Q.How often should I water my crepe myrtle?
How wide should make the base on the ground to hold the water? I transplanted a medium sized tree last year in Feb. when it had no leaves. It sprouted all new leaves but never really grew. Now all the leaves are brown and it appears to be dying. How do I know it is still alive?

Certified GKH Gardening Expert
You can tell if it is still alive by breaking off the tip of a branch and looking for green inside. Or just scrape off the outside layer of a stem and look for green inside.
It may have been planted too deeply during the move. Crape myrtles usually decline if they are not planted level with the nursery container, or in your case, the same height it was in the ground.
https://www.gardeningknowhow.com/ornamental/trees/crepe-myrtle/crepe-myrtle-tree-problems.htm