60 million cubic meters of refill each year thanks to rainfall and run-off from the Hebron hills to the east. But the needs of Gaza's rapidly growing population, as well as those of the nearby Israeli farmers, means an estimated 160 million cubic meters of water is drawn from the compromised aquifer each year. As the levels sink, seawater seeps in from the nearby Mediterranean. This saline pollution is made worse by untreated waste, with 90,000 cubic meters of raw sewage allowed to flow into the shallow sea waters each day from Gaza, according to UN data.

Even with the aquifer, regular running tap water is a luxury unknown to many Gazans. People living across the territory say that during the summer months water might spurt out of their taps every other day, and the pressure is often so low that those living on upper floors might see just a trickle.

Many families have opted to drill private wells drawing from water deep underground. Authorization is required but rigid restrictions mean that most households dig their wells in secret. Hired laborers erect large plastic sheets to try to hide their work from prying neighbors. "As you can see, this is like a crime scene," said a 45-year-old father of six, who gave his name as Abu Mohammed. A clothes merchant from Gaza city, he paid his clandestine, seven-strong crew £2,300 to drill a well and came across water at a depth of 48 meters. "We begin the work after sunset and... cover the sound of digging with music," he said. A senior Israeli security official estimates that as many as 6,000 wells have been sunk in Gaza, many without authorization.