High-Flow Experiments on the Colorado River Active
Glen Canyon Dam has altered flow and fine sediment (sand, silt, and clay) dynamics of the Colorado River in Grand Canyon. Before the dam, the Colorado River experienced highly variable flows and carried a large amount of sediment through Grand Canyon, which maintained sandbars (highly valued camping areas in Grand Canyon) and provided sand that protected archeological and cultural sites from damaging erosion. Since completion of the dam in 1963, relatively little sediment is carried into Grand Canyon. This, coupled with an increase in average daily flows and daily flow fluctuations for power generation have caused sandbar erosion. To manage limited sand resources in Grand Canyon, experimental high flows, which are much higher than base-operations flows, are periodically conducted. High-flow experiments are designed to determine if limited sediment resources can be managed to maintain or increase sandbar size. The Grand Canyon Monitoring and Research Center, part of the Southwest Biological Science Center, conducts monitoring and research studies of these experimental flows.
Background
The Colorado River is one of the longest rivers in the United States with its origins in the Rocky Mountains of the western United States. Historically, the river flowed into the Gulf of California; however, due to the network of dams and water diversions constructed on the Colorado River and its tributaries, it now rarely reaches the gulf. One of those dams is Glen Canyon Dam which is located near Page, Arizona. Glen Canyon Dam construction was completed in 1963 and Lake Powell, the reservoir created by the dam, took about 17 years to completely fill. The dam and reservoir serve several purposes including water storage, flood control, generating hydroelectric power, and providing recreational opportunities. Glen Canyon Dam has altered the dynamics of the Colorado River in Grand Canyon, including the variables that influence sandbars—river flow and fine sediment (sand, silt, and clay) supply and transport. To address this, high-flow experiments are periodically conducted.
A high-flow experiment is a release of water from Glen Canyon Dam that is much larger than the base flow that is normally released. This type of experimental flow is conducted specifically to mobilize sand from the bottom of the Colorado River to rebuild sandbars and beaches in Grand Canyon, and they generally last for several days. An additional, and important function of this type of experiment is to provide opportunities to study sandbar development in the Colorado River and sand movement in the river and surrounding landscape within Glen Canyon (directly downstream of Glen Canyon Dam and part of Glen Canyon National Recreation Area) and Grand Canyon (including in Grand Canyon National Park). The information gained from these experiments provide Grand Canyon National Park managers the information they need to make appropriate decisions about the park’s resources. The Grand Canyon Monitoring and Research Center, part of the Southwest Biological Science Center, conducts much of the science associated with high-flow experiments and its scientists are experts in river-based and land-based sediment movement.
Why are High-Flow Experiments Done? The Colorado River in Grand Canyon Before and After Glen Canyon Dam.
Glen Canyon Dam has influenced many aspects of the Colorado River; however, the changes to the river’s sand dynamics are the primary reason for conducting high-flow experiments. Before the dam was constructed, the Colorado River would transport large amounts of fine sediment downstream through Grand Canyon. Some would be deposited on the bed of the river, and during floods, sand would be deposited on sandbars and beaches on the margins of the river above levels of base flow. Most of that sediment now accumulates in Lake Powell instead of being transported downstream. The Colorado River downstream of the dam now transports less than 5-20% of the sand it historically transported. Most of sand inputs now come from the Paria River, approximately 17 river miles downstream of Glen Canyon Dam, and the Little Colorado River, approximately 75 miles downstream of the dam. Both tributaries only contribute significant amounts of sediment to the Colorado River during large precipitation events.
