[Salmo Nella]

In a previous post, bigcliff talked about having your fly float naturally without being drug through the water by the fly line. "mending" the line involves re-positioning the fly line on the water (after the cast usually) in order to keep the line from putting drag on the fly so that it can float naturally for longer. There are lots of techniques for mending in different situations. Some lines are easier to mend than others because of their taper or how well they float. Mending is not easy to do well. Doug M. may be able to describe it in words but I will not even try.

Tailwaters refer to rivers that exit below dams. They typically have a different ecology than an open water river (undammed) in the same area.

Both good questions, by the way.
Keep em coming.