If it was a ‘scooper’, it certainly wasn’t the LA reservoir
I don’t think the Hollywood Reservoir is big enough for scoopers.
The proximity to the Pacific pretty much assures that they’re using salt water.
To-wit (just found this):
https://ktla.com/video/firefighting-aircraft-scoop-up-ocean-water-to-battle-palisades-fire/10353376/
It was all helo last night and they did an amazing job knocking down the Hollywood fire. Fixed wing basically doesn’t night drop. It’s too dangerous. 120-150mph at 200’ at night in hilly terrain? Nope. There was a company in Colorado a couple of years ago that claimed they could do just that. On the very 1st night of testing... crash.
FWIW, NBC Channel 4 reported multiple times last night that the helicopters were being loaded at the Reservoir