In addition to limiting sand supply, Glen Canyon Dam has dramatically altered the flow of the Colorado River. Before the dam, the Colorado River experienced large spring snowmelt floods that were commonly 71,000 cubic feet per second (about 530,000 gallons per second) or larger, with the largest flood on record reaching approximately 210,000 cubic feet per second (about 1,571,000 gallons per second) in June 1884. During other parts of the year, the flows could be very low with the lowest flow recorded at 1,095 cubic feet per second (about 8,200 gallons per second) in August 1934. Now, daily flows of the Colorado River are largely determined by hydroelectric power generation needs and varies between about 8,000-17,000 cubic feet per second (about 60,000-127,000 gallons per second) depending on the time of day, month, and season. Therefore, before Glen Canyon Dam, the Colorado River experienced much higher flood flows and much lower base flows than it does today, and these changes have influenced sand dynamics in Grand Canyon.
In addition to transporting and depositing large amounts of sand, Colorado River floods prior to Glen Canyon Dam would strip vegetation off sandbars. During low flow periods, much of the sand deposited on sandbars and on the channel bottom became exposed. Wind would transport sand from those areas to sand dune fields. Many sand dune fields in Grand Canyon contain or are near important archaeological and cultural sites. Sand can provide protective cover to these sites which are otherwise prone to natural gully erosion processes caused by runoff during intense rainstorms that are common during the annual late-summer monsoon season in Grand Canyon.
The regulated flows of the modern-day Colorado River in Grand Canyon, combined with the greatly diminished sand supply, are not favorable for building or maintaining sandbars. Therefore, without high-flow events sandbars are slowly decreasing in size due to erosion. In addition, regulated flows of the modern river have caused dense stands of vegetation to encroach onto bare sand surfaces, decreasing the amount of area available for campsites in Grand Canyon. Approximately 25,000 recreationists per year travel through Grand Canyon on the Colorado River or hike to the river, and sandbar campsites are an important part of that experience. Additionally, the expansion of riparian vegetation onto otherwise bare sand limits the amount of sand that can be blown from sandbars onto sand dune fields and fill erosional gullies. This has allowed some erosional processes to negatively affect archaeological sites and many of these sites are in danger of being damaged or lost.
High-Flow Experiments
High-flow experiments are conducted when enough sediment from tributaries has been deposited on the bed of the Colorado River such that sand can be mobilized to increase the size of sandbars along the margin of the river in Grand Canyon without transporting out more sand than was present prior to the tributary inputs. This occurs by allowing much larger volumes of water through Glen Canyon Dam for a few days, which transports sand from the river channel to sandbars and beaches. High-flow experiments result in water flows much higher than the typical base-operations flows from Glen Canyon Dam, with between 31,500-45,000 cubic feet per second (about 236,000-337,000 gallons per second) released during the experiments. Although these flows are approximately half the magnitude and a fraction of the duration of the average spring snowmelt floods that occurred prior to Glen Canyon Dam, high-flow experiments can increase the size of sandbars in Grand Canyon. However, because the river’s modern-day flows erode sandbars over time, it is necessary to repeat high-flow experiments to maintain sandbars that erode during base operations. Monitoring results also suggest that there are cumulative effects of sand resupply to dune fields when annual high-flow experiments are conducted consistently in consecutive years. High-flow experiments have been conducted in 1996, 2004, 2008, 2012, 2013, 2014, 2016, and 2018 (November 5-8). Grand Canyon Monitoring and Research Center scientists continue to monitor the effects of these high-flow experiments and provide that information to resource managers and decision makers so they can make informed decisions about managing the resources of Grand Canyon.
