LONDON: The algae bloom that clogged intake pipes at Israel’s Mediterranean desalination plants in late August exposed the fragility of a water system that supplies not only Israel, but also Gaza.
Five of Israel’s six coastal desalination plants, which convert seawater into drinking water, shut down after microscopic algae clogged their intake systems, CNN reported on Sept. 4, citing Mekorot, Israel’s national water company.
The plants produce more than 80 percent of Israel’s drinking water, according to Israeli media.
Some privately owned plants have since resumed partial operations. But as of Sept. 3, only one was operating at full capacity. By Sept. 7, two plants remained closed and three others were operating at limited capacity for a ninth consecutive day, The Times of Israel reported.
Authorities responded by restricting water use, increasing withdrawals from reservoirs and the Sea of Galilee, and limiting supplies to agriculture, Haaretz reported.
Mekorot spokesperson Lior Gutman called the disruption unprecedented, according to CNN.
Scientists believe the bloom formed near Egypt’s Nile Delta before Mediterranean currents carried it north along Israel’s coast. The algae extended at least a dozen kilometers, said Edo Bar-Zeev, an associate professor of water research at Ben-Gurion University of the Negev.
“This is the first time I saw something of this extent,” Bar-Zeev, who has tested coastal water for two decades, told CNN.
Environmental experts say untreated sewage from Gaza may be worsening the nutrient-rich conditions in which algae thrive. Gaza’s six wastewater treatment plants have been damaged or destroyed during the war, allowing untreated sewage to flow into the Mediterranean for months.
Zalul Environmental Association, an Israeli nonprofit, said in a statement that satellite imagery suggested that pollution feeding the bloom came from both Gaza and the Nile Delta.
But for Palestinians in Gaza, the crisis did not begin with an algae bloom, but with the destruction of water and sewage infrastructure during the war, compounded by Israeli restrictions on supplies and movement.
Maysa Yousef, an artist and mother in central Gaza, said she first noticed green algae forming in bottles filled with Mekorot water, which is piped from Israel into Gaza through a network of transmission lines.
“Before Israel announced that the water had become contaminated, we already knew,” Yousef told Arab News. “Every morning, I filled the water bottles, then when I went to wash them in the evening, I found them all covered in algae.”
She said her husband initially dismissed her concern because the water came from Mekorot.
“I told my husband, ‘The water coming to us from Israel is contaminated. It is not clean,’” she said. “He said, ‘No, it is Mekorot water — it is desalinated and treated.’ I told him, ‘No, there is algae in it. Look inside the bottles.’”
Other Gaza residents have shared similar accounts on social media, reporting algae and small worms.
When Israel announced the desalination shutdowns in late August, Mekorot supplies to Gaza were cut off, Yousef said. For many families, the water had been one of the few comparatively safe sources available.
“Gaza relied on Mekorot water because it is close to drinking-water quality,” she said. “Some people drink it although it tastes awful.”
Her family used it for cooking and tea because safe drinking water was already scarce.
The World Health Organization said on Sept. 1 that microbiological contamination in Gaza water samples had risen from less than 6 percent in January to nearly 20 percent in August.
Since 2024, Gaza residents have faced severe water shortages. In many areas, people have reportedly resorted to makeshift latrines as sanitation systems failed.
Nearly 90 percent of Gaza’s water infrastructure, including desalination and wastewater treatment facilities, has been destroyed, according to UN agencies and media reports. Damaged sewage lines have also contaminated the aquifer on which many residents depend.
In February, the UN Office for the Coordination of Humanitarian Affairs said its partners reported that the Mekorot supply line was fully shut. The line had already been operating at reduced capacity because of two identified leaks, and repairs near a reservoir had not been completed.
Humanitarian groups have increased water trucking to affected neighborhoods, but access remains uneven. In Al-Mawasi, residents have complained that available water is visibly contaminated.
“If you put it in front of a donkey, it would refuse to drink it because it is so filthy and full of worms,” one local woman, whose name is being withheld at her request, said. “But we had no alternative. Otherwise, you die of thirst.”
The WHO warned in early September that Gaza’s deteriorating water quality was raising the risk of disease outbreaks. Winter rains could further spread sewage and contaminated water through overcrowded displacement sites, the agency said.
Reinhilde Van de Weerdt, the WHO representative for the Occupied Territories, said microbiological contamination found in water samples had nearly tripled since the beginning of 2026.
Cases of acute watery diarrhea nearly doubled, from about 30,000 in March to more than 58,000 in August, she told a weekly briefing in Geneva.
Yousef said her husband was among those who became ill after drinking contaminated water.
“About two weeks ago, my husband started having stomach pains,” she said. His condition worsened and he needed to go to the hospital. With no transportation available, the family walked to Al-Aqsa Martyrs Hospital in Deir Al-Balah.
At the hospital, she said, care was being delivered in tents and essential services were scarce. After running tests, they discovered that he suffered from an inflammation of the stomach lining caused by consuming contaminated water.
“Now he is forbidden from drinking water except imported bottled drinking water,” Yousef said. “No coffee, no soft drinks, and only limited vegetables and fruit, and so on.”
Gaza’s health system has been devastated by the war, with hospitals and other medical facilities damaged or destroyed and restrictions limiting the entry of medicines, medical supplies and fuel.
For Gaza’s residents, the algae bloom was not an isolated environmental disruption but another sign of a broader collapse: a water system already battered by war, damaged infrastructure and the loss of basic public health protections.