Sensors installed by American army engineers in December 2015 show widening fissures in the fragile gypsum base underneath the Mosul dam, though no one can predict when a breach might occur….The Iraqi government has now contracted with the Trevi Group, an Italian firm, which it hopes will offer a more advanced and permanent method of plugging cavities in the stone base than the constant maintenance it has required for the past 30 years. That maintenance came to an abrupt halt after IS seized the dam in August 2014, and has continued only intermittently after it was seized back three weeks later. Essential equipment went missing then, and half its staff decided not to return to work.
One study says that if the dam collapses, Mosul would be submerged within hours. Another warns that half a million Iraqis could be killed by floodwaters, and more than a million forced from their homes. Disease and looting as the floodwaters raced through Baiji, Tikrit, Samarra and even parts of Baghdad would complete that dreadful scenario.
The dam was built by an Italian-German consortium and started operating in 1986. Because of the high proportion of gypsum in the area, the construction included a grouting tunnel to allow almost constant injection of cement and drilling mud into crevices in the base that are widened by the water flowing through them. America’s Army Corps of Engineers warned in 2005 that the “extraordinary engineering measures” needed to maintain its structural integrity made the structure potentially the most dangerous in the world.*** But taking the dam out of commission is not an attractive option. Emptying the reservoir would leave Iraqis seriously short of drinking and unpolluted irrigation water in the summer.
Excerpts from The Mosul dam: A watery time-bomb, Economist, Feb. 13, 2016, at 42
*** The dam was constructed on a foundation of water soluble gypsum!!! More than 50,000 tonnes of material have been injected into the dam since leaks began forming shortly after the reservoir was filled in 1986, and 24 machines currently continuously pump grout into the dam base. Between 1992 and 1998 four sinkholes formed downstream of the dam and a fifth sinkhole developed east of the dam in February 2003 which was filled several times. In August 2005 another sinkhole developed to the east (Wikipedia).