"It may snow, it may rain... (but) hope is not a strategy," said Prime Minister Kyriakos Mitsotakis. "We must be prepared for the worst possible scenario."

With the southeastern Mediterranean particularly vulnerable to climate change, Greece is facing its greatest water shortage challenge in 30 years, officials said Thursday.

Addressing an event to mark the centenary of the Athens water supply and sewerage company (EYDAP), CEO Harry Sachinis spoke of a "10-year, 2.5-billion-euro plan" that includes diverting two tributaries of the River Achelous in western Greece, in addition to drilling and desalination projects.

The goal is "to ensure that (the greater Athens area) will never have a water supply problem for the next 30 years," Mitsotakis said.

EYDAP serves some 4.4 million people in the greater Athens area.

The company last year said there had been an "important" 6.2-percent increase in water consumption owing to high temperatures.

Greece had faced its worst water shortage crisis during the early 1990s, when Mitsotakis' father was prime minister.

The country now ranks 19th in the world in terms of water shortage risk, said Environment and Energy Minister Stavros Papastavrou.

From 2022 onwards, Greece's water reserves have fallen by about 250 million cubic metres a year, he said.

This has been accompanied by a 25-percent fall in rainfall, and a 15-percent increase in evaporation annually, he said.

"The data shows that after Cyprus, our country will face the highest water stress in southern Europe," the minister said, adding that more than half of Greece's population could be affected.

"The hydrological data... shows that the water shortage persists and is intensifying... all the measurements show that we cannot wait any longer," Papastavrou said.

Majority state-owned EYDAP has already announced plans to replace over 600 kilometres (370 miles) of old piping over the next four years.

The 500-million-euro Achelous tributary project is to be completed by 2029.

Another 150 projects worth over 320 million euros are currently underway in more than 40 islands, the minister said.

The plan also includes consolidating, with EU assistance, over 700 local water companies to tackle water loss and regulate irrigation, he said.

EYDAP and Thessaloniki water company EYATH will be expanded to absorb the majority of these companies, he said.

Network losses nationwide are currently as high as 50 percent, Papastavrou said.

"In Singapore and Israel, every drop is used two and three times," he said.

Eydap in 2024 posted a 28-percent fall in net profits to 14.6 million euros.

In the first semester of 2025, it recorded a net loss of 5.6 million euros.