With 90-95% 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% of the population, forcing many more residents in the impoverished Gaza Strip to buy bottled water at a premium.
"There is a crisis. There is a serious deficit in the water resources in Gaza and there is a serious deterioration in the water quality," said Rebhi El Sheikh, deputy chairman of the Palestinian Water Authority (PWA).
The Gaza Strip, governed by the Islamist group Hamas and in a permanent state of tension with Israel, 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 km of stored freshwater – equivalent to the amount of water held in the Dead Sea – making an already bad situation much worse.
Children hold bottles of water after filling them from public taps in northern Gaza Strip (Photo: Reuters)
But the situation in Gaza is particularly acute, with the United Nations warning that its sole aquifer might be unusable by 2016, with the damage potentially irreversible by 2020.
Only 5 to 10% of the aquifer's water is presently deemed 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 NIS 45 ($12.50) each month – a large sum for most Palestinians in the area – to buy filtered water that she stores in a 500-litre 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. Israel says the blockade is needed to prevent arms from reaching Hamas, which is opposed to the existence of the Jewish state.
The United Nations estimates that more than 80% of Gazans buy their drinking water.
"Families are paying as much as a third of their household income on water," said June Kunugi, a special representative of the UN children's fund UNICEF.
Salt and sewage
With no streams or rivers to speak of, Gaza has historically relied almost exclusively on its coastal aquifer, which receives some 50-60 million cubic meters of refill each year thanks to rainfall and runoff 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. Locals 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 most households dig their wells in secret. Hired laborers erect large plastic sheets to try and 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 NIS 12,700 ($3,513) 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.
While Israel shares the polluted aquifer, which stretches all the way to Caesarea, about 60 kilometers (37 miles) north of Tel Aviv, the problem is less acute than in Gaza which is downstream. In addition, Israel can access water from the Sea of Galilee and the mountain aquifer that also spans the West Bank.
As Gaza borders the sea, the obvious answer is desalination.
Gaza already hosts 18 small plants, one treating seawater and the others water from brackish wells - most of them supplied by UNICEF and the OXFAM charity.
The Palestinian Water Authority has started work on two new seawater desalination plants and is planning to construct a third, larger facility, which is designed to produce 55 million cubic meters of water a year.
But with funding for the $450 million project still uncertain, construction is not due to start until 2017.
By that time, cash-strapped Gaza may not have enough electricity available to power the energy-intensive plants. The United Nations estimates that Gaza already needs an additional 100 megawatts of production capacity, even before the big water facility is built.
Israel is trying to drum up aid for the territory, the senior security official said, alarmed at the prospect of a looming water catastrophe and possible humanitarian crisis on its doorstep in a few years.
"We have talked to everyone we know in the international community because 1.4 million people will be without water in a few years," he said, asking not to be named because of the sensitivity of the issue.
He said Israel, a leader in the desalination industry, was helping to train a handful of Gazans in the latest water technology, which the Palestinian Water Authority confirmed.
Sheikh called on international donors to help fund energy, water and sewage projects, warning of disaster if nothing happened.
"A small investment is needed to avoid a bigger one and it is a humanitarian issue that has nothing to do with politics or security," he said.