In a so-called "Tripoli Declaration", the trio of Maghreb countries stressed the importance of "strengthening coordination and exchanges to ensure sustainable use" of the non-renewable source of fresh water.

The Northwestern Sahara Aquifer System is one of the world's largest groundwater reserves and has been exploited for centuries via springs and surface wells.

An increasing number of boreholes, which reach as far as 1,000 metres (3,300 feet) below ground, are increasing the extraction rate.

At the end of April 2024, Tunisian President Kais Saied, Algerian President Abdelmadjid Tebboune and Mohamed el-Menfi, head of the Libyan Presidential Council, agreed to create a "consultation mechanism" to manage the sharing of the water.

Just under two-thirds of the underground reserves, estimated at more than 40 trillion cubic metres of fossil water, are located beneath Algeria, with a little under a third below Libya and eight percent beneath Tunisia.

The mechanism, which was launched on Wednesday, is also intended to prevent pollution and overexploitation of the water.

On the basis of mathematical models, "each country will be allocated a quota. Water levels will be monitored, as well as other risks such as environmental pollution," Hussein al-Talou, head of research at the Libyan Ministry of Water Resources, told AFP.

"Management and monitoring will be carried out jointly by the three countries," he said.

Libya is one of the driest countries in the world and relies on the colossal, Gaddafi-era "Great Man-Made River", which transports fossil water from the south via giant pipelines, for 60 percent of its water.