What kind of water system should I have in Arizona for citrus trees?
Should the trench be the size of their canopy?
Certified GKH Gardening Expert
The type of water system is completely up to you and your local regulations. A simple drip line will suffice, and will cut the need for a trench as long as your planting spot has been has been prepared properly.
This collection of articles has just about everything you could need regarding irrigation, and I believe that you will find everything that you need here: https://www.gardeningknowhow.com/garden-how-to/watering