I have two 3,000 gallon tanks in a Quonset along with a electric 10 horsepower 3" pump.  The tanks have floats in them to keep them full in the summer time.  I can load my tender trailer with 5,000 gallons of water in about 20 minutes and can send someone else to the yard to do it without worrying about them starting a motor.....or I can call my wife or kids and have them do it.  It was not a cheap thing to setup when I did it but having access to water quickly makes spray planning significantly easier.  If my yard were laid out differently I probably would have put everything outside and in a black tank but didn't fit well for truck traffic.