GCES: It Aint Over til its Over
The Glen Canyon draft Environmental Study is a weighty document.
Within its covers lies the analysis of ten years of research into one of the most complex
and wonderful systems on earth. It is far from perfect, even today our understanding is
limited. And regardless of the decision that will be made by Secretary Babbitt our
understanding will continue to improve. As important is the fact that this decision is not
simply up to the scientists and politicians, those that know and love the Canyon have a
say as well. We hope open debates such as this continue to grace these pages.
Weve said many times that well start worrying when noone cares
enough to make a few constructive criticisms. Were still not worrying.
Now I see the errors of my complacency. I was just
waiting for the Draft Glen Canyon EIS (DEIS) to come out with some answers for me. I
should have been staying involved, questioning more during mid investigation - not just
picking up on a few things, helping out here and there - hoping for a clean result. While
many people seem to be congratulating the entire EIS process and all of its participants I
question why the Modified Low Fluctuating Flow(MLFF) was chosen as the preferred
alternative. In comparing the impacts of each alternative on downstream resources, the EIS
predicts that some form of steady flows will be the most positive.
I have great hopes for the experimental beach building floods. My main
concern, especially above the LCR, is will there be enough sediment in the system? The
DEIS says that of all the alternatives, the potential to accumulate sand in the system is
highest under steady flows. Increasing riverbed sand increases the chances of the beach
building floods actually working to aggrade sandbars versus acting as a clearwater, i.e.
erosive, flood. And how do we prevent frequent or unscheduled floods? I recommend we
implement BOTH methods of reducing flood frequency suggested by the DEIS; not just one or
the other. I think clearwater floods should be avoided. Why not maximize our insurance by
maximizing sand accumulation with one of the steady flow regimes?
I was on the river in Feb./March 1993 when floods from the LCR dumped new
sediment on top of existing sandbars almost everywhere downstream. By July interim flows
of about 20,000 cfs returned and we watched many of the new deposits eroding quickly. I
suggest that whichever alternative is chosen, the normal daily maximum flows need to be
capped at no higher than 13-15,000 cfs. It seems to me a lower normal daily maximum cuts
into the higher deposits not only at a lower elevation, but with a lower energy too, thus
better protecting and restoring this downstream resource as required by the Grand Canyon
The GCRG summary of the DEIS states ...mounting evidence of damage to
Canyon beaches due to severe fluctuations in releases from the dam... Another
investigator states that ...sand was accumulating in the river system during the
interim flow period... and ...significant erosion occurred during all of the
constant flows (8,000, 11,000, 15,000).... The DEIS says that the potential to build
sandbars is highest under the higher fluctuating flows, but net accumulation in riverbed
sand is lowest. Conflicting interpretations from the same set of data? I dont know.
What I do know is that constant flows were evaluated after only an 11 day period of each
constant flow regime. This is not enough field information to make conclusive statements
about significant erosion or greater probability of net gain in riverbed sand. I also
remember that constant flows research was conducted during a relatively mild period of
sediment input from the Paria and LCR (Oct. 1990-May 1991) while weve seen much
higher sediment input over the past two years of interim flows. Had constant flows
research been conducted during this higher sediment period, would they also have shown
sand accumulation in the river system?
So what about the fish? Maybe the chub is doomed regardless of dam operations
due to exotic predators, but maybe not. I am not advocating single resource management of
GCD; but the humpback chub is important. As far as anyone knows, the only place on the
planet this species lives is in the Colorado River. It evolved in the old river system and
is as much a part of Grand Canyon as the Monument Fold. Hopefully, whether Secretary
Babbitt goes with MLFF or a steady flow alternative (and both with capped daily maximums!)
the steady flows built into the MLFF for endangered fish research would last long enough
to provide some valuable and usable data.
The above concerns leave me uneasy about decisions being made and the real
life function of the Adaptive Management Work Group. Why werent steady flows with
habitat maintenance flows the preferred alternative over MLFF? I hope it wasnt
simply because MLFF had less of an impact on the post-dam marshes or allowed for fairly
cheap power Are these the resources we are choosing for? Not my choices.
