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LR Letter
January 14, 2002

To GCNRA/BuRec: Sediment management for Lake Powell reservoir

Superintendent Kitty Roberts
Glen Canyon National Recreation Area
P.O. Box 1507
691 Scenic View Road
Page, AZ 86040-1507

Re: Development Concept Plan (DCP) for Hite Marina and Sediment Management Plan for Glen Canyon National Recreation Area (GCNRA)

Dear Ms. Roberts:

Living Rivers and the eight undersigned groups submit the following comments pertaining to the DCP at Hite Marina. Our concerns with the proposed Plan are threefold.

1) The Plan must give sufficient consideration to impacts of sediment on the continued operations and future development in and around Hite Marina.

2) Because sediment accumulation is a growing concern, not only at Hite Marina but elsewhere on the reservoir, and at Glen Canyon Dam, GCNRA, in conjunction with other management agencies, should first complete a comprehensive sediment management plan for the reservoir. Such a study must assess the operational life span of GCNRA's reservoir activities as dictated by sediment impacts on the operation of Glen Canyon Dam.

3) The prioritization by GCNRA to move forward on the Hite Marina DCP demonstrates a bias toward further accommodation of one form of recreation, namely those employing motorized reservoir watercraft, while continuing to ignore the concerns being raised by those utilizing GCNRA river corridors.


It is encouraging that the outline for the DCP makes reference to sediment mitigation at Hite Marina. For this to be properly addressed GCNRA must first ensure that all potential inflows, not just the Colorado's main stem but the Dirty Devil, Escalante, and San Juan rivers, are evaluated. This includes the numerous, ephemeral side-canyons of the reservoir too. It is also critical that GCNRA work with the Bureau of Reclamation (BuRec) to incorporate potential changes in dam operations that will affect sediment mobilization and the impacts they will have at Hite Bay. This should include dam operations affected by climate, as well as those associated with other management plans such as the Interim Surplus Criteria (ISC).

Sediment mitigation is not solely an issue at Hite Marina, but an unavoidable problem throughout the NRA. Sediment in Lake Powell reservoir was anticipated when Glen Canyon Dam was built and when the NRA became operational. Now that sediment impacts are becoming more commonplace, it's critical that GCNRA coordinate with other agencies within the Department the Interior (DOI) to prepare a comprehensive Sediment Management Plan and associated EIS for its implementation. This must be completed prior to any further work on the Hite Marina DCP, as its findings will directly inform development options for the area.

In the past, concerns with regard to sediment management have been raised by Living Rivers and others in the context of impaired access for river users at GCNRA, especially along the San Juan arm. Although staff from GCNRA has participated in several meetings, GCNRA has made no commitment to address this matter of growing public safety, health and access. GCNRA, however, is investing significant resources in moving forward on the DCP for Hite Marina, principally to benefit motorized recreation on Lake Powell reservoir. GCNRA should be working to ensure maintaining access for all existing users first. It should not be investing in expansion plans for one group of users, while ignoring those issues that are impeding access for others. Work on the DCP for Hite Marina should be suspended until GCNRA has mitigated the sediment problem along the San Juan arm of the reservoir.


The construction of Glen Canyon Dam began in 1957 and the impoundment of Colorado River water at Glen Canyon began in 1963. The reservoir reached an appropriate elevation to generate electricity in 1964. The Bureau of Reclamation (BuRec) manages the operation of the dam, power plant and reservoir. In 1972 Congress created GCNRA to manage the recreation and natural resources in the Glen Canyon region, including Rainbow Bridge National Monument. The Navajo Nation manages the resources south of the San Juan River and the Corps of Engineers regulates the waterways (Section 404 of the Clean Water Act).

The Colorado River is famous for its suspended sediment load. In 1925 testimony was presented before a Senate committee stating that the "Colorado has a silt content three times that of the Ganges and ten times that of the Nile. With the possible exception of the Tigris, it is the greatest silt-bearing stream in the world (The Boulder Canyon Project by Paul L. Kleinsorge)." This quantity of sediment is one of the two reasons why Hoover Dam was built. The other was to store water for consumptive use by agriculture interests downstream.

