"Just lake water" is a good thing, because that means it's not river water. If the river breaks into the city, it's all over.
The question involved what was in the water: is it a toxic soup?
A lot of rain has fallen into the Mississippi drainage. This is happening in slow motion.
The "just lake water" answer was in response to a reporter question about the water being akin to a vat of poison (chemicals).
I did see one good size plume of gasoline or oil in one arial shot. But I'm sure it doesn't amount to a serious risk, in context with all the other trouble in place.
Except that lake is fed by the Gulf. Not a good thing. Understand why you said so, but it is dire in either case.