Perhaps we should applaud the success of consensus building and cooperation
reported throughout this EIS process. Maybe our culture is slowly starting to put more
value on naturalness and non-use values. The DEIS says any findings of the non-use values
study will be published in the final EIS. I hope so. Until then were left with our
love for the Canyon and the desire to do good for it. All I can say is keep questioning,
dont become complacent. Stay and become more involved than I did.
The Draft EIS is just that, a draft. A
preliminary sketch, outline, or version (Websters Dictio nary). Ive read it
several times and have to agree with some of Mimis comments. I agree with EIS
teams decision, but dont think theyve done a good job of explaining how
they came to it. What Ill try to do here is point out some of the problems I have
with the DEIS analysis and explain why I support the preferred alternative.
The estimates of the probability of riverbed sand accumulations used by the
EIS team are based on a simple sand balance equation: [what comes in]-[what goes
out]=[whats left]. Colorado River sand loads were computed using the sand-discharge
equations developed during GCES Phase I and tributary input was assumed to be the same as
historical patterns. The 20 and 50 year predictions were calculated only for the reach
between Lees Ferry and the LCR. I think an estimate of the error involved in these
predictions should be computed as well. For example, is the difference between the
probabilities of sand accumulation after 20 and 50 years between MLFF and SASF significant
(64 and 73% vs. 71 and 82%) ? If available, error estimates would make a big difference in
how to interpret these results.
The comments I made in the GCRG perspectives article supporting the preferred
alternative were based on the results from repeated topographic and bathymetric surveys.
During the test flows our analysis was mainly focused in the hydrologically active
zone (HAZ), a zone directly affected by dam releases between the discharge range of
normal operations (3,000 to 30,000 ft3/s). We measured a loss in sediment from this zone
during the constant test flows at a significant number of our sites. Unfortunately, we
observed the same pattern of erosion, although not as much, in the HAZ during the low
fluctuating test flows!
For what its worth, here are some observations on the difference between the
two. The bulk of the erosion that we observed during the constant flows occurred when
cutbanks developed and retreated at the waters edge. During the low fluctuating flow
regimes (both the test flows and interim flows) cutbanks eroded most rapidly at the peak
of the fluctuation. In general, cutbank erosion rates decreased when the water elevation
dropped below the base of the cutbank. The constant flows are more erosive because the
erosional front at the waters edge is sawing away at the base of the cutbank for a
longer period of time than during low fluctuating flows.
But what do we know for sure? We now have more than two years worth of solid
observations, not probabilities, to prove that sand has accumulated under water during
interim flows. Since the test flows we have expanded our observations beyond the HAZ to
the entire river channel surrounding our study sites. These surveys have proven that sand
has accumulated in both the eddy systems and in the main channel during interim flows. But
at the same time, erosion of sand from the higher bar elevations was not replaced. Above
water, the foundation of the riparian ecosystem (sand bars) is being eroded. Below water,
sediment is being stored, but some of it is accumulating in important native (and
non-native?) fish habitat. Big problem. The answer: flood flows. The prediction, and hope,
is that high flow releases will replace lost sand on top of the bars, re-excavate the
backwater habitats, and demonstrate that the dam can be used to manage for a healthier, if
not entirely natural, ecosystem. We saw how the LCR floods last winter built sand bars
downstream. The higher flows scheduled next spring will push stored sand up higher and
further back than the LCR floods so that it will hopefully stay around longer.
I support the preferred alternative because it builds on what we know works,
gives us the opportunity to see if steady flows will work, and allows the adaptive
management team to pull the plug on any scenario thats not working. In addition to
the GCRGs concerns over the Adaptive Management and long-term monitoring aspects of
the DEIS, we should demand that the EIS team make it clear how they chose the preferred
alternative. The EIS team should also supply a comprehensive bibliography of the reports
and publications generated by the studies and to not simply reference written
communications from the Principal Investigators. The process has just begun and it
doesnt end with the final EIS. Stay involved, be critical, be a part of the