The increased drainage pushed the Jianjiang River out of its banks, but officials hoped minor flooding now would prevent a catastrophic flood later on, if the dam were to collapse.
An unknown number of people were evacuated in Jiangyou City ahead of the increased outflow, Xinhua reported.
If the dam were to break, it could threaten up to 1.3 million people downstream. More than 250,000 people already have been been evacuated, Xinhua reported.
http://edition.cnn.com/2008/WORLD/asiapcf/06/10/china.quake/index.html
Is the future meaning introduced by "were to" necessary? Would it be bettter to use the simple past "If the dam broke"?
Thanks