Hello, the page discussing immersion in rivers answers most, but not all of my questions. On the page, it reads, “a natural lake that is fed by river water and springs may be used for the immersion.” The remaining question is: If a lake is formed on a river by way of building a dam in the river, is this newly formed collection of water still considered kosher for the mikveh? The river water still flows over the dam and downstream into the original river channel. There are easy beach-style entries into this body of water for easy privacy concerns.