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Effects of three high-flow experiments on the Colorado River ecosystem downstream from Glen Canyon Dam, Arizona
Three experimental high-flow releases from Glen Canyon Dam, Arizona— Effects on the downstream Colorado River ecosystem
Flow structures and sandbar dynamics in a canyon river during a controlled flood, Colorado River, Arizona
Effects of the 2008 high-flow experiment on water quality in Lake Powell and Glen Canyon Dam releases, Utah-Arizona
Proceedings of the Colorado River Basin Science and Resource Management Symposium, November 18-20, 2008, Scottsdale, Arizona
Sediment-transport during three controlled-flood experiments on the Colorado River downstream from Glen Canyon Dam, with implications for eddy-sandbar deposition in Grand Canyon National Park
Grain-size evolution in suspended sediment and deposits from the 2004 and 2008 controlled-flood experiments in Marble and Grand Canyons, Arizona
Basal Resources in Backwaters of the Colorado River Below Glen Canyon Dam-Effects of Discharge Regimes and Comparison with Mainstem Depositional Environments
2008 High-flow experiment at Glen Canyon Dam: Morphologic response of eddy-deposited sandbars and associated aquatic backwater habitats along the Colorado River in Grand Canyon National Park
Short-Term Effects of the 2008 High-Flow Experiment on Macroinvertebrates in Colorado River Below Glen Canyon Dam, Arizona
Effects of High-Flow Experiments from Glen Canyon Dam on Abundance, Growth, and Survival Rates of Early Life Stages of Rainbow Trout in the Lees Ferry Reach of the Colorado River
Sandbar response in Marble and Grand Canyons, Arizona, following the 2008 high-flow experiment on the Colorado River
Below are data or web applications associated with this project.
Below are partners associated with this project.
- Overview
Glen Canyon Dam has altered flow and fine sediment (sand, silt, and clay) dynamics of the Colorado River in Grand Canyon. Before the dam, the Colorado River experienced highly variable flows and carried a large amount of sediment through Grand Canyon, which maintained sandbars (highly valued camping areas in Grand Canyon) and provided sand that protected archeological and cultural sites from damaging erosion. Since completion of the dam in 1963, relatively little sediment is carried into Grand Canyon. This, coupled with an increase in average daily flows and daily flow fluctuations for power generation have caused sandbar erosion. To manage limited sand resources in Grand Canyon, experimental high flows, which are much higher than base-operations flows, are periodically conducted. High-flow experiments are designed to determine if limited sediment resources can be managed to maintain or increase sandbar size. The Grand Canyon Monitoring and Research Center, part of the Southwest Biological Science Center, conducts monitoring and research studies of these experimental flows.
Background
The Colorado River is one of the longest rivers in the United States with its origins in the Rocky Mountains of the western United States. Historically, the river flowed into the Gulf of California; however, due to the network of dams and water diversions constructed on the Colorado River and its tributaries, it now rarely reaches the gulf. One of those dams is Glen Canyon Dam which is located near Page, Arizona. Glen Canyon Dam construction was completed in 1963 and Lake Powell, the reservoir created by the dam, took about 17 years to completely fill. The dam and reservoir serve several purposes including water storage, flood control, generating hydroelectric power, and providing recreational opportunities. Glen Canyon Dam has altered the dynamics of the Colorado River in Grand Canyon, including the variables that influence sandbars—river flow and fine sediment (sand, silt, and clay) supply and transport. To address this, high-flow experiments are periodically conducted.
A high-flow experiment is a release of water from Glen Canyon Dam that is much larger than the base flow that is normally released. This type of experimental flow is conducted specifically to mobilize sand from the bottom of the Colorado River to rebuild sandbars and beaches in Grand Canyon, and they generally last for several days. An additional, and important function of this type of experiment is to provide opportunities to study sandbar development in the Colorado River and sand movement in the river and surrounding landscape within Glen Canyon (directly downstream of Glen Canyon Dam and part of Glen Canyon National Recreation Area) and Grand Canyon (including in Grand Canyon National Park). The information gained from these experiments provide Grand Canyon National Park managers the information they need to make appropriate decisions about the park’s resources. The Grand Canyon Monitoring and Research Center, part of the Southwest Biological Science Center, conducts much of the science associated with high-flow experiments and its scientists are experts in river-based and land-based sediment movement.
Why are High-Flow Experiments Done? The Colorado River in Grand Canyon Before and After Glen Canyon Dam.
