Yes, we narrowed down the recharge areas and were able to track the true watersource passages in Hole in the Wall. I believe some people will be in for a surprise in the near future.
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The golf course sits over areas both on the upstream and downstream sides. The worst of the visibility, from my experience, is typically in the upstream tunnel, especially around the 600-800' penetration range. This also happens to be a section of the system that runs directly underneath the course. Other passages run under it or next to it and seepage probably doesn't occur directly down through the ground but rather will take the path of least resistance.
I use these for anything that might get much deeper than 100 feet (including flood peak) - http://www.onsetcomp.com/products/data-loggers/u22-001. There is a cheaper version that works well for shallower sites.