According to the Weymouth Report of 1929 (Senate Document #186, 70th Congress), the total suspended sediment load for Lake Mead reservoir created by the Boulder Canyon Project would amount to 137,000 acre-feet per year. Weymouth predicted that a sediment plug would ultimately form before the dam face that would compromise the dam's generator penstocks after 50 years (1985) of impounding the Colorado River. Such sediment mitigation has now been pre-empted and transferred upstream to Glen Canyon Dam.

A report published in 1961 by Ernest R. Schultz of BuRec titled Design Features of Glen Canyon, states that sediment mitigation at Glen Canyon Dam would need to be underway within 100 years of impoundment (2063), as sediment levels would reach the four bypass tubes necessary for emergency releases. Once sediment exceeds this level the dam and reservoir will need to be decommissioned to avoid compromising public safety. Despite this inevitability, and the impact it would have on recreation at GCNRA, no sediment management plan has been conducted for the reservoir area or dam operations. As noted below, sediment management is already becoming a major problem in the San Juan arm of the reservoir.

The only substantive work done to date by BuRec for sedimentation was conducted 15 years ago, The 1986 Lake Powell Survey. Although the data for this report is instructive, its conclusions are meaningless. The report states that the reservoir would completely fill with sediment by the year 2663 (700 years). As Weymouth stated for Hoover Dam, and Schultz for Glen Canyon Dam, accumulate sediment will eventually compromise the function and safety of the dams long before there is any chance that their reservoirs could actually fill with sediment. It's imperative that BuRec first determine when sediment accumulation will compromise the operation of Glen Canyon Dam so that other managing agencies, such as GCNRA, can better implement their own management plans, such as that for Hite Marina.

A technical memorandum was provided by Mussetter Engineering, Inc., on May 21, 2001 concerning sediment aggradation specific to the DCP for Hite Marina. The collection of data was completed in March of 2000 and included a reach on the Colorado River arm from ten miles upstream of the Dirty Devil River to .8 miles below North Wash, and a reach on the Dirty Devil arm ten miles above its confluence with the Colorado River arm. The data does not include a sediment study of North Wash Bay, which was also not collected during the BuRec 1986 sediment survey.

The memo states that the delta foreset slope will pass the boat ramp at Hite Marina by the year 2003. It also states the top of the delta builds up at a much slower rate and suggested that sediment would not impact access to the boat ramp for 35 to 40 years. However, the authors of the memo acknowledged that the results of their study did not include such variables as high volume freshets (for example, the freshets of 1983 and 1984), nor the mobilization of upstream sediments due to a lower reservoir pool as experienced between July 1990 and April 1993.

The authors calculated that by year 2003, the bottom of the bay before the Hite boat ramp would be 3630 feet. As of this writing the reservoir's elevation is currently 3660 feet. In April of 1993, the reservoir's elevation was 3610 feet. If such a scenario were to repeat itself, access to the boat ramp at Hite Marina would be completely cut-off in as little as two years.


BuRec's 1986 sediment survey provides some useful, though somewhat out of date, data to quantitatively evaluate the current rate in which the reservoir's deltas expand and encroach upon recreational infrastructure. The survey data would indicate that the Colorado River delta has now progressed into the bay at Hite Marina and that the Dirty Devil River arm is completely filled. Recent observations confirm that the tributary streams above Hite Marina, such as Gypsum, Dark and Clearwater canyons are also completely filled.

Unfortunately the report's data for sediment content in North Wash Bay is incomplete and should be gathered prior to any management decisions are taken for Hite Marina. This area drains a large area of soft Mesozoic host rocks that are allowing a sediment plug to form and encroach on the area just below Hite Marina. Over time, or in the case of one significant dump, sediment from North Wash will cause access to Hite Marine to be cut off by impeding the flows of sediment coming in from upstream. A similar problem at Hite would occur when the Dirty Devil River arm, completely full of sediment, ultimately deposits its contents into the reservoir.

A more immediate challenge is that the existing sediment plug from the Dirty Devil will cut off access to the existing camp developments in the area, as dam operations force the reservoir to drop. Lower reservoir pools are likely to become commonplace, especially over the medium term, with the implementation of the Interim Surplus Criteria. To meet ISC guidelines, Lake Powell reservoir will be drawn down more frequently to assist California with its off-stream storage plans. This is likely to be exacerbated by lower than expected precipitation patterns, and higher water utilization in the Lower Basin as is predicted by the Global Change Research Program.

