BAGHDAD - Authorities in Iraq have issued a contingency plan for the possible collapse of the Mosul dam amid fears that the lives of almost 1.5 million people along the Tigris river could be at risk from catastrophic flooding.

The statement is the first public acknowledgment by the Iraqi government of the danger posed by the dam, which is in a poor state of repair after years of neglect and its brief capture by Islamic State (IS) fighters in 2014.

The government earlier this month awarded a contract to Italian engineering firm TREVI to undertake emergency repairs on the 3.4km dam, which is the fourth largest in the Middle East and lies 40km north of Mosul, Iraq’s second city which is currently controlled by IS.

Many other Iraqi cities including Baghdad, the capital, Shirqat, Baiji, Tikrit, Samarra, Balad and Dujail could be flooded if the dam breaks down, Iraqi and US officials warned.

“The collapse of the dam is very unlikely, especially with the technical and administrative precautions taken by the authorities, but the serious consequences if it did happen necessitate the alert,” Iraqi Prime Minister Haider al-Abadi’s office said in a statement on Sunday.

“We have developed a package of precautionary recommendations, in order to avoid any potential risk, God forbid. They [the recommendations] have to be taken into consideration by all people.”

The US embassy in Baghdad on Sunday also issued an alert to US citizens warning them of the dangers of a possible collapse.

It said that Mosul could be inundated by more than 13 metres of water within hours of a breach and that downriver cities including Tikrit, Samarra and Baghdad would face lower but “still significant” levels of flooding within 24 to 72 hours.

“We have no specific information that indicates when a breach might occur, but out of an abundance of caution, we would like to underscore that prompt evacuation offers the most effective tool to save the lives of the hundreds of thousands of people living in the most dangerous part of the flood path in the event of a breach,” the embassy said.

In an assessment of the possible impact of a breach of the dam, the US embassy said that nearly 1.5 million Iraqis would likely be killed by an "inland tidal wave" unless they were moved to safe areas.

It also said that because much of the territory likely to be badly affected by a breach was controlled or contested by IS, "an authority-directed evacuation is unlikely" and some evacuees would not have sufficient freedom of movement to escape.

"Mosul dam faces a serious and unprecedented risk of catastrophic failure with little warning. A catastrophic breach of Iraq’s Mosul dam would result in severe loss of life, mass population displacement, and destruction of the majority of the infrastructure within the path of the projected floodwave," it said.

“The approximately 500,000 to 1.47 million Iraqis residing along the Tigris river in areas at highest risk from the projected flood wave probably would not survive its impact unless they evacuated the flood zone.

“A majority of Baghdad’s six million residents also probably would be adversely affected - experiencing dislocation, increased health hazards, limited to no mobility, and losses of homes, buildings and services.”

The dam, which opened in 1986, needs constant maintenance because of structural flaws in its foundations that require regular re-grouting with cement.

But that process was interrupted for eight weeks in 2014 when IS overran the dam and surrounding areas.

Security for TREVI employees currently working to repair the dam is being provided by Kurdish peshmerga forces supported by 450 Italian troops who were deployed to the site in December.

An assessment of the dam conducted by a US army engineering team in Iraq earlier this month for the Iraqi parliament and seen by Middle East Eye said: “All information gathered in the last year indicates Mosul Dam is at a significantly higher risk of failure than originally understood and is at a higher risk of failure today than a year ago.”

Until Sunday the Iraqi government had publicly denied any possibility that the dam could collapse and had challenged the earlier warning issued by the US team.

Iraq's Ministry of Water Resources, which is in charge of the country’s dams, played down the US assessment and argued that similar warnings had been issued in 2005, 2006 and 2007.

“The dam will be safe as long as the water level is low,” it said.

'Routine warning'

The dam’s reservoir has a capacity of 11.5bn cubic metres, but currently holds no more than 4.5bn cubic metres, Iraqi officials told MEE.

“Maintenance work is ongoing, the situation is under control and the current inventory is equivalent to just one-third of the tank's capacity,” Mahdi Rasheed, the general director of the Iraqi Dams Company, told MEE.

"The [contingency] plan is a routine warning to educate people about this issue, so people will be sure that everything will be okay."

But an extensive investigation conducted earlier this month by the parliamentary committee of water and agriculture concluded that water levels were expected to rise significantly in March and April and that the “stress on the dam will be increased”.

The parliamentary report recommended “seeking quick solutions for drainage” and stressed that “decreasing the level of water in the reservoir to the minimum would decrease the impact of the wave of flooding if the dam collapsed but will not completely prevent damage, so a contingency plan has to be prepared”.

Sunday’s statement included an “instruction manual” informing citizens about the likelihood of the dam collapsing and advising them what to do in the event that it did.

It said the scale of any disaster would be affected by water levels in the reservoir and along the Tigris river at the moment when the dam failed.

It said the current guidance was based on an assumed water level in the reservoir of 319m, while the current level was 307m which “reduced risk substantially, especially in Baghdad”.

According to the guidance, all cities, towns and villages located along the banks of the river would be “severely” impacted, with residents requiring relocation.

Mosul, 400km north of Baghdad, would be the most badly affected city, with water levels in some areas reaching 15 metres between one and four hours after the collapse of the dam.

Flooding would reach Tikrit within one or two days, and Baghdad within three or four days with water levels in the capital possibly reaching 10m, “although at current water levels the damage would be less”.

The guidance tells people to move as far away from the Tigris and its tributaries as possible and to head for higher ground.

The recommended distance to safety for Mosul residents is 6km, for Samarra residents 6.5km and for Tikrit 5km.

"The best way to be safe, is to move to higher areas," it said.

US State Department documents assessing Mosul dam safety: