I think the best of both worlds is a combination of excavated pond and dammed pond, in a very gentle draw or terrain that slopes about 3 feet in a hundred or so feet. With our clay soils and good runoff I think our ratio of watershed to pond is around 6:1 to 10:1. It all depends on rainfall and soils. We tend to get a lot of hard, short lasting thunderstorm rains in normal years that don't soak in much.
