As Israel Floods Gaza’s Tunnels with Seawater, Scientists Worry about Aquifer Contamination

As Israel Floods Gaza’s Tunnels with Seawater, Scientists Worry about Aquifer Contamination

Israel’s military has begun injecting “high-flow” seawater into Hamas-built tunnels beneath the Gaza Strip as part of its attempt to “neutralize terrorist infrastructures.”

On 30 January, the Israel Defense Forces (IDF) confirmed that the plan to flood tunnels under the Gaza Strip, a strategy that has been the subject of rumours since December, is being implemented at a number of undisclosed locations. The IDF’s statement added that the move was a “significant engineering and technological breakthrough” and that locations were chosen so that “groundwater in the area would not be compromised.”

However, some water researchers are warning that flooding tunnels with seawater could have a devastating effect on Gaza’s already scarce freshwater supplies and might destabilize buildings. There are also concerns that flooding the tunnels could endanger many of the approximately 130 remaining Israeli hostages who were abducted by Hamas in its attacks of 7 October 2023. The hostages’ locations remain unknown. But one researcher& Nature spoke to says he suspects the impact of the flooding will be limited, because Gaza’s aquifer is already contaminated by seawater.

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The tunnels are a “spider web” of damp passageways dug in sandy soil, former hostage Yocheved Lifshitz told the media after she was released last October. One tunnel is 50 metres deep, according to Israel’s Ministry of Foreign Affairs, and some have several entrance shafts and are reinforced with concrete and equipped with power cables and piping. The tunnels are probably used to store weapons, as well as for holding hostages captive. They extend to almost every corner of the crowded and devastated 363-square-kilometre Gaza Strip.

Biggest concern

One of the biggest concerns is that seawater used to flood the tunnels will contaminate an important coastal aquifer, which lies between Gaza, Egypt and Israel and supplies nearly 80% of Gaza’s water.

Mark Zeitoun, a water engineer and director-general of the Geneva Water Hub in Switzerland, says that Gaza’s main source of drinking water is being contaminated. “If you put salty water into a freshwater source, it’s polluting, it’s contaminating, it’s poisoning,” he says.

There’s a possibility that the seawater, once pumped into the tunnels, will simply leak out, Zeitoun adds. “If you just try filling the tunnels with water, I assume that they’re not sealed well enough to hold any water. The water would drain out and into the aquifer,” he says.

Geographer Ahmed Ra’fat Ghodieh, based at An-Najah National University in Nablus in the West Bank, agrees that the aquifer is likely to become irreparably contaminated with salt water.

“If they flood these tunnels, then the seawater will penetrate the geological strata, towards the aquifer,” says Ghodieh. “Such action will have severe consequences on all aspects of life in Gaza — on agriculture, on soil, on infrastructure.” Ghodieh adds that the seawater could create sinkholes that destabilize the foundations of buildings.

But hydrologist Noam Weisbrod, who is dean of the Jacob Blaustein Institutes for Desert Research at Israel’s Ben-Gurion University of the Negev, says that those concerned that the entire coastal aquifer will be irreparably contaminated are probably overestimating the flooding’s effects. “I’m not sure that the environmental risk is as extreme as people want to believe,” he says. The impact of flooding would differ depending on where the affected tunnels are located, he adds.

The water level of Gaza’s coastal aquifer ranges from about 60 metres below the surface in the east to just a few metres deep near the coastline, according to a 2020 study published in the journal Water. More water is being drawn out of the aquifer than can be replaced naturally by fresh water, and as a result the aquifer is already being infiltrated by seawater.

Weisbrod’s reasoning takes into account the fact that, in areas close to the coast, the water in the aquifer is already saline. Moreover, he says, “large sections of the aquifer water are already contaminated from unregulated sewage systems, fertilizers and more”.

Weisbrod also says that Israel’s plan could have limited impact. The tunnel network “is not one big metro plan like in New York or in London,” he explains. “It’s not one big thing that is all connected. So, you’ll use a lot of effort and you’ll flood something quite limited, eventually. So maybe it’s not worth it.”

Gaza’s water crisis

The debate over the tunnels highlights a problem that existed before the flooding started: clean water is scarce in Gaza, irrespective of the extent to which the aquifer is contaminated by seawater pumping. In 2020, United Nations agencies estimated that 10% of the population had access to safe drinking water.

Some water is piped in by Israel and Egypt. A €10-million (US$10.9-million) seawater desalination plant funded by the European Union opened in Gaza in 2017, but it presumably cannot function without an electricity supply. Before the war, around half of Gaza’s electricity came from Israel, but, in October, the Israeli government cut off supplies.

Almost 1.9 million people have been displaced by the war, with many living in tents or on the streets in the southern Gazan city of Rafah. Following torrential rains in January, many are collecting drinking water in dishes and buckets, Ghodieh says. Others buy water from tanker trucks — low-quality water from the aquifer that has been desalinated by private companies — says David Lehrer, director of the Center for Applied Environmental Diplomacy at the Arava Institute for Environmental Studies in the Arava Valley, Israel.

When the war ends, Israel and Gaza need to start planning for a better water future, Lehrer says. In 2023, through a partnership with the Israeli company Watergen, the Palestinian non-governmental organization Damur for Community Development, and the Israeli Civil Administration, the Arava Institute installed five solar-powered atmospheric water generators at municipal health-care centres in Gaza. According to the Arava Institute, these can generate around 900 litres of clean drinking water per day by capturing humidity, condensing and filtering it.

This initiative, and other interim measures such as off-grid wastewater treatment, Lehrer says, will “provide a glimmer of hope that the situation will eventually improve.”

This article is reproduced with permission and was first published on February 2, 2024.


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