Lower reservoir pools will significantly aggravate existing problems for river runners, which have historical precedence in the use of the recreational resources at Hite. It is already difficult to locate safe camps below Rapid #26 (Ten Cent). Popular hikes such as those conducted at Gypsum, Clearwater and Dark canyons on the Colorado River arm are very problematic because unconsolidated sediment restricts safe access, especially when liquefied. When the river incises the sediment at depth, such as what occurred in lower Cataract Canyon in 1992, hiking access is restricted due to unstable slopes of about 30 degrees. These impacts degrade the full value of the river trip experience and the associated financial commitment necessary to engage in such activities.

Such reservoir operations and sediment (mis) management issues have caused significant problems for Colorado River users at Pearce's Ferry on Lake Mead National Recreation Area (LMNRA). The low reservoir levels at Lake Mead, accompanied by the buildup of silt from the Colorado River above, made boating activities increasingly dangerous there this past season and forced the LMNRA to implement an emergency closure of the launch ramp.

Located near the top of the reservoir, Hite Bay will be one of the reservoir's first facilities to be inundated with sediment. How this will be managed, and how long before sediment will force its permanent closure must be addressed by the DCP to evaluate the merits of any additional capital expenditures. Furthermore, the DCP cannot strictly focus on the marina facility itself, but must develop plans to assure access for river runners, hikers and other users of the river corridors and side canyons in GCNRA's jurisdiction above the bay at Hite.


Another immediate and ongoing sediment management problem for GCNRA exists along the reservoir's San Juan arm. The San Juan River is the greatest single contributor of sediment to the Colorado River system. Historically, the San Juan River provided 15 percent of the Colorado River's annual flow and 35 percent of the sediment. The 1986 sediment survey indicates that the San Juan delta in Lake Powell reservoir is progressing at a rate of about 10% less than that from the Colorado River. Since the 1986 survey, the access at Piute Farms has been completely eliminated and has disenfranchised the Navajo Nation from generating revenue at that locality.

The access problem at Clay Hills Crossing is especially acute. When the San Juan River is low, access to the take-out is dependent on where the river channel is. Sometimes the river flows directly to the access ramp and sometimes it does not. River channels naturally migrate and abrade over sediment fill. When the channel migrates to the opposing side of the take-out, conditions mandate that the boaters physically carry gear and boats across the sediment. Such a task is unsafe due to the quicksand-like consistency. Senior citizens and disabled people especially experience difficulties with such a circumstance.

Another sediment-related problem occurs below Clay Hills Crossing when the reservoir is at low pool. Specifically, a waterfall emerges impeding further passage downstream. In 1992 the vertical drop at this waterfall was approximately 35 feet. The waterfall is a safety consideration to boaters and needs to be addressed in a more substantive way than a warning sign or educational brochure.

The eventual desiccation of the perched delta will cause the elimination of access to the boat ramp at Clay Hills. When the river channel at the waterfall migrates down the bedrock slope, it will excavate down into the delta and the river's gradient upstream will increase. When this occurs a deep, canyon-like slope of sediment will result at the boat ramp and extensive mitigation will be required. This will be costly and likely involves management decisions in consolation with the Army Corps of Engineers.

Gene Stevenson, a consulting geologist, outlined this problem to GCNRA staff in November of 2000 in Monticello, Utah, and in January 2001 in Page, Arizona. Mr. Stevenson also informed attendees that the San Juan delta was mobilized in 1983 and 1984, and deposited sediment as pulses into Zahn's Bay (40 miles from the confluence). The floods of 1983 and 1984 too contributed generous, fresh sediment in to the San Juan delta system.

At the Page meeting of January, 2001, GCNRA staff also heard from Dr. John Dohrenwend, a retired USGS surficial geologist. He displayed satellite image maps and explained that sediment has been accumulating in the arroyos and tributary stream channels of the San Juan River basin since the early 1940s. He explained that this is a natural occurring process for rivers in arid and semi-arid areas. For southern Colorado Plateau streams, this period of aggradation is very likely the result of a decrease in peak-flood discharge from these tributaries. At some point in the future, a regional climatic shift to more intense and frequent flood events will very likely occur. When intense storms return to the San Juan basin, the sediment deposits stored in the aggraded stream channels will be mobilized and carried into the main stem river system. Such a climatic shift could dump more sediment into the reservoir than what has occurred since Glen Canyon began filling in 1963.

