If the Mosul Dam fails, a wall of water will sweep into Iraq's third largest city with a population of 1.7 million (photo: CNN)

As world attention focuses on the daily slaughter in Iraq, a devastating disaster is impending in the north of the country, where the wall of a dam holding back the Tigris river north of Mosul city is in danger of imminent collapse.

"It could go at any minute," says a senior aid worker who has knowledge of the struggle by US and Iraqi engineers to save the dam. "The potential for disaster is very great."

If the dam does fail, a wall of water will sweep into Mosul, Iraq's third largest city with a population of 1.7 million, 20 miles to the south. Experts say the flood waters could destroy 70 per cent of Mosul and inflict heavy damage 190 miles downstream along the Tigris.

The dam was built between 1980 and 1984 and has long been known to be in a dangerous condition because of unstable bedrock. "The dam was constructed on a foundation of marls, soluble gypsum, anhydrite, and karstic limestone that are continuously dissolving," said specialists at the US embassy in a statement. "The dissolution creates an increased risk for dam failure."

In fact the state of the two-mile long earthfill dam, which holds back some eight billion cubic metres of water in Iraq's largest reservoir, has recently been deteriorating at ever-increasing speed. According to one source, the chance of a total and immediate failure of the dam is now believed to be "reasonably high" at current water levels and "most certain" within the next few years.

The effort to prevent the collapse of the dam is overseen by the Iraqi Ministry of Water Resources. The US Army Corps of Engineers has made continual efforts to monitor the deterioration and undertake remedial action. But a US report, obtained separately from the embassy statement, says that "due to fundamental and irreversible flaws existing in the dam's foundation, the US Army Corps of Engineers believes that the safety of the Mosul Dam against a potential catastrophic failure cannot be guaranteed".

Iraq, the site of the biblical flood, is very vulnerable to inundation because it is very flat south of the Kurdish mountains. Prior to the building of dykes and other control measures in the early 20th century, there were frequent disastrous floods when snow melted in the mountains of Turkey.

The great majority of Iraqis live along the Tigris and Euphrates. If the dam does break, specialist sources say that the impact of the flood would be felt all along the Tigris river valley. This would mean heavy damage to cities such as Tikrit and Samarra and the floods could reach as far as Baghdad, home to six million people, though by then the force of the floodwaters should have dissipated.

Given that the Iraqi government has only intermittent control of this area north of the capital, which is overwhelmingly Sunni, it is unlikely it could undertake effective measures to save lives if a flood occurred.

The main method used to strengthen the foundations of the Mosul dam is pumping liquid cement into it or grouting. But a US-funded study concluded that grouting would not save the dam although it did need to be continued and enhanced "to reduce the probability of failure". An international panel of experts called in by the Ministry of Water Resources in Baghdad concluded that a limit should also be placed on the level of the water in the reservoir - that was done in April last year.

The ministry did not respond to inquiries by email and phone about the deteriorating state of the dam. "It is a time bomb waiting to go off," said the aid worker.

"Everybody knows about the threat but they have other preoccupations and, in the case of foreigners, it is now conveniently in Iraqi hands." He said that on some US communications equipment, there was a panic button to be pressed as soon as the dam began to give way. The unstable bedrock beneath the dam has been known about for a long time. The Iraqi government has been trying to patch it up for 19 years. It is not clear why the dam, known as the "Saddam Dam" prior to 2003, was built where it is, given the solubility of the rock underneath it. The fact that construction began in 1980, the first year of the Iran-Iraq war, and the reservoir began to fill only four years later, may explain why such a gross error about its site was made.

Saddam Hussein began a period of helter-skelter construction in the first years of the Iran-Iraq war to show his people the conflict would not hold back economic development. The construction boom, funded by loans from Saudi Arabia, Kuwait and the UAE, involved too many new projects for Iraq to monitor effectively. The dam has an installed hydroelectric capacity to produce 750MW of electricity and its other functions are flood control, the supply of water for irrigation and municipal water supply. Given the chronic shortage of electricity in Iraq there is a disinclination to reduce the amount coming from the Mosul dam or any other source.

The weakness of the dam became evident soon after it was built. The US embassy statement says: "To manage the risk, the Iraqi Ministry of Water Resources has been conducting continuous grouting operations to fill voids and fractures created by the dissolution of the foundation since the 1980s."

None of the measures have proved to be enough so far, although the US government is worried enough to provide construction materials, equipment and spare parts. The UN's Food and Agriculture Organisation has also provided equipment for grouting over the past year.

If the dam breaks it will be deeply damaging to the Iraqi government and the US authorities in Iraq because the disasters of the past four years are already seen by Iraqis as evidence of their inability to rule Iraq effectively.

http://news.independent.co.uk/world/middle_east/article2843961.ece