Tailstone Rivers: What Are They and How Do They Work?

how do tailwaters transform back into freestone rivers? (fly fishing)

Foggy view of the South Boulder Creek tailwater, taken while hiking and fly fishing
Foggy view of a tailwater far downstream from the dam

April 2024

Never heard of a tailstone before? That's because we're coining the term.

When water flows downstream away from dams, tailwaters slowly evolve back into un-regulated rivers, and far enough downstream they slowly act like freestone rivers again. Over a long enough stretch, tailwaters join with tributaries, water warms, insect communities shift and the effects from any upstream dam (like water releases or storage) lessens. The resulting river is a strange mashup of tailwater sections and freestone sections, so let's explore the crossover when tailwaters act more like freestone rivers.