Piute Farm's waterfall is a 25-ft high cascade that has formed along the San Juan River and spans its entire width. The location is a remote spot in an upstream arm of Lake Powell reservoir.
To reach the falls it takes a rough two-hour drive from Mexican Hat, or a 100-mile-boat ride from Bullfrog Marina in Lake Powell.
It formed when the tributary re-routed itself, cut through a thick layer of sediment, and began flowing over a bedrock cliff.
Scientists call this phenomenon superimposition.
Jack Schmidt, Janet Quinney Lawson Chair of Colorado River Studies in the Quinney College of Natural Resources at USU explains, “When reservoirs are created by the construction of dams, the sediment load of inflowing rivers is deposited in the most upstream part of the reservoir. In Lake Powell...the deposits in the…San Juan arm of the reservoir are as much as 80ft thick.”
“[If} reservoirs…drop…the inflowing rivers erode into the accumulated sediment. There is no guarantee the location of the new channel will be in the same place as…the original channel.”
The San Juan River’s original route was buried under the thick layer of sediment. The river’s response was to form a new channel one mile south of the original route and over the ridge.
Schmidt continues, “A [similar] thing…happened in Lake Mead reservoir where an unrunnable rapid formed near Pearce Ferry where the new Colorado River flows over a lip… [of] consolidated sediment. Although not a vertical waterfall, Pearce Ferry Rapid is sometimes more dangerous to boating than any rapid in the Grand Canyon!”
With future droughts, we can expect reservoirs to be at low levels for extended periods, and superimposition will continue to occur forming additional waterfalls and obstructions. Managers monitor the positive and negative effects of these changes.
One impact of the Piute Farms waterfall is a novel subpopulation of endangered razorback suckers which are now blocked from swimming upstream to spawn.
Zach Ahrens, Native Aquatics Biologist at Utah Division of Wildlife Resources and graduate student at USU says, “The Razorback and other native fishes in the Colorado River basin have evolved over millions of years to play their roles in spite of the extremes of temperature and flow in their riverine environment. Given the uncertainty of future climate and water resources…it's important to do what we can to ensure their continued survival.”
Before the waterfall formed, managers were not sure what percentage of razorback suckers traveled this far upstream.
Mark McKinstry, Biological Scientist from the Bureau of Reclamation, explains, “It took perseverance, technology, and dedication of a lot of different folks to find where…the Razorbacks are and understand the fish’s life history strategy.”
Peter MacKinnon with the Quinney College of Natural Resources at Utah State University and Biomark Inc. provided the technical expertise to set up a method to insert Razorback suckers with pit tags (similar to those used in cats and dogs) then track them with antennas placed below the falls.
With this tracking method, managers and researchers identified more than 1000 razorback suckers below the falls, apparently trying to ascend the waterfall. Approximately 2000-4000 suckers live in the San Juan River. It is estimated about 25% of the Razorbacks are unable to spawn - because the waterfall blocks fish passage. This could influence the population of the endangered fish.
The Bureau of Reclamation consulted with experts on how to help razorback suckers get past the waterfall so they can move upstream and spawn. The most feasible suggestion seems to be, to build a naturalized fish passage around the side of the waterfall. Managers and volunteers would build a trap location on the upstream side of the passage where fish moving upstream could be captured; volunteers could then release the captured razorbacks and other native fish upstream where they choose to spawn.
Phaedra Budy, professor in the Watershed Sciences Department and Unit Leader for U.S. Geological Survey Cooperative Fish & Wildlife Research Unit said, “The Razorback sucker has intrinsic value to the San Juan River and beyond, is a critical member of the ecosystem, and deserves every effort for recovery.”
Managers and researchers hope their information gained and recovery efforts will give the endangered razorback suckers an increased chance for survival in its changing environment.