Libya, Algeria and Tunisia have signed a landmark agreement to jointly manage one of the world’s largest underground water reserves, pledging a “rational and equitable” use of the vast North-Western Sahara Aquifer System that lies beneath all three countries.

The accord, known as the Tripoli Declaration, commits the neighbours to closer coordination, data sharing and long-term planning to safeguard what experts describe as a fragile, non-renewable resource. The aquifer, a colossal store of fossil water accumulated over thousands of years, underpins agriculture, drinking supplies and urban growth across swathes of North Africa.

Libya’s minister of water resources, Hosni Aouidat, said the agreement responds to mounting pressures on the region’s scarce water. He cited climate change, rapid population growth and rising demand as forces that “require us to redouble our efforts and strengthen coordination and integration among ourselves.”

Hydrologists estimate the aquifer holds more than 40 trillion cubic metres of water. Nearly two-thirds of that volume lies under Algeria, just under a third beneath Libya and around eight percent under Tunisia. For decades, the resource has been tapped through springs and shallow wells, but the spread of deep boreholes, some plunging 1,000 metres, has sharply accelerated extraction.

Under the new mechanism, the three states will use mathematical models to determine how much water each can safely withdraw. “Each country will be allocated a quota,” explained Hussein al-Talou, head of research at Libya’s Ministry of Water Resources. “Water levels will be monitored, as well as other risks such as environmental pollution.”

The agreement also sets out joint monitoring and management structures designed to curb overpumping and contamination from agriculture, industry and urban waste. Officials say regular exchanges of technical data and field measurements will be central to preventing irreversible damage to the aquifer.

The stakes are particularly high for Libya, one of the driest countries on earth. Its cities and farms depend heavily on the Great Man-Made River, a vast network of pipelines built under Muammar Gaddafi to transport fossil water from southern desert wells to the Mediterranean coast. Any decline in the aquifer’s levels or quality could have far-reaching consequences for food security, public health and regional stability.

By formalising cooperation, Libya, Algeria and Tunisia are positioning shared water management as a pillar of regional diplomacy, betting that collaboration beneath the sands can help avert future conflicts above them.