Will my large outdoor plants need more than 5 gallons of water a day?

I am trying to determine how much water I will need during the summer months. Since I plan on 1,000 plants I am concerned I might need some water rights. Not overly concerned mind you because I can store it during the months the plants are still young but I'd like to get some good insight. I've heard anywhere from 2-30 gallons a day during hot days. Thanks in advance for your advice!