Just my two cents worth. If it was me, I would do some ground work/sealing first. Reason being is that your pond is close to empty, so that makes it like starting all over. Why fill it up now (at a monthly cost ), drain it and do work later to seal it. I agree with them above that you want a good water source, and you know now that runoff isn't enough. So I think you will need to do the pump anyway. I personally don't like the idea of needlessly losing water when you are paying for it.
Fish N chips Just so you understand the logic I used behind the decision when you are like I was (and I think Big Pond maybe also). When you have to depend on water shed it may take a very long time to fill a pond up. If you rework it first and you may even be forced into doing a water supply just to fill the pond back up. The pond is always going to be losing water thru natural means (evaporation and such) and the fact I have never seen a 100% leak proof earth dirt pond. If you can do the water supply first you may find out that the money you where going to spend for reworking will supply you water for a few decades. Also When you do get ready to rework the pond you can fill the pond alot quicker. The fact I can drain my 3 acre watershed pond and fill it in less than 3 weeks with no rain made me very happy I went water supply first.
Edit: I would have never filled up as my upland water shed coefficent dropped when the pastures where converted back into forest. I do not get near the shed I used to.
Fully agree with you on your thinking. The main point being is you have to sit down and figure out which solution is the cheapest for the duration. I probably should have said it that way. If it would cost 10,000 to seal and you can fill it for 5,000 for its duration...you got to go with the cheaper. By the sounds of it, I think the cost for the pump set-up is going to be needed no matter what. So you could take that amount out of the equation, and just deal with operating cost of pumping versus sealing cost. To me, both of these would be hard to get down exactly because of so many variables. Makes the head spin. And yes, sealing would not fix normal water losses, just major ones.