Glen Canyon Dam has influenced many aspects of the Colorado River; however, the changes to the river’s sand dynamics are the primary reason for conducting high-flow experiments. Before the dam was constructed, the Colorado River would transport large amounts of fine sediment downstream through Grand Canyon. Some would be deposited on the bed of the river, and during floods, sand would be deposited on sandbars and beaches on the margins of the river above levels of base flow. Most of that sediment now accumulates in Lake Powell instead of being transported downstream. The Colorado River downstream of the dam now transports less than 5-20% of the sand it historically transported. Most of sand inputs now come from the Paria River, approximately 17 river miles downstream of Glen Canyon Dam, and the Little Colorado River, approximately 75 miles downstream of the dam. Both tributaries only contribute significant amounts of sediment to the Colorado River during large precipitation events.
In addition to limiting sand supply, Glen Canyon Dam has dramatically altered the flow of the Colorado River. Before the dam, the Colorado River experienced large spring snowmelt floods that were commonly 71,000 cubic feet per second (about 530,000 gallons per second) or larger, with the largest flood on record reaching approximately 210,000 cubic feet per second (about 1,571,000 gallons per second) in June 1884. During other parts of the year, the flows could be very low with the lowest flow recorded at 1,095 cubic feet per second (about 8,200 gallons per second) in August 1934. Now, daily flows of the Colorado River are largely determined by hydroelectric power generation needs and varies between about 8,000-17,000 cubic feet per second (about 60,000-127,000 gallons per second) depending on the time of day, month, and season. Therefore, before Glen Canyon Dam, the Colorado River experienced much higher flood flows and much lower base flows than it does today, and these changes have influenced sand dynamics in Grand Canyon.
In addition to transporting and depositing large amounts of sand, Colorado River floods prior to Glen Canyon Dam would strip vegetation off sandbars. During low flow periods, much of the sand deposited on sandbars and on the channel bottom became exposed. Wind would transport sand from those areas to sand dune fields. Many sand dune fields in Grand Canyon contain or are near important archaeological and cultural sites. Sand can provide protective cover to these sites which are otherwise prone to natural gully erosion processes caused by runoff during intense rainstorms that are common during the annual late-summer monsoon season in Grand Canyon.
The regulated flows of the modern-day Colorado River in Grand Canyon, combined with the greatly diminished sand supply, are not favorable for building or maintaining sandbars. Therefore, without high-flow events sandbars are slowly decreasing in size due to erosion. In addition, regulated flows of the modern river have caused dense stands of vegetation to encroach onto bare sand surfaces, decreasing the amount of area available for campsites in Grand Canyon. Approximately 25,000 recreationists per year travel through Grand Canyon on the Colorado River or hike to the river, and sandbar campsites are an important part of that experience. Additionally, the expansion of riparian vegetation onto otherwise bare sand limits the amount of sand that can be blown from sandbars onto sand dune fields and fill erosional gullies. This has allowed some erosional processes to negatively affect archaeological sites and many of these sites are in danger of being damaged or lost.
High-Flow Experiments
High-flow experiments are conducted when enough sediment from tributaries has been deposited on the bed of the Colorado River such that sand can be mobilized to increase the size of sandbars along the margin of the river in Grand Canyon without transporting out more sand than was present prior to the tributary inputs. This occurs by allowing much larger volumes of water through Glen Canyon Dam for a few days, which transports sand from the river channel to sandbars and beaches. High-flow experiments result in water flows much higher than the typical base-operations flows from Glen Canyon Dam, with between 31,500-45,000 cubic feet per second (about 236,000-337,000 gallons per second) released during the experiments. Although these flows are approximately half the magnitude and a fraction of the duration of the average spring snowmelt floods that occurred prior to Glen Canyon Dam, high-flow experiments can increase the size of sandbars in Grand Canyon. However, because the river’s modern-day flows erode sandbars over time, it is necessary to repeat high-flow experiments to maintain sandbars that erode during base operations. Monitoring results also suggest that there are cumulative effects of sand resupply to dune fields when annual high-flow experiments are conducted consistently in consecutive years. High-flow experiments have been conducted in 1996, 2004, 2008, 2012, 2013, 2014, 2016, and 2018 (November 5-8). Grand Canyon Monitoring and Research Center scientists continue to monitor the effects of these high-flow experiments and provide that information to resource managers and decision makers so they can make informed decisions about managing the resources of Grand Canyon.
