KDO-
It is difficult to give any accurate advice with what little info that you have provided.
You indicate that this is a 1/4 acre pond, but you have not indicated the depth or shape of the pond. Topography also plays an important role. What are the relative elevations of the pond, marsh, and proposed waterfall?
Based on the site configuration as I understand it, you ideally should use 2 pumps.
Post some pictures of the site. They will be a great deal of help in providing advice.