Lake Powell reservoir inundates a total of 71 miles of the San Juan River canyon and its delta may soon reach its confluence with the Colorado. Because of San Juan sediment, mitigation pertaining to dam operations may be required prior to the period projected by Schultz in 1961. When the San Juan River sediment reaches the Colorado River confluence, it will effectively divide the main stem reservoir in half. During times of progressive down draw, this sediment plug will effectively leave the upstream half of the reservoir perched. Once formed, a breach of this plug would jeopardize GCNRA and BuRec infrastructures and could result in loss of life.


Another anticipated problem concerning sediment in the reservoir will occur for the facilities at Bullfrog Bay. Hall's and Bullfrog creeks have extensive watersheds in soft Mesozoic host rocks that have the potential to send massive sediment pulses into their respective bays after a significant meteorological event(s). The access road (531) that crosses Bullfrog Creek is underwater when the reservoir is at full pool. Sediment deposition from Bullfrog Creek will impact this access road in the coming years. This area has camp facilities at the head of the bay where Bullfrog Creek drains into the reservoir. Access to these facilities will also be impacted by reservoir sediment filling. The sediment plug will also eventually reach the marina and the ferry terminus.

Access to Rainbow Bridge National Monument (RBNM) will also be compromised when a sediment pulse occurs at Bridge and/or Aztec canyons. These watersheds originate in the Navajo Mountain watershed. More importantly, as Rainbow Bridge is a sacred site of the Navajo people, it would also be appropriate to include their spiritual elders in the processing of a sediment management plan. According to Executive Order 13007, the mandate for national agencies to do so is actually quite specific.

Though Antelope Point and Wahweap Marina are distanced from the Colorado and San Juan deltas, these boat launches too will be affected by sediment deposition from local tributary streams, compounded by the underwater turbidity flows that are currently building before the face of Glen Canyon Dam. The depth of Wahweap Bay averages about 230 feet and Wahweap Creek is an extensive watershed that drains soft Mesozoic strata from the Kaiparowits Plateau.

Antelope Point is located next to the original Glen Canyon gorge, which is about 530 feet deep when the reservoir is at full pool. However, the reservoir is quite narrow at this location and does not have an abundant storage capacity for sediment. Antelope Point lies between two drainages, Navajo Creek and Antelope Canyon, which drain large areas of soft Mesozoic rocks. These drainages already have progressive deltas building within their respective gorges. In 1997 a sediment pulse killed eleven visitors hiking in Antelope Canyon.


In conjunction with their General Management Plan, NPS entities often prepare more specialized management plans for issues specific to the natural environment and uses in a particular park, monument, or recreation area. As sediment is a major issue affecting present access in GCNRA, and ultimately the life span of much of its operations, it's vital that the agency undertake the preparation of a Sediment Management Plan as a component to its General Management Plan.

The study should be undertaken in partnership with BuRec, which itself has been delinquent in preparing a plan for addressing the impact of sediment on Glen Canyon Dam operations. The chief concerns in this regard are, one, that sediment storage displaces water storage capacity, and two, turbidity flows transports sediment before the dam's face. Displacement of water storage will stress the emergency spill criteria of the dam and turbidity flows will stress the mechanics of the emergency bypass tubes and power generation penstocks. Studies to date have not addressed how these problems are to be mitigated, despite representing a significant risks to dam operations. BuRec, should determine when and how such mitigation plans are to be implemented so that other management agencies, such as GCNRA, can develop their own management criteria.

In undertaking this work, it is vital that management agencies not focus merely on short-term trends. During the past 10,000 years, river valleys on the Colorado Plateau have experienced cycles of erosion and deposition having periods of decades to centuries. These pulses of cutting and filling are considered by most researchers to be closely related to the frequency and magnitude of large storms (100 year to 500 year flood events). Therefore the 40 to 50 year record of sedimentation in reservoirs, such as Lake Powell, are not necessarily an adequate basis for calculations of the rates and magnitude of sedimentation within these reservoirs, and for estimating the remaining useful lives of these reservoirs. Moreover, significant climate change is anticipated to occur during the next 100 years, and it is unresolved whether this climate change will bring larger and more frequent large storms (major floods) to the Colorado Plateau.

