Glen Canyon Dam and Lake Powell: The Sediment Problem
In 1969, I took the tour though Glen Canyon Dam just before putting in on a Grand Canyon trip. One of the posters in the dam’s visitor center explained that by holding back sediment carried by the Colorado River (Spanish for “red colored” river), the dam would extend the life of Hoover Dam by a hundred and fifty years. Of course, the river was green—no sediment. On the last night of that trip, August 28, we camped at Separation Canyon with three geologists from the Powell Society, exactly one hundred years after Powell had camped there, and with beer-wetted tongues applied thousands of Powell Centennial postage stamps to envelopes containing a letter celebrating Powell’s first expedition.
Glen Canyon Dam overflow in June, 1983. Photo by the author.
Glen Canyon Dam (GCD) overflowed in June, 1983, when Colorado river inflows to an already full reservoir exceeded maximum dam outflows and the Bureau of Reclamation (BOR) had to install eight-foot-high steel “boards” on the spillways to keep the lake from flowing over the dam. The resulting cavitation in the overflow tunnels caused boulders the size of cars to come flying out, and harmonic vibrations threatened the integrity of the entire dam. There were a lot of very nervous engineers.
This event, which was repeated in June, 1984, inspired Steve Hannon’s novel “Glen Canyon” (1997) about the failure of GCD. We met at one of the Glen Canyon Institute’s early meetings at Ken Sleight’s Pack Creek Ranch south of Moab. Although dam failure is rare, it is catastrophic. In the US, the worst was the 1889 failure of the South Fork Dam in PA, called the Johnstown Flood. It killed over 2,200 people after being washed out by a flash flood.[ii] Of course, neither the cost of failure nor the cost of removal is included in the cost of hydropower or irrigation; in fact it’s difficult to compare the cost of various energy sources because neither reclamation costs nor environmental costs are easily calculated. However, rest assured; your taxes will cover them.
GCD, which was started in 1063 and completed in 1966, wasn’t built for irrigation or flood control.These were provided by Hoover Dam and Lake Mead, completed in 1936 by the Bureau of Reclamation (BOR). Floods raging through the Grand Canyon weren’t a big concern to the commissioners and there wasn’t a plan to provide irrigation water to the Navajo Nation. In 1959, Luna Leopold, the chief hydrologist for the US Geological Survey (considered to be the father of modern fluvial geomorphology, also the son of Aldo Leopold, author of “Sand County Almanac,” 1949), published a report showing that the average annual discharge of the Colorado River wasn’t sufficient to keep all of the proposed reservoirs on the river full.[iii] This upended the long-held belief in the river’s volume which was based on the unusually high average annual flows used in the 1922 Colorado River Compact. But no one really cared about available water either because the amount of electricity to be produced by GCD was only 3% of the western US power supply.[iv] GCD was primarily built for two reasons: to keep the BOR’s massive staff of dam engineers busy, and to extend the life of Hoover Dam by a century and a half by retaining the heavy load of sediment that was rapidly building up in Lake Mead.2 It was supposedly built as a compromise to the proposed highly controversial Echo Park Dam in Dinosaur National Monument just downstream from the Yampa confluence, but in fact the BOR was planning to build GCD anyway. BOR built the Flaming Gorge Dam about eighty miles upstream to replace the Echo Park Dam. Both Glen Canyon and Flaming Gorge National Recreation Areas were established after the dams were built.4
Following the 1923 USGS survey of the Colorado (led by Claude Birdseye), a series of damsites were selected, including all of the sites of current dams plus a few that weren’t built.4 By the time BOR tried to get two dams in the Grand Canyon authorized (Marble and Bridge, at the time neither were in Grand Canyon National Park), whitewater boating had become popular and public resistance stopped their plans. All of the outfitters and their guides passed out or mailed flyers to clients to write their Congressional representatives to vote against the dams, and Arizona clients were encouraged to vote against the Congressmen who proposed re-authorizing the dams. I was one of the outfitters’ representatives and guides. You can still see evidence of the BOR’s test excavations in the canyon walls. Energy from these dams was destined to lift water in the Central Arizona Project canal from the Colorado to support cotton farms in Phoenix and Tuscon (now owned by Chinese companies).4 Instead, the Navajo Generating Station at Page, AZ, using coal from Black Mesa, was built. Hoover was the first really big dam, and the site was selected partly because a 1905 flood had breached a levee, diverting the river into the Salton Sea and away from the farms in Imperial Valley, California and resulting in the importation of tamarisk (salt cedar) from the Middle East to stabilize sandy river banks and levees. Of course, the tammies migrated upstream to Bluff, Utah and all the way up the mainstream and other tributaries to Colorado and Wyoming, replacing willows and cottonwoods.4
