I'm not so much concerned about our troops who can take some precaution. I'm concerned about a huge civilian population and the political fallout that could come from this.
I am certain the water will be tested immediately, and if any suspicious contaminants are in it they will announce it.
We have not had control of Basra so the burden would be on the Iraqis, not us.
On the other hand, the Arab press makes stuff up about us anyway, so whatever happens is probably immaterial.
I still think we should take out Al Jazeera.