- Science
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Below are publications associated with this project.
Filter Total Items: 30Effects of three high-flow experiments on the Colorado River ecosystem downstream from Glen Canyon Dam, Arizona
Three high-flow experiments (HFEs) were conducted by the U.S. Department of the Interior at Glen Canyon Dam, Arizona, in March 1996, November 2004, and March 2008. These experiments, also known as artificial or controlled floods, were large-volume, scheduled releases of water from Glen Canyon Dam that were designed to mimic some aspects of pre-dam Colorado River seasonal flooding. The goal of thesAuthorsTheodore S. MelisThree experimental high-flow releases from Glen Canyon Dam, Arizona— Effects on the downstream Colorado River ecosystem
Three high-flow experiments (HFEs) were conducted by the U.S. Department of the Interior at Glen Canyon Dam, Arizona, in March 1996, November 2004, and March 2008. Also known as artificial or controlled floods, these scheduled releases of water above the dam's powerplant capacity were designed to mimic pre-dam seasonal flooding on the Colorado River. The goal of the HFEs was to determine whether hAuthorsTheodore S. Melis, Paul E. Grams, Theodore A. Kennedy, Barbara E. Ralston, Christopher T. Robinson, John C. Schmidt, Lara M. Schmit, Richard A. Valdez, Scott A. WrightFlow structures and sandbar dynamics in a canyon river during a controlled flood, Colorado River, Arizona
In canyon rivers, debris fan constrictions create rapids and downstream pools characterized by secondary flow structures that are closely linked to channel morphology. In this paper we describe detailed measurements of the three‐dimensional flow structure and sandbar dynamics of two pools along the Colorado River in the Grand Canyon during a controlled flood release from Glen Canyon Dam. Results iAuthorsScott A. Wright, M. KaplinskiEffects of the 2008 high-flow experiment on water quality in Lake Powell and Glen Canyon Dam releases, Utah-Arizona
Under the direction of the Secretary of the Interior, the U.S. Geological Survey`s Grand Canyon Monitoring and Research Center (GCMRC) conducted a high-flow experiment (HFE) at Glen Canyon Dam (GCD) from March 4 through March 9, 2008. This experiment was conducted under enriched sediment conditions in the Colorado River within Grand Canyon and was designed to rebuild sandbars, aid endangered humpbAuthorsWilliam S. VernieuProceedings of the Colorado River Basin Science and Resource Management Symposium, November 18-20, 2008, Scottsdale, Arizona
Since the 1980s, four major science and restoration programs have been developed for the Colorado River Basin to address primarily the conservation of native fish and other wildlife pursuant to the Endangered Species Act (ESA): (1) Recovery Implementation Program for Endangered Fish Species in the Upper Colorado River Basin (commonly called the Upper Colorado River Endangered Fish Recovery ProgramAuthorsTheodore S. Melis, John F. Hamill, Glenn E. Bennett, Lewis G. Coggins,, Paul E. Grams, Theodore A. Kennedy, Dennis M. Kubly, Barbara E. RalstonSediment-transport during three controlled-flood experiments on the Colorado River downstream from Glen Canyon Dam, with implications for eddy-sandbar deposition in Grand Canyon National Park
Three large-scale field experiments were conducted on the Colorado River downstream from Glen Canyon Dam in 1996, 2004, and 2008 to evaluate whether artificial (that is, controlled) floods released from the dam could be used in conjunction with the sand supplied by downstream tributaries to rebuild and sustainably maintain eddy sandbars in the river in Grand Canyon National Park. Higher suspended-AuthorsDavid J. Topping, David M. Rubin, Paul E. Grams, Ronald E. Griffiths, Thomas A. Sabol, Nicholas Voichick, Robert B. Tusso, Karen M. Vanaman, Richard R. McDonaldGrain-size evolution in suspended sediment and deposits from the 2004 and 2008 controlled-flood experiments in Marble and Grand Canyons, Arizona
