Ok... if you are going to fill a so-called 'well' with water brought from a river, wouldn't you call that a cistern instead?
A cistern would be much more appropriate than a well, in this setting, as you could use it to collect rain-water or be filled by buckets of water brought from a nearby river.
Until mining is released, a groundwater well would just seem odd (in light of the groundwater level argument). However, a cistern would be not only understandable, but acceptable as well because it can be a completely above-ground building that would merely hold water that could be brought in from a remote source.
The availability of a cistern would also allow tribes to have their lands far from any constant water source (which is quite possible, since I've scouted enough areas to know that there are great places to settle, if only there was a source of water).
For more information on the history of the cistern and reasons why it would be best applied to Xsyon, instead of a well, see the following Wikipedia entry.
http://en.wikipedia.org/wiki/Cistern
If you took the time to read my 'essay' and agree with my idea, please PM me about it. Thank you for your time.