Long Term Decline of Sediment & Native Fish Initiate Proposed Experimental Flows for Glen Canyon Dam

Glen Canyon Dam and the Colorado River ecosystem continue to hit the news in the past few months. Long term monitoring now clearly shows that sand and endangered fish are in serious decline in the river ecosystem of Grand Canyon. The preferred alternative from the Glen Canyon Dam Environmental Impact Statement (eis) is not achieving a sustainable ecosystem as anticipated. This is frightening news for these two critical resources in the Colorado River ecosystem and the many other resources dependent upon them.
So what?
The driving principle of the Grand Canyon Protection Act of 1992 is to manage the dam “to protect, mitigate adverse impacts to, and improve the values for which [these national parks] were created, including natural and cultural resources and visitor use”.
Some selected quotes from the Glen Canyon dam Record of Decision (rod) follow:
“The goal of selecting a preferred alternative was…to find an alternative dam operating plan that would permit recovery and long term sustainability of downstream resources…”
“Nearly all downstream resources are dependent to some extent on the sediment resource.”
“Modified Low Fluctuation Flow is selected for implementation because it satisfies the critical needs for sediment resources and some of the habitat needs of native fish, benefits the remaining resources, and allows for future hydropower flexibility…”
“If impacts differing from those described in the final eis are identified through the Adaptive Management Program, the maximum flow restriction will be reviewed by the Adaptive Management Work Group and a recommendation for action will be forwarded to the Secretary.”
On sediment and endangered fish
In 1999, scientists presented a new and compelling sediment paradigm for the Colorado River ecosystem, which challenges fundamental assumptions of the Preferred Alternative of the eis and rod. Fine sediment is not being stored in the main channel for use in periodic restoration of sand bars and beaches. Some relevant facts follow:
Most of the river sand in Grand Canyon today comes from the Paria River and Little Colorado River, which supply about six percent of what entered the ecosystem before Glen Canyon Dam. Most of that sand enters the river in short flood pulses in the late summer/fall monsoon rainy season, and does so variably from year to year.
Sand is being eroded mostly from the upstream one-third of the river, stripping sand from eddies in the daily fluctuating zone (1.4 million tons in the past two years).
United States Geological Survey (usgs) cross-sections of the river channel show no net accumulation of sand in the channel with present dam operations. This is consistent with recent reports by sediment researchers.
Sand bar areas and volumes have decreased under Record of Decision flows. The Glen Canyon Dam eis predicted 73 percent chance of sediment accumulation in the main channel after fifty years with rod flows. Six years of monitoring data indicate no accumulation in the main channel, with continued erosion of sand from eddy complexes.
Habitat Maintenance Flows of power plant capacity (31,000 cfs) have not successfully stored sand in the channel, and have not mitigated loss of sediment from the eddy systems in the active fluctuating zone. Artificial flood flows can only store sand if there is available sand in the system to be deposited.
Grand Canyon Monitoring and Research Center (gcmrc) scientists recently produced population trends in humpback chub over the past decade. The population shows a precipitous decline since 1993. The causes are not well understood.
Predation of young humpback chub and competition for habitat by introduced fish like trout, carp, and catfish appear to be part of the problem.
The only known reproducing population of the Grand Canyon humpback chub is in the Little Colorado River.

Actions Taken
During 2001, a Technical Work Group (twg) committee led by Matt Kaplinski met to discuss the evidence on sediment decline. They put forth a proposal to the Adaptive Management Work Group (amwg) to address the problem. In January, 2002, Andre Potochnik worked with a group of environmental and recreational members of the amwg to produce and shepherd-through amwg floor motions as follows:
Amwg Sediment motion #1. Accept twg Sediment Report: The amwg concurs with the findings in the twg white paper A Report from the Technical Work Group Ad-hoc Committee on Sediment: Summary of Recent Findings and Recommendations for Future Actions.
Amwg Sediment motion #2. Design sediment conservation experiment for 2002–2003: In concert with the Reasonable and Prudent Alternative flows for native fish, during 2002–2003, request that the Grand Canyon Monitoring and Research Center (gcmrc), in consultation with the twg, design an experimental flow sequence that tests hypotheses for conservation of sediment. Report to amwg in April, 2002 on the proposed experimental flow sequence.
Consequently, gcmrc developed an experimental flow proposal for 2002–2003 that comprehensively addresses both sediment and native fish depletion. The proposal also recommends additional treatments over multiple years. This proposal establishes a strong rationale for dam release hydrographs designed to conserve sediment and disadvantage rainbow trout, with supporting efforts to mechanically remove predatory non-native fish from the river in selected areas. The first proposed gcmrc hydrograph with caption is replicated below.
Other hydrographs were included in the gcmrc treatment plan that were variations on this central theme, depending on whether sediment influx occurred, and when it might occur. We are not convinced that sand deposited by a large spike flow in January will be conserved by large fluctuating flows that follow in January–March. However, this is a difficult balancing act with the native fish. We understand their rationale and are willing to support their effort in the interest of doing good science and acting on real needs of the river ecosystem.
At the April amwg meeting, the gcmrc experimental flow treatment plan was condoned and gcmrc’s work was set out for them. Now the work really begins. This is a very low water year and minimum releases from the dam will occur. Time will tell as to whether the Paria River will deliver the necessary sediment for restoration of Grand Canyon beaches. They are in very bad shape.
This is a bold experiment. It is a major test of how well the Adaptive Management Program works; science informs policy, then policy is developed in response to that science. It is an iteractive process that will hopefully lead us to protecting a place that means so much to us all.
Gcrg is currently developing an amwg site on its web page and an amwg list serv so that we can hear from you. Thanks for your support.
Andre Potochnik
Adaptive Management Work Group
Matt Kaplinski Technical Work Group

note:
A year with significant sediment inputs would be defined as a period of 1 to 30 days during which the Paria River contributes at least its long-term, annual average input of sand (about 1.4 million metric tons, or greater), to the Colorado River. These inputs may occur as either one discrete flood of many cumulative inputs over the course of a month.
In every scenario where a bhbf is proposed to be released in January 2003, the bhbf should have a magnitude of at least 10,000 cfs above peak powerplant discharge, or higher depending on lake elevation.