Ask any long-time river runner about the must-do Southwest rivers, and Santa Elena Canyon of the Rio Grande is likely to make the list. It may not be known for particularly challenging or high-quality whitewater, but its incredible scenery, uniqueness as an international boundary, and novelty of its very existence in this parched desert make it an iconic run.
The rapids are generally mellow, which makes the canyon accessible for all abilities and different types of craft. When high water occurs, inexperienced boaters should stay away. For most of the year, the river slides lazily through the desert at 500 cubic feet per second or less, which is perfect for canoes and kayaks. It is commonly done as a one-night trip, starting either from Lajitas and traveling downstream to Castolon, or as an out-and-back "boomerang" putting in at Castolon and paddling upstream to Rock Slide Rapid then back down.
The top-down run beginning in Lajitas tours fairly open desert for about 10 miles before entering the canyon. The scenery is beautiful, but temperatures soar well above 100 degrees in the summer, and everywhere is exposed to sun, wind, and monsoon storms. During good weather it is easy enough to escape the heat by jumping in the water, however. If you'll be doing the boomerang, you will have to contend with rapids that may require dragging your canoe to travel upstream. Winds in the canyon can be very strong, so allow some extra time in case you encounter headwinds. Calm days and good weather are common as well, just be aware of the forecast before you go and prepare appropriately.
For the most part, all rapids are straightforward read and run. The one that definitely warrants a scout is Rock Slide, which you will know by the large rockfall pile on river right and boulders choking the waterway. There are a few channels to choose from, and you should plan your line ahead of time. The moves are not extremely difficult outside of very high flows, but they are all blind turns, and you must scout to know what to expect.
Other notable rapids in the canyon are various wall shots, where the current makes sharp turns necessitated by corners in the canyon walls. These can actually be more difficult at low-medium flows because there is nowhere for the water to go but into the wall. Stay on your toes and consider scouting these when you see them coming.
While floating this remote desert river, you are also floating the boundary between the United States and Mexico. It seems like wild, boundless Chihuahuan Desert everywhere you look, but the two sides of the border have unique characteristics that you may notice between Lajitas and the Santa Elena entrance. Each side is a national park within its respective country, but they are managed differently. In Mexico, livestock and hunting are allowed, and there are some ranches within just a few miles of the river. Small towns are located within 10 miles away, and dry washes serve as avenues to access the river. You may meet ranchers or other people enjoying the desert the same way you are, simply camping out by the water. You will probably also see the cattle or feral horses that graze the banks and cross the river freely.
Campsites are not labeled or designated, but commonly used camps are not hard to pick out. The most popular site for Lajitas-Castolon overnighters is known as Entrance Camp, which is on river left just before entering Santa Elena Canyon. You should only camp on the U.S. side (river left), as river permits do not serve as authorization into Mexico. Campsites inside the canyon are generally obvious, identified as any of the relatively few wide banks in this walled-in stretch. Within the canyon, camping on either side is okay even though the river-right bank is technically Mexico.
All river trips, both day and overnight, require a permit. These must be obtained in person at any of the Big Bend National Park visitor centers or at the Barton Warnock Environmental Center near Lajitas up to 24 hours before launch. Along with the permit, all boaters must read and follow National Park Service river use regulations. If you'd rather not organize your own logistics and gear, many companies offer guided day and camping tours in Santa Elena. Search online and call various companies to find the trip right for you.