Since the closure of Glen Canyon Dam in 1963, the hydrology, sediment supply, and distribution and size of modern alluvial deposits in the Colorado River through Grand Canyon have changed substantially (e.g., Howard and Dolan, 1981; Johnson and Carothers, 1987; Webb et al., 1999; Rubin et al., 2002; Topping et al., 2000, 2003; Wright et al., 2005; Hazel et al., 2006). The dam has reduced the fluviAuthorsAmy E. Draut, David J. Topping, David M. Rubin, Scott A. Wright, John C. SchmidtBasal Resources in Backwaters of the Colorado River Below Glen Canyon Dam-Effects of Discharge Regimes and Comparison with Mainstem Depositional Environments
Eight species of fish were native to the Colorado River before the closure of Glen Canyon Dam, but only four of these native species are currently present. A variety of factors are responsible for the loss of native fish species and the limited distribution and abundance of those that remain. These factors include cold and constant water temperatures, predation and competition with nonnative fishAuthorsKatherine E. Behn, Theodore A. Kennedy, Robert O. Hall2008 High-flow experiment at Glen Canyon Dam: Morphologic response of eddy-deposited sandbars and associated aquatic backwater habitats along the Colorado River in Grand Canyon National Park
The March 2008 high-flow experiment (HFE) at Glen Canyon Dam resulted in sandbar deposition and sandbar reshaping such that the area and volume of associated backwater aquatic habitat in Grand Canyon National Park was greater following the HFE. Analysis of backwater habitat area and volume for 116 locations at 86 study sites, comparing one month before and one month after the HFE, shows that totalAuthorsPaul E. Grams, John C. Schmidt, Matthew E. AndersenShort-Term Effects of the 2008 High-Flow Experiment on Macroinvertebrates in Colorado River Below Glen Canyon Dam, Arizona
Glen Canyon Dam has dramatically altered the physical environment (especially discharge regime, water temperatures, and sediment inputs) of the Colorado River. High-flow experiments (HFE) that mimic one aspect of the natural hydrograph (floods) were implemented in 1996, 2004, and 2008. The primary goal of these experiments was to increase the size and total area of sandbar habitats that provide boAuthorsEmma J. Rosi-Marshall, Theodore A. Kennedy, Dustin W. Kincaid, Wyatt F. Cross, Holly A.W. Kelly, Kathrine A. Behn, Tyler White, Robert O. Hall, Colden V. BaxterEffects of High-Flow Experiments from Glen Canyon Dam on Abundance, Growth, and Survival Rates of Early Life Stages of Rainbow Trout in the Lees Ferry Reach of the Colorado River
High-flow experiments (HFEs) from Glen Canyon Dam are primarily intended to conserve fine sediment and improve habitat conditions for native fish in the Colorado River as it flows through Grand Canyon National Park, Arizona. These experimental flows also have the potential to affect the rainbow trout (Oncorhynchus mykiss) population in the Lees Ferry tailwater reach immediately below the dam, whicAuthorsJosh Korman, Matthew Kaplinski, Theodore S. MelisSandbar response in Marble and Grand Canyons, Arizona, following the 2008 high-flow experiment on the Colorado River
A 60-hour release of water at 1,203 cubic meters per second (m3/s) from Glen Canyon Dam in March 2008 provided an opportunity to analyze channel-margin response at discharge levels above the normal, diurnally fluctuating releases for hydropower plant operations. We compare measurements at sandbars and associated campsites along the mainstem Colorado River, downstream from Glen Canyon Dam, at 57 loAuthorsJoseph E. Hazel, Paul E. Grams, John C. Schmidt, Matt Kaplinski - Web Tools
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