This watering trees bit has had me flustered, and to be honest one of the reasons I've not tried it yet. Yesterday I brainstormed ways to provide water to the trees first when they were planted to help make sure the soil was solid and tamped down with no air pockets, and secondly to provide additional water in between rains. My guessing is that the ability to provide water on a reasonably consistent basis in the first year or two of the fruit tree's existence would further their chances of survival, in addition to taking all needed precautions to avoid critter damage etc.

Options: there are 2 wet weather creeks that run right next to and about 50 yards away from where I had planned on planting.
The property owners house is on the property(but not near enough run multiple hoses/power. I have access to water should I want to try and fill a tank. Wet weather creeks have steep drop offs, nearly waterfall type where I'm looking.

Original idea. Construct a rain barrel irrigation system, using the wet weather creeks to full rain into the barrels. As needed, use hoses and multiple 55 gallon drums.

2nd idea (having seen Kbush's post) I cannot get a truck to these locations, I don't own a 4 wheeler. Would a 12v pump have the ability to push water 100 yards uphill? This got me thinking, I've got a generator for emergencies that needs to be run under load regularly (as instructed by the manufacturer) a 110 v pump in a 55 gallon drum running off the generator providing a steady stream of water to the trees. I can fill the drum at the property. Any thoughts? This option seems to be perhaps more expensive (though not by too much) but probably more an efficient use of my time. The big question would be how much pump do I need?

All in all, If I watered twice a month it's a pretty easy cost to justify, and the property is about 20-30 minutes from the house so not a super imposing drive.