For any severely stressed trees, you can allow a slow running hose sit underneath the canopy for a few hours a couple of days each week until the drought breaks. This will give it enough water to keep it alive. One way to check the viability of a tree is the snap off the end of a branch or two on opposite sides of the tree to see if it is still green and pliable. If the branches are stiff and brittle, its probably at the end.
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