I have not read this article in it's entirety yet but previous articles reported that the chemicals were dumped directly into the streams.
I've never made meth, but from what I've read to make meth it takes anhydrous ammonia, (a gas), and ether. Unless they off load a semi-tanker of ether into the river, there just isn't enough volume to do the damage.
As I said, this is an emotional ploy, in the fashion of Greenpeace showing clearcuts or seal clubbing to raise donations. Only they don't want donations they want the people out. Rural cleansing, IMHO.