Periodic Spring

Most springs simply flow, but Periodic Spring pulses on a cycle, its flow rising and falling and sometimes stopping altogether before surging back. When the timing is right, a full cycle plays out over a matter of minutes, so patient visitors can watch it happen again and again.

This behavior is most pronounced when the overall flow is lower, typically in late summer and autumn. During spring runoff and high water, the spring may run more steadily and the rhythm can be hard to see, so the season matters for catching the spring at its most remarkable.

The leading explanation is that the spring is fed through a natural siphon deep in the limestone of the mountain. Water collects in a hidden chamber until it rises high enough to spill over into a looping channel, which then siphons the chamber empty in a rush, until the chamber refills and the cycle repeats.

This kind of self-emptying siphon, hidden in the soluble rock, is very rare, which is why so few rhythmic springs exist. The exact plumbing inside the mountain cannot be seen, so some mystery remains, but the siphon idea neatly explains the surge-and-pause rhythm visitors witness at the surface.

Reaching the spring is part of the experience. A gravel road climbs a canyon in the Salt River Range from near Afton, and from the road's end a trail leads up through forest along a rushing creek to the spring itself, set against the rock at the head of the walk.

The canyon is cool and green, shaded by conifers, with the creek for company, making the hike a pleasant outing in its own right. The spring emerges from the mountainside as the source of that very creek, so the water pulsing before you goes on to feed the whole canyon below.

Below the canyon lies Star Valley, a broad green farming valley along the Salt River near the Idaho border, ringed by mountains and dotted with small towns like Afton, known for its great elkhorn arch. The valley is a peaceful, scenic base for a visit.

The canyon and surrounding range hold moose, deer, elk, and mountain birds, and the forest is quiet and cool even in high summer. The road up the canyon is generally passable only in the warmer months, so the spring is a late-summer and fall destination, exactly when its rhythmic pulse is easiest to see.

The closest Boutel™ stays, so you can turn this stop into an overnight. Each is a place we chose through independent editorial review, never a paid placement.

Periodic Spring, in the mountains near the town of Afton in the Star Valley of western Wyoming, is a rare and fascinating natural wonder: a cold-water spring that flows in an on-and-off rhythm, stopping and starting on a cycle rather than running continuously. One of only a handful of such intermittent, or rhythmic, springs in the world, it gushes for a time, slows, and stops, then begins again, a behavior caused by an unusual natural siphon system underground. Set in a scenic canyon in the Bridger-Teton National Forest reached by a short hike, Periodic Spring offers a unique geologic curiosity in western Wyoming.

Periodic Spring stops and starts because of an unusual underground formation believed to act like a natural siphon: water collects in a hidden cavern until it reaches a level that triggers the siphon to drain it rapidly, causing the spring to gush, and once the cavern empties the flow stops until it fills again, repeating the cycle. This rhythmic behavior is most pronounced in the drier, lower-water times of late summer and fall, when the cycle is clearest, while high spring runoff can mask it. This rare siphoning mechanism makes Periodic Spring one of the few rhythmic springs in the world in western Wyoming.

Periodic Spring is reached by driving up a canyon road from the town of Afton into the Bridger-Teton National Forest, then taking a short hike, roughly a mile, along the trail to the spring. The walk is scenic through the canyon, and sturdy shoes are helpful, as the trail can be uneven and the area near the spring is often cool and damp. The access road is best in dry conditions and generally accessible in the warmer months. Being prepared for a short hike and mountain weather makes reaching this unique natural wonder near Afton in western Wyoming a rewarding outing.

Late summer and fall are the best times to see the periodic, on-and-off flow at its most distinct, because lower water levels let the siphoning cycle show clearly, whereas high spring snowmelt can overwhelm the rhythm and mask the effect. This period also offers pleasant hiking weather and canyon color, while the access road and trail are snowbound in winter. For the best chance to witness the spring's fascinating stop-and-start behavior along with good hiking conditions, aim for late summer or fall at Periodic Spring near Afton in western Wyoming.

Periodic Spring is in the mountains near the town of Afton in the Star Valley of western Wyoming, within the Bridger-Teton National Forest, near the Salt River Range, and within reach of the route toward Jackson Hole to the north and the town of Pinedale to the east. That makes Periodic Spring a unique natural stop to combine with Afton, the Star Valley, and the other attractions of western Wyoming on a visit to the state.