As a result, the falls can almost totally dry up in the summer with only a few narrow strips of water trickling down its face.

[2] Rainbow Falls varies widely - whether it is in full flow in the spring, or greatly diminished by the autumn.

As the flow over the falls diminishes, usually from summer to early autumn, it splits into two parts, hugging both banks.

The penstocks continue downstream past 19-ft (5m) Crooked Falls, utilizing the combined drop of over 70 ft (21m) to generate hydroelectricity through 8 turbines.

Also, water comes out of a pipe at the left bank side of the falls, and trickles into the river in a series of small waterfalls.

Meriwether Lewis was known to comment on the falls: ... hearing a tremendious roaring above me I continued ... a few hundred yards further and was again presented by one of the most bea[utiful]objects in nature, a cascade of about fifty feet perpendicular stre[t]ching at [right angles] across the river from side to side to the distance of at least a quarter of a mile.

here the river pitches over a shelving rock, with an edge as regular and streight as if formed by art, without a nich[e] or br[eak] in it; the water descends in one even and uninterrupted sheet .