Palm Trees in Tucson

[blueskyguy]

I'm housesitting for friends in this beautiful city and they've asked me to water their trees. They told me that when they first moved here several years ago, they watered an Acacia Tree to rapidly, loosening the roots and the tree toppled over. They also have several Palm trees, most of which are not very tall, but they do have one that is very tall, probably 50 feet or more. They're instructions to me were to water all the trees, including all the Palms, once a month for four hours at a time. But to water at a drip rate so as not to cause any of the roots to pull out of the ground and topple the tree. My only concern would be the very tall Palm. Does anyone have experience with tall Palm Trees, especially experience watering them?
Thank you very much.