It doesn't seem like we have a solid water source for this pond that would keep things filled to the desired level.
I may be wrong, but in general, 'ground water' isn't really going to push up more in some spots as opposed to others; in other words, that ground water will be at the same level for that water table. Certainly it could rise or fall with rains or lack of rain, but it's not really a spring that flows out of some hole.
If you sealed up the pond basin, you could theoretically keep it topped off with city water, but you'd still have to contend with that tree's thirst. Even if you had no roots penetrating the new pond basin, roots would eventually grow through. That's why I was asking about that tree earlier in this thread.
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