Pumping from the creek isn't unusual in arid areas. The only problem is getting unexpected fish out of the creek. I have no idea how they survive the impeller but they do.
If I were going to drain it, I would use a siphon. There are several references here and instructions. Don't break the dam.
However, if the proximity to the creek is the problem, I would think that you have some sort of sand type aquifer between the creek and the pond. You would have to identify and solve that problem. 1" per day doesn't sound bad in my part of the world. If it were me, and it's not, I would probably go for the bandaid approach and filter the creek output.