Due to climate change, reservoirs behind dams worldwide are less than half full,[v] including all of them in the Colorado drainage except Flaming Gorge on the Green north of the Uinta Mountains. Lake Powell is only forty feet above dead pool, the level at which it can no longer release water to produce electric power.[vi] McPhee Dam on the Dolores was the last large dam built in the US (1985), basically drying up the river2 , though a dam has been proposed on the lower Gunnison and pipelines have been proposed to provide water from the upper Green and Colorado to the Utah I-17 corridor and Colorado Front Range.[vii]
Humans began building dams and canals thousands of years ago in the Middle East (Tigris and Euprates), Egypt (Nile), India (Ganges) and China (Yellow) for irrigation, mostly in desert regions. We have dramatically expanded our hydraulic societies to accommodate rapidly growing populations (from about a billion globally in 1800 to about eight billion today), and since 1882 have been building hydroelectric dams.[viii]
Before the level of Lake Powell began to decline in 2000, about two million people visited it annually, and nearly thirty thousand people floated the nicely controlled flow of the river through Grand Canyon annually. These folks benefit from Glen Canyon Dam. However, there are some who are quite upset. In 1979, Jim Styles published a cartoon in The Canyon Zephyr (Moab, UT) showing a destroyed GCD. Styles was a friend of Ed Abbey, author of the “Monkey Wrench Gang,” a 1975 novel in which four characters sabotage the coal railway from Black Mesa to Page, among other ecoterrorist activities. Some people think Abbey’s book inspired Earth First!, a radical environmental group. The book certainly made Katie Lee happy – listen to her song “Pore Colly Raddy” on YouTube. She likes to refer to the dam builders as the Bureau of WreckTheNation and Lake Powell as Lake Foul. She floated Glen Canyon and Grand Canyon with Mexican Hat Expeditions in the 1940s and 50s, but after GCD was built she refused to float Grand Canyon (personal communication). According to Dan Shultz’ book “Dead Run” (2014), Abbey may have also have inspired the three men who killed a deputy in Cortez and tried to escape down the San Juan to their bomb stash. The Sierra Club published “The Place No One Knew” in 1963, when the gates of GCD first closed, as a memorial to Glen Canyon. David Brower, the Executive Director at the time, thought flooding Glen Canyon was like flooding the Sistine Chapel – a sacrilege.[ix]
Museum of Northern Arizona Ecologic Survey raft stuck on a rock in Hance Rapids at about 2000 cubic feet per second (cfs) in January, 1974, about the amount of dam leakage and side canyon discharge when the generators are shut down (or dead pool). This discharge is suitable for kayak and inflatable kayak trips. Commercial oar trips need at least 5000 cfs, and commercial motor trips need at least 10,000 cfs. Photo by the author.
So, what’s the future? No way the BOR will destroy the dam and flood Lake Mead with sediment, though the Glen Canyon Institute is pushing plans to Fill Mead First, and how do we get water past the dam after it reaches dead pool?6 Side canyons are already recovering, but it will take a century or more for the bathtub ring to fade. Paddle a canoe through the collapsing sand cliffs along the emerging river? Use amphibious vehicles on what’s left of the lake? What about boating the Grand Canyon?
Peter Winn is a retired geologist, river outfitter and river guide with global experience. He began teaching rafting skills to new Grand Canyon river guides on the San Juan in the early 1970s, fell in love with the Bluff area and decided to retire here in 2015.
 Personal communication.
[iii] “Probability Analysis Applied to a Water-Supply Problem” by Luna Leopold (1959), Geological Survey Circular 410.
[iv] “Dead Pool” by James Lawrence Powell (2011), at the Bluff Library, and “A View of the River” by Luna Leopold (1996)
[vi] https://www.glencanyon.org/wp-content/uploads/2022/08/Final-Antique-Plumbing-at-Glen- Canyon-Dam.pdf and especially https://qcnr.usu.edu/coloradoriver/files/CCRS_White_Paper_1.pdf (about the sediment problem)
[viii] “The Hydraulic State: Science and Society in the Ancient World” by Charles R. Ortloff (2020)
[ix] “Conversations with the Archdruid” by John McPhee (1971)