Question
I live in the Dallas, TX area.  The leaves on the bottom limbs of my 20 ft. tall burr oak are dying and dropping off.  The rest of the tree looks healthy.  

Strangely, this system is more pronounced when I water around the tree...but I seldom do that.

What gives?

Answer
Tim,
The Bur Oak, Quercus macrocarpa, is a very drought tolerant tree and does not like watering. I think that since the damage is only occuring when you water the tree, that you may be drowning its root system. You do not need to give this tree any extra water due to its extensive tap root and root system. Make sure that you have good drainsge in the area and that it is not prone to flooding, and this tree could live to be 200 years old.