Hi Thelka, glad to see you posting again...Kidding season must be over or did I just miss some of your posts?
You ask a tough question, partly because Permiculture is pushing the boundaries to get water where it normally does not flow/collect, and so to that endeavor you are spot on, but at the same time fighting nature for your own gain might be a battle that you cannot win. The real question is how much effort and time are you willing to invest in the building of a pond in a semi-arid location? The next question is, is there a way you can increase your chances of success to reduce the risk of wasting time and effort on a dry depression?
Dowsing might be an option. My father does this, and I have known of others, and have seen it work...though Maine is not semi-arid either.
Keen observation is another possibility, as aquifers exist all over and may be closer to the surface in certain areas then others
Wet areas can be developed easily (and by hand) to help collect water from a large area to a point of collection like a pond
Springs exist where you least expect them
I know you know all this, but a reminder may help.
Last year I was clearing
land and the guy kind of in charge of the
project was from out of state and said he wanted a "water feature" in a certain spot. That was all well and good, but it was nothing spectacular and no place I would put a pond. But that is how it goes sometimes, and so I walked the excavator in there and started building a pond. Right in the middle I hit a spring, water started bubbling up and to make a long story short, the place now has (2) ponds, and a bridge between them, rock retaining walls and is actually quite nice looking. So I ate a lot of crow on that one, but that is good. I learned water can be where you least expect it.