Algae bloom that crippled Israel’s desalination plants raises water security concerns

The “carpet” of microalgae stopped five of Israel’s six desalination plants from working.

1 hour agoShareSaveAdd as preferred on GoogleKaty WatsonandJames Cheyne,Jerusalem

Anadolu via Getty Images A person fills a bottle with water from a tanker placed by Israel's Water Authority near Damascus Gate in Jerusalem, following the shutdown of five desalination plants (31 August 2026)Anadolu via Getty Images
Israel’s Water Authority used tankers to distribute water in Jerusalem at the end of August

A recent outage of nearly all of Israel’s major desalination plants has sparked concern over the country’s future water security, with experts warning the war in Gaza is making the situation worse.

A vast bloom of microalgae in the Mediterranean Sea that grew to 100km (62 miles) long and 7km wide at its peak clogged the filters of five of the six major plants that convert seawater into drinking water.

While they are now up and running again (although only at up to 50% capacity) the microalgae remains present after almost three weeks and there is real concern that something similar could happen again.

The microalgae is thought to have originated from the Nile Delta, with experts pointing to a northerly current around the coastal eastern Mediterranean that then swept it up to Gaza and Israel. Feeding off sunlight as well as nutrients in the water, it has since spread rapidly, driven by higher-than-normal temperatures in the Mediterranean Sea.

Some academics have suggested Israel’s destruction of Gaza’s sewage treatment plants in the war with Hamas is partly to blame.

“It’s early days, but we know that sewage is a nutrient and algae blooms at great rates when there’s lots of nutrients in its vicinity,” says Gidon Bromberg of the EcoPeace Middle East environmental group.

Bromberg says even before the war, Israel’s restrictions on what is allowed into Gaza meant the territory’s sewage plants were out of date.

“One of the reasons why modern sewer stream plants weren’t completed in Gaza was because in order to build and run [them] you needed equipment that the Israeli military has defined as dual use – that could be used by Hamas as a weapon,” he says, giving the example of cement.

Edo Bar-Zeev, a professor at the Zuckerberg Institute for Water Research at Ben-Gurion University, called what has happened an “unexpected mega event”.

“I’ve been in the field of sampling ocean water for around 20 years or so and it’s definitely unusual,” he said. “In most cases it comes and goes in a few days, maybe a week… and here it’s held on for a while.”

The six plants, which generate more than 60% of Israel’s drinking water, were hit by what Lior Gutman, spokesman for Mekorot, Israel’s national water company, called a “huge carpet of microorganisms”.

Some farmers were affected, although the majority of those who use recycled water for irrigation did not face any shortages. Neither did 99% of households, Gutman said.

AFP via Getty Images Wastewater flows across a beach and into the Mediterranean Sea in Gaza City, in the northern Gaza Strip (13 September 2026)AFP via Getty Images
About 40,000 cubic metres of sewage flows into the sea each day from Gaza, where most wastewater infrastructure has been destroyed

The fact that the water crisis was hardly noticed by Israelis is a stark contrast to the daily lives of Gazans, who struggle with clean water supplies after Israeli bombardment has destroyed 90% of the Strip’s water and sanitation infrastructure, according to a report by aid organisation Doctors Without Borders.

Israel has become a world leader in desalination plants, which convert seawater into drinking water. A combination of climate change and a growing population has led Israel to rely more and more on the plants, which are located mainly along Israel’s coastline.

What happened has made experts worried about how Israel’s desalination plants can be paralysed by something like microalgae. Israel is also a major exporter of desalination technology, with Israeli companies designing and building plants around the world.

“I think this is a wake-up call for everyone in the water sector and certainly everyone here in the Middle East where desalination has been a major development to help advance a level of water security,” said Gidon Bromberg.

IsraelIsrael-Gaza war

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