We have a 110 foot long 10" diameter steel overflow pipe through our dam to conrol maximum water level. We need to increase our water supply and one contractor has mentioned raising the opening or intake end of the pipe.
Except for the obvious---we'd lose a few trees---what is the downside? Anyone reading this have this done?
We're not real clear about how this is done: would they add onto the existing pipe or retrench the entire length and raise the entire pipe?
Thanks for any insight.

Raising the inlet would probably be no more complicated than adding the fittings and pipe necessary to get the water side of the pipe higher. Since your pond is low right now, that would make it simpler if welding is required.

One possible negative is that you will be reducing the "head room" available to store excess water from heavy rains between the outlet pipe level and the level of the emergency spillway (or, if you didn't have one, the top of the dam). If you have a good, non-erodable spillway, this is probably not a (big) problem. If you don't have a spillway, I would put one in before reducing the headroom to greatly reduce the chance of breaching the dam.