The Great Man-Made River, a $33 billion irrigation system built by Moammar Gadhafi to provide water from a vast underground aquifer in the desert for Libya's people, could become a crucial element in his fight to preserve his embattled regime.

The GMMR, as the project is known, is the crowning glory of Gadhafi's four decades in power. Hailed as a masterpiece of engineering, it provides 176.5 million cubic feet of water a day to the cities along the Mediterranean coast in northern Libya where most of the country's 6.5 million people live.

Libya's one of the driest countries in the world. Only 5 percent of the land gets at least 4 inches of rainfall a year but in the mid-1950s Western oilmen found vast underground lakes of clean groundwater trapped for millions of years.

The water comes from the Nubian Sandstone Aquifer, the largest in the world, covering 772,000 square miles 1,600-2,500 feet under the Sahara Desert across Chad, Egypt, Libya and Sudan. At 2007 consumption rates, the aquifer could provide water for 1,000 years.

Right now, control of the water supply appears to be in the hands of Gadhafi's beleaguered regime in Tripoli.

Should the unpredictable strongman, whose ruthless streak has kept him in power since 1967, choose to turn off the taps that supply rebel-held cities in eastern Libya, such as Benghazi, the result could be shattering.

The water is carried from the desert through a network of concrete tunnels around 3,125 miles long and buried 10-12 feet under the sand.

Western military sources say that the commanders enforcing the NATO-led no-fly zone over Libya to aid the rebels and pressure Gadhafi, branded a tyrant and supporter of international terrorism for much of his rule, to relinquish power fear he could be hiding tanks and missiles in the 15-foot-wide tunnels.

At present, the tunnels fall outside the parameters of the U.N.-mandated no-fly zone but NATO forces have been steadily widening their airstrike targets and using more destructive bombs and missiles against Gadhafi's military facilities.

"Western intelligence officials have now suggested that the concealment of heavy weapons in the tunnels is causing them problems, not least because strategic targets like these, which Britain and France would like to hit, fall outside what was agreed by the U.N. Security Council to protect Libyan civilians," Middle East analyst Ian Black wrote in the U.K. newspaper The Guardian.

Talk of hitting the GMMR may just be part of the psychological warfare being perpetrated against Gadhafi in hopes of convincing him to throw in the towel.

But it wouldn't be the first time he's gone underground to hide important facilities from his enemies.

During the 1990s, North Koreans built chemical weapons plants under a mountain at Tahuna, 50 miles southeast of Tripoli.

The plants were eventually abandoned, but at the time Libya claimed those tunnels were part of the GMMR.

The Libyan regime has warned that NATO airstrikes could trigger a "human and environmental disaster" if they damaged the GMMR tunnels.

Project manager Abdelmajid Gahoud told a news conference in the control center in Tripoli that between Benghazi and Sirte, Gadhafi's hometown in eastern Libya, oil and gas pipelines run parallel to the water network.

"If one of the pipelines is hit, the others are affected as well, which could mean a humanitarian catastrophe," he warned.

"If part of the infrastructure is damaged, the whole thing is affected and the massive escape of water could cause a catastrophe" that could leave as many as 4.5 million Libyans without drinking water as summer approaches.

On a wider canvas, water in the Middle East is a strategic asset. As water supplies are depleted because of overuse as populations swell and because of global warming, there are fears this vital commodity could trigger conflict.

The GMMR holds out the prospect of turning large tracts of Libya's desert into arable land and might one day eclipse Israel and Egypt as exporters of citrus fruit and other products to Europe.

"In 20 or 30 years, Libya could surpass both of them," one analyst observed. "There are several elements to the Libyan mess. One of them is certainly water."