To this end, the plan must:

1) Determine the present distribution and thickness of sediment in Lake Powell and quantitatively compare these deposits with the 1986 sediment survey.

2) Contain detailed and consistent surficial geologic and geomorphic mapping and analysis of all Holocene deposits within the major watersheds tributary to Lake Powell.

3) Provide an updated analyses of sediment delivery to the reservoir via the main stem Colorado upstream of Hite and the San Juan River..

4) Estimate near term climate change on the Colorado Plateau (with special emphasis on the probabilities of significant changes in the frequency and magnitude of large storms; and estimate the potential impact of such changes on the possible mobilization of sediment deposits presently stored on the hillslopes, piedmonts, floodplains and river channels of the region.

5) Synthesize (and evaluate) all of the above with respect to potential sediment delivery to and deposition within Lake Powell.

Additionally, the plan must address water quality issues. When the river begins to cut into the sediment, it mobilizes heavy metals and toxins that originate from upstream industrial and agricultural activities. This includes toxins, which erode naturally from the host rocks upstream, such as uranium and selenium. Currently GCNRA does not have a management plan to address such potential human and animal health problems.


Lake Powell reservoir is a trap for sediment transported by the Green, Colorado, Dirty Devil, Escalante, and San Juan rivers (including numerous local side canyons). Hite Marina's future will be significantly impacted by ongoing sediment deposition, as will most of the development and recreational opportunities within GCNRA. Ultimately, as Schultz alluded to, increasing sediment accumulation in the reservoir will eventually force BuRec to make management decisions to address public safety problems associated with Glen Canyon Dam operations. These decisions will have a profound affect on the recreational infrastructures at GCNRA. It's critical that GCNRA address these issue directly, and prepare a management plan to guide its planning decisions as the reservoir continues to fill with sediment. We believe that the preparation of such a plan should take precedence over the completion of the Hite DCP, as the findings will inform future management challenges in the bay of Hite.

GCNRA should also direct immediate resources to address the existing sediment induced access problems at Clay Hills and elsewhere. This matter has been brought to your agency's attention in the past, yet no action has been taken. GCNRA is, however, proceeding with a variety of studies, such as the Hite DCP, Antelope Point EA and Wahweap DCP principally to benefit motorized users of the reservoir. The San Juan and Colorado River arms of the reservoir are also in the GCNRA's jurisdiction, and are used extensively by river runners.

We are concerned that GCNRA is displaying a culture of general avoidance to address the geologic processes concerning the public lands within its jurisdiction, as well as a preference for expanding services for high-speed recreation as opposed to river users.

We look forward to working with you to remedy this situation, and to ensure equitable and safe access for all visitors to the NRA.

Sincerely yours,

/ signed

John Weisheit

Conservation Director

And on behalf of the following organizations:

Colorado Outward Bound School
Colorado Plateau Rivers Guides
Four Corners School of Outdoor Education
Glen Canyon Institute
Grand Canyon Private Boaters Association
Sierra Club Glen Canyon Group
Utah Rivers Council
Utah Whitewater Club


Hon. Gale Norton, Secretary, Department of the Interior
Hon. Fran Mainella, Director, National Park Service
Hon. John Keys, Commissioner, Bureau of Reclamation
Hon. Kathleen Burton Clarke, Director, Bureau of Land Management
Hon. Kelsey Begaye, President, Navajo Nation
Elouise Chicharello, Regional Director, Bureau of Indian Affairs
Rick Gold, Director, Upper Colorado Region, Bureau of Reclamation
Carol DeAngelis, Grand Junction Area Manager, Bureau of Reclamation
Pat Schumacher, Durango Area Manager, Bureau of Reclamation
Karen Wade, Regional Director, National Park Service
Jerry Banta, Superintendent, Canyonlands National Park
Joe Alston, Superintendent, Grand Canyon National Park
Sally Wisely, Utah State Director, Bureau of Land Management
Nick Sandberg, San Juan Area Manager, Bureau of Land Management
Bob Hart, Research Associate, United States Geological Survey
Barry Gold, Director, Grand Canyon Monitoring and Research Center
Colonel Michael J. Conrad, Sacramento District, Corps of Engineers, US Army

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