how does one, determine if water has been tampered with....
Just look for dead bodies....thousands of them.If not more.
Mumbles had the police dust for prints...
“how does one, determine if water has been tampered with....”
To give a literal answer to a rhetorical question: competent technicians could test numerous samples of the water for contamination and radiation. But the MWRA doesn’t actually say they did that. They seem satisfied with surface appearances, which doubles down on your question. “MWRA says it doesn’t APPEAR anyone tried to tamper with the water supply and there does not APPEAR to be any contamination or changes in water quality...” At least we can feel safe that there were no visible corpses or glowing warheads.
Water is normally tested daily entering the public system!
And is also tested coming out of the treatment plant!
I would think testing would be stepped up! That said it would be hard to contaminate the entire reservoir, however if the location of inlet to the water supply is known the perp can introduce chemicals at the inlet and pose a problem!