Grand Canyon Monitoring and Research Center

Sediment Storage in the Colorado River Downstream from Glen Canyon Dam

Introduction

The sandbars exposed along the shoreline of the Colorado River represent only a small fraction of the sand deposits in Grand Canyon, most of which are on the bed of the river in eddies and the channel. Current management practice includes efforts to maintain and build sandbars by releasing high flows from Glen Canyon Dam that are timed to coincide with periods of fine-sediment supply from tributaries (High-flow Protocol Environmental Assessment). The success of this approach to build sandbars depends on the maintenance of a sufficient supply of sand within the channel. The purpose of the sediment-storage monitoring project is to track long-term trends in sand storage and thereby provide a robust measure of whether or not the supply of sand available for building sandbars is increasing, decreasing, or remaining stable over time-scales of years to decades.

Monitoring Sediment Storage

We measure changes in sediment storage by making repeat topographic maps of the river bed and banks. The maps are made by surveying exposed sediment deposits with conventional total station. These measurements involve the use of a survey instrument set on a known elevation (also called a benchmark) to measure the location and elevation of points on the ground selected by a rodman equipped with a reflective target. Most of the sediment is underwater and is measured with sonar. Multibeam sonar is the most efficient method to measure this sediment, because it is capable of mapping wide swaths of the riverbed. Singlebeam sonar measures depths directly below the instrument and is used to map areas too shallow for the multibeam equipment, but too deep for conventional survey. All of the sonar measurements are positioned by shore-based robotic total stations that track boat position in real time. GPS is not used for any of the measurements, because satellite signals are not sufficiently reliable in the deep canyon environment.
Complementary measurements of changes in sediment storage are also made by measuring sediment concentration in the water (Discharge, Sediment, and Water Quality Monitoring).



Surveying an exposed sandbar along the bank of the Colorado River in May 2014.


Boat equipped with multibeam sonar surveying the bed of the Colorado River in May 2009. Instrument in foreground is robotic total station that automatically tracks boat location and radios the position to a computer on the boat 20 times per second.
Boat equipped with singlebeam sonar for mapping the bed of the river at shallow depths along the shoreline of the Colorado River.

Recent Findings

Initial results indicate that sand storage did not decline between 2002 and 2009. This period was one of average to above average tributary sand inputs and average to below average release of water from Glen Canyon Dam. These findings are based on a period that was favorable to sand accumulation. Periods when dam release volumes are greater and tributary sediment inputs are less frequent will likely result in less sand accumulation. Recent results also demonstrate that measurements of channel change made in short reaches (less than a few miles in length) can be used to track changes in deposits and transfers of sand among the storage locations within the short reaches. The results, however, cannot be extrapolated to long segments of the river (over 10 miles in length), because the size and distribution of sand storage locations is highly variable. These findings are explained in detail in an article in the Journal of Geophysical Research and summarized in a U.S. Geological Survey Fact Sheet.


Perspective view of digital elevation model of the bed and banks of the Colorado River about 44 miles downstream from Lees Ferry, Arizona. Between 2009 and 2012, it is possible to see erosion of sediment from the bed of the river in the channel and erosion of sediment from the sandbar on the bank. The direction of streamflow is from the upper left to lower right and the river is about 450 feet wide at the widest point in this view.

Maps of the Colorado River in Grand Canyon
For Additional Information
For additional information, please contact
Project Chief
  • Paul Grams
    • USGS Southwest Biological Science Center
    • Grand Canyon Monitoring Research Center
    • Contact pgrams@usgs.gov or (928)-556-7385
Terms of Use

The data presented in this website are collected and processed using standard USGS protocols and other established peer-reviewed methods, and subject to rigorous quality control. Nevertheless, minor edits of these data are possible.

The data are released on the condition that neither the USGS nor the U.S. Government may be held liable for any damages resulting from its authorized or unauthorized use.

References
  • Grams P. E., 2013, A sand budget for Marble Canyon, Arizona--implications for long-term monitoring of sand storage change, U.S. Geological Survey Fact Sheet 2013–3074, 4 p., http://pubs.usgs.gov/fs/2013/3074/.

  • Grams, P.E., Schmidt, J.C., and Topping, D.J., 2007, The rate and pattern of bed incision and bank adjustment on the Colorado River in Glen Canyon downstream from Glen Canyon Dam, 1956-2000: Geological Society of America Bulletin, v. 119, no. 5-6, doi: 10.1130/B25969.1, p. 556-575, accessed on February 12, 2010, at http://gsabulletin.gsapubs.org/content/119/5-6/556.abstract.

  • Grams P. E., D. J. Topping, J. C. Schmidt, J. E. Hazel Jr., and M. Kaplinski (2013), Linking morphodynamic response with sediment mass balance on the Colorado River in Marble Canyon: Issues of scale, geomorphic setting, and sampling design, J. Geophys. Res. Earth Surf., 118, 361–381, doi:10.1002/jgrf.20050. http://onlinelibrary.wiley.com/doi/10.1002/jgrf.20050/full

  • Hazel, J.E., Jr., Grams, P.E., Schmidt, J.C., and Kaplinski, M., 2010, Sandbar response in Marble and Grand Canyons, Arizona, following the 2008 high-flow experiment on the Colorado River: U.S. Geological Survey Scientific Investigations Report 2010-5015, 52 p., accessed on July 27, 2010, at http://pubs.usgs.gov/sir/2010/5015/.

  • Hazel, J.E., Jr., Kaplinski, M., Parnell, R.A., Kohl, K., and Schmidt, J.C., 2008a, Monitoring fine-grained sediment in the Colorado River ecosystem, Arizona--control network and conventional survey techniques: U.S. Geological Survey Open-File Report 2008-1276, 15 p., accessed on January 27, 2010, at http://pubs.usgs.gov/of/2008/1276/.

  • Hazel, J.E., Jr., Topping, D.J., Schmidt, J.C., and Kaplinski, M., 2006b, Influence of a dam on fine-sediment storage in a canyon river: Journal of Geophysical Research, v. 111, no. F01025, doi: 10.1029/2004JF000193, p. 1-16, accessed on December 28, 2009, at http://www.agu.org/journals/jf/jf0601/2004JF000193/2004JF000193.pdf.

  • Kaplinski, M., J.E. Hazel Jr., P.E. Grams, and P.A. Davis, 2014, Monitoring Fine-Sediment Volume in the Colorado River Ecosystem, Arizona: Construction and Analysis of Digital Elevation Models, USGS Open-file Report 2014-1052, 36 p. http://pubs.usgs.gov/of/2014/1052/.

  • Wright, S.A., Schmidt, J.C., Melis, T.S., Topping, D.J., and Rubin, D.M., 2008, Is there enough sand? Evaluating the fate of Grand Canyon sandbars: Geological Society of America Today, v. 18, no. 8, doi: 10.1130/GSATG12A.1, p. 4-10, accessed on May 26, 2010, at http://www.geosociety.org/gsatoday/archive/18/8/pdf/i1052-5173-18-8-4.pdf.

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