Something you probably wouldn't expect in that valley is a golf course. A fine one, definitely. But that comes with the risk of getting hit by flying golf balls. I came across this sign on the walk up to Hotel Villa Engiadina in Vulpera.
Hm, I could imagine other dangers in high mountain areas ...
While hiking in the Engadine, you are surrounded by crystal clear streams, rivers, and waterfalls. Do not fill your bottle from any of them. If you do not see cows around you, do not be fooled. They are taken to the high pastures for much of the summer. There is 99% certainty that the water has cow dung in it.
Fill your bottles from the fountains in town squares or from your hotel tap -- it will be delicious. Resist the temptation to put lovely cold stream water into your bottle, though.