Somebody said upthread that the original first verse spoke of a spring, not a creek tumbling down, and that makes sense to me. Water from rare rain and snowfalls infiltrating the mesa and emerging at its base as a spring seems natural. So that's how I sang it at yesterday's singaround.

I also changed this:

The red mud walls, the waterfalls,
And the whole wide world before us;

To "canyon walls." Two reasons: if we have backed off from the town and are looking at the wide world, then the red mud walls of town have been left behind. And if there are waterfalls, we needs cliffs for them to fall off of. Said cliffs would be part of the canyons, which can be carved into the sides of the mesa.

Two: 'red mud walls' is harder to sing.