1) How much water was released during the dam failure?
12.6 billion gallons of water was released into the canyon.
2) How were people downstream warned of the coming flood, once people realized what was happening?
Phone operators phoned communities in the path and highway patrol members rode around with sirens.
3) Take a little tour in Google Earth in the region, by searching for St Francis Dam. From your search, can you figure out how the water is now stored in this region to serve LA?
From living in CA I know a majority of water comes from the Colorado. The bypass of the Saltan Sea near Indio is one reason the “sea” is drying up. I noticed various aqueducts around LA, but as far as storing the quantity of water they need I did not find a location so I googled it. The LADWP website lists water coming from the Colorado, California Aqueduct from NorCal and ground water, but I could not find an actual answer as to storage. The LADWP does list Lake Oroville in NorCal but that seems to be to far away for storage considering it takes 16 days for water to travel the length of the aqueduct.