What is the Grand Canyon? The Grand Canyon and the region it defines includes thousands of square miles of incised canyons, mesas and volcanoes overlain by a web of drainages that feed into the Colorado River, which carved the canyon. The Colorado River in Grand Canyon National Park is 277 miles long, and the Canyon is about 18 miles wide near the south rim facilities and nearly a mile deep. It was made a national park in 1919.
Where is the Grand Canyon? In northwest Arizona, bordering Utah. The south rim of the canyon in Grand Canyon National Park is most often accessed from Hwy 180 out of Flagstaff, Arizona. The north rim is most often accessed from Hwy 89 out of southern Utah.
What is the cultural history of the Grand Canyon? Human habitation of the canyon goes back at least 10,000 years to the Clovis and Folsom cultures, who were sophisticated big-game hunters. When the climate changed to warmer and drier conditions, another culture called Desert Archaic existed from 6500 BC to 1 AD. The farming cultures, known as Basketmaker and Puebloan, inhabited the Grand Canyon until about 1275 AD. Many modern-day cultures trace their origins to the canyon, including 34 Hopi clans. The Havasupai still live in the canyon and consider themselves its guardians.
What impact has the US government had on the canyon and the Colorado River? The Bureau of Reclamation (BuRec), an agency of the US Department of the Interior, was formed in 1902 to build water projects in the West. In 1935, BuRec began filling the reservoir formed by Hoover Dam. The reservoir filled in 1941 and inundated twenty percent of the Grand Canyon. In 1963, upstream of Grand Canyon, the gates of Glen Canyon Dam were closed, initiating a potentially lethal blow to the Colorado through Grand Canyon.
How have the Colorado River dams impacted the Grand Canyon? The Grand Canyon ecosystems are collapsing because Glen Canyon Dam has prevented sediment and nutrients from flowing into the canyon, lowered the water temperature, and eliminated life-giving floods. What is sediment? Sediment comes from natural weathering processes, such as rain and ice, and is typically composed of fine clay and course sand. In natural systems, sediment is eventually transported by flowing water to the sea. The Colorado River drains an area of soft rocks and is one of the muddiest rivers in the world. The plants and animals that depend on the Colorado River evolved with this high-sediment system.
Why is sediment important? Organic materials are mixed into the sediment matrix and provide the carbon necessary for tissue growth. Organisms such as insects depend on these nutrients and provide the base for the ecosystem’s food chain. Of the 50 + species of native insects that once formed the natural food base for the Grand Canyon, none remain. The unnatural water temperature is another reason why the native insects do not reproduce. Because the Colorado River runs clear, a green alga called cladophora grows abundantly. This is an unnatural food source for native fish and has replaced the natural food web. Sediment deposits also form the Canyon’s beaches and sandbars, which in turn provide habitat for the plants, birds and mammals that evolved with this muddy river.
Doesn’t any of the sediment get through the dam? Ninety-five percent of the sediment and nutrients that once flowed through Grand Canyon’s riverine ecosystem are now trapped behind Glen Canyon Dam.
Why have water temperatures changed? Water is released through large pipes (penstocks) built into Glen Canyon Dam and turns large turbines that produce electricity. The water enters the penstocks at a depth of about 200 feet below the surface of Lake Powell, the reservoir formed by Glen Canyon Dam. Because the sun’s rays cannot penetrate water at that depth, the water is very cold. When the water exits the dam’s power plant and flows as a river once again, the temperature is about 47 ? F.
Previously, when the Colorado River flowed in its natural riverbed, water temperatures reached 80 ? F in the summer. It was these warm temperatures that triggered animal reproduction. Non-native fish, such as trout, thrive in the artificially cold water and compete with the native fish for available food. They also prey on the few native fish that manage to reproduce in the warmer waters of the Little Colorado River, a tributary of the Colorado 75 miles below Glen Canyon Dam.
Why are flood flows important? Natural flows in the Grand Canyon fluctuated seasonally from 3,000 to 90,000 cubic feet per second (cfs). A cubic foot is about eight gallons of water. Every spring the melting snows from the Rocky Mountains brought a rushing torrent of water into the Canyon. The floods moved the sediment around to form new beaches and sandbars (beaches naturally degrade due to water and wind erosion) and replenished the nutrients high on the shores of the river to be utilized by plants and animals. This process also triggered seed germination for trees such as the mesquite. Now, with dam-controlled flows, the Colorado fluctuates every day between 8,000 to 20,000 cfs, creating a near static flow regime for an ecosystem that is dependent upon a dynamic system of annual recharge.
What has happened to the native species of the Grand Canyon? River otters and muskrats are now gone from the canyon. Four of the eight native Colorado River fish are gone and two more are struggling for survival. Native vegetation is disappearing from the high water zone or is stunted due to the lack of nutrients and the invasion of competing non-native plants.
Has there been any impact on the cultural values of the Canyon? Erosion poses a threat to native burial and sacred sites near the riverbed. The loss of native species represents additional native cultural losses.
What can be done to reverse these impacts? These impacts represent a significant violation of the 1916 Organic Act (which created the National Park Service) and the Grand Canyon Protection Act of 1992. These acts require that the federal government ensure and enhance the natural integrity of Grand Canyon’s resources for future generations. This is why a growing nationwide coalition is demanding that the government obey the law and immediately:
- Restore natural sediment and nutrients flows from the Colorado into Grand Canyon
- Restore natural flow regimes to properly transport this sediment within the Canyon
- Restore the natural water temperatures of the Colorado River
What would be the initial steps for accomplishing these restoration goals? The Bureau of Reclamation and National Park Service must develop a recovery program for the Colorado River corridor in Grand Canyon that includes all species known to be native prior to the operation of Glen Canyon Dam. They need to implement a non-native eradication program to rid the Grand Canyon river corridor of alien species with a priority on those that prey on, compete with, or otherwise impair the health of native plants and animals.
How will the other restoration goals be accomplished without removing the dams? It may not be possible to save the Grand Canyon without removing Glen Canyon Dam. Over $100 million has been spent on science programs in the Grand Canyon, but no viable plan to restore the canyon has resulted. This is not due to faulty science as much as it is to the priority politics of water and power. We must initiate the necessary measures to preserve the Grand Canyon in accordance with our nation’s laws before the ecosystem collapses.
