Google 'chandler,az' they have a watering schedule that out lines everything.

Be sure to check and see how deeply your tree was planted. The soil from the container should be level with the surrounding soil. Planting too deeply restricts the oxygen to the trunk tissue basically suffocating the tree. Gently remove soil near the trunk until you can see the trunk flare or region where trunk tissue becomes root tissue. You may even see the tops of the roots. If this is the case remove about a 12 inch area of soil around the trunk just deep enough so the roots are barely covered with soil.

As far as watering your mesquite, as long as you are watering deeply (to a depth of three feet) you shouldn't need to water any more often than once every 10 days or so in the summer. Extend the interval as the weather cools and by winter water once every three or four weeks. Assuming your tree has a canopy diameter of six feet, apply about 20 gallons each time.

Here is the link to watering guidelines on the City of Chandler web site.

Here is a link that might be useful: Landscape Watering Guidelines