Evolution of the Watershed
An important idea to remember is that watersheds change over time. The course of a stream becomes more serpentine, the types of trees surrounding the stream cycle in their own circle. Most often these changes take place too slowly for us to appreciate, but they still occur.
Other natural changes occur at a much faster rate, such as beaver dams. Beavers are part of Pennsylvania's natural wildlife and play their own part in watershed evolution. A dam may cause a lake to form where a stream used to cut through a forest, eventually this lake will drain some and collect sediment to become wetlands. It may even turn into a meadow and later germinate the forest that was once there. As with all disturbances, the first change happens quickly with the building of the dam and flooding to form a lake. the subsequent restoration to a forest takes many years.
Even though many of the techniques we use today are designed to be
essentially hands-off, monitoring will still be necessary. We may not
see evolutionary changes in a month or 2, but in 20 years there may be
differences in the watershed that the next generation will have to adapt to.