Good question.
Alamosa had fields with dykes that they flooded I assume from the river and they harvested them from there. I have never heard of such a thing in Durango. I agree that the Animus river is probably too fast to freeze except in unusual circumstances.
I seem to remember however that there was talk about harvesting ice from the small lake up south of Rockwood. CAn't remember the name of the lake however. It is not very large but I suppose over the space of a winter you could harvest a lot from it.
Anyone other ideas?
Frank