Opening a Dam to Study and Improve Resources in the Grand Canyon

Dave Hebert

This episode of CoreCast was brought to you by the following sponsor.

[people on elevator: Jenn LaVista, Scott Horvath; narrator: Dave Hebert]

[sound running feet approaching]

Scott

Whoa, hold the elevator! Thanks—oh, hey, Jenn, how are you?

[elevator door chime and doors closing sounds in the background; elevator music begins and continues throughout]

Jenn

I'm good . . . um, I'm sorry, do I know you?

Scott

Yeah, I'm Scott—we worked together on the Gold Harvest account for six months last year.

Jenn

Oh...OH, right. [quickly and nervously] Oh, my gosh. I'm so sorry. I'm really bad at names, and I didn't get a good night's sleep, and I was a half-hour late today . . .

Scott

[quickly muttering after Jenn says "I'm so sorry."] It's . . . OK. You only said that I had some of the best ideas on the team and that you hoped we could work together again . . .

[several seconds of silence]

Jenn

So . . . did you know that volcanoes can affect the weather?

Scott

OooKay . . .

Jenn

Yeah, um, the 1991 eruption of Mount Pinatubo, in the Philippines, resulted in a large volcanic cloud that drifted around the world. And that cloud had about 22 million tons of sulfur dioxide in it, which combined with water to form droplets of sulfuric acid, keeping some of the sunlight from reaching the Earth and thereby cooling temperatures in some regions by as much as 0.5 degrees Celsius, or almost 33 degrees Fahrenheit.

Scott

Really?

Jenn

Yeah.

Scott

[elevator bell rings and doors open]

Wow. All right. Well, thanks—I'll see you later.

Jenn

See ya.

[doors close]

Narrator

Fill an awkward silence with some science. Learn how by going to usgs.gov/podcasts and listening to CoreFacts. CoreFacts: It's short on time, and big on science.

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Music credit

"begin" by duke16

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Jennifer LaVista

Welcome, and thanks for listening to the USGS Corecast. I'm Jennifer LaVista. The Department of Interior has proposed an experiment using high flows from Glen Canyon Dam to study and improve Colorado River resources in Grand Canyon National Park.

Joining us on the phone is USGS Grand Canyon Monitoring and Research Program Chief John Hamill, who will be telling us more about the high-flow experiment and what the potential benefits may be. John, thanks for joining us.

John Hamill

Good moring!

Jenn

Good morning! Now, first off, can you tell me—what is a high flow experiment?

John

Sure, but a little bit of background first: Glen Canyon Dam is a major dam that was built and is operated by the Bureau of Reclamation on the Colorado River. It's immediately upstream of Grand Canyon National Park. High flows in the Colorado River system normally occur each spring as the snow in the Rocky Mountains melts.

Those high flows are now captured by Glen Canyon Dam. The dam also blocks most of the sediment that used to come down the Colorado River, which has resulted in the erosion of many sandbars in the Grand Canyon. Sandbars are used extensively as camping beaches for people. They also provide important habitat for native fish that utilize small protected areas—so-called backwater habitats—that form next to these sandbars.

Young native fish like the humpback chub are hypothesized to use these habitats in their very early life stages because they are significantly warmer than the main channel and they offer opportunities for them to grow faster. In addition, sand from these sandbars gets blown up onto the shoreline and may actually help protect archaeological sites.

Over the past 18 months or so there has been large amounts of sediment that has been deposited in the Colorado River below Glen Canyon Dam by flooding on several major tributaries. Much of that sediment is now sitting at the bottom of the channel of the Colorado River. This high flow that we're planning will mobilize that sediment that's at the bottom of the channel and deposit it up on the shorelines to recreate or replenish sandbars in the canyon.

Jenn

OK. So tell me a little bit more about the benefits that you hope to see from this experiment.

John

We would expect that more sandbars would be created throughout the canyon, that those sandbars would be larger and more broadly distributed then they are now, and that there would be more of these so-called backwater habitats formed in conjunction with those sandbars. We would also expect more sand would get blown onto the shoreline and help protect archaeological sites.

I also think that the high flows would scour the river channel and stimulate greater productivity of aquatic food that native and sport fish, like trout, depend upon. Those are some of the major benefits I think that we would hope to or expect to see as a result of this study.

Jenn

Now, you mentioned increasing sandbars. What are the importance of these sandbars?

John

Well first of all, they were kind of a major component of the Colorado River and the Grand Canyon before the dam existed. If you look at old photographs of the canyon before the dam, sandbars were just extensive throughout the canyon area. They were a major feature of the canyon. They have been greatly reduced in size and distribution as a result of the construction of the dam.

So their importance today is that they provide that habitat for native fish, they provide those camping areas for people who go down the river on rafts and hike along the canyon—they camp on these areas. They also provide a place where vegetation can grow, which supports a lot of the bird life and reptiles and other wildlife that exists along the river corridor.

Jenn

Can you tell me a little bit more about the endangered humpback chub?

John

The endangered humpback chub is one of the . . . actually a handful of native fishes that used to exist, or still does exist in the Colorado River System. It's a very interesting fish—it's called the humpback chub because it has a very pronounced hump on its back. It grows to about 14 or 16 inches in size. It lives up to 40 years of age.

Jenn

Forty years?

John

Forty years. And it's actually evolved to live in highly turbulent and turbid river systems. Only five populations exist within the Colorado River Basin today. The largest is within the Grand Canyon. It is protected by the Endangered Species Act. And one of the hopes is that these high flows will contribute to their recovery by creating some of these habitats—so-called backwater habitats—that the young fish . . . we know they utilize those backwater habitats really extensively. What their overall importance is to their overall survival is kind of yet still one of those things that we're still trying to determine.

Jenn

So John, tell me about what's going to take place on March 5.

John

Well actually, beginning on March 4th, the flows from Glen Canyon Dam will be gradually increased up to a peak of about 41,000 cfs (cubic feet per second). This is about 3 to 4 times the normal release that comes out of the dam.

Jenn

Wow!

John

Which may seem like a whole lot of water, and it is, but it's still about a third of what has occurred there historically before the dam existed.

Jenn

Really?

John

So, its much more in comparison to what exists today but it's not nearly as great as what was there historically. But at any rate, we're going to ramp up the release to 41,000 cfs. We're going to leave it there for 60 hours—about 2 and a half days—and then we'll gradually ramp it down again on March 9th.

Jenn

OK. Now I understand that this is a multi-agency event. Who else is participating in this experiment?

John

This really is a multi-agency effort. The U.S. Geological Survey has the principal responsibility for conducting all of the scientific studies. We'll have over 100 researchers in the field studying various aspects of the experiment. The Bureau of Reclamation is the principle agency that operates the dam and regulates the flows that come out of the dam. The National Park Service is obviously involved in that the resources we are trying to benefit are all either within Glen Canyon National Recreation Area or Grand Canyon National Park, which are both immediately downstream of the dam.

And then the other entity is the Glen Canyon Dam Adaptive Mangement Program, which is a 25-member, so-called Federal advisory committee that advises the Secretery on how to best operate the Glen Canyon Dam. It includes a variety of stakeholders, including hydropower interests, recreation interests, environmental groups . . . all of those States in the Colorado River Basin are represented, six Native American tribes are involved in that process. And we worked a lot with that group over the last couple of years in developing the science plan that we're going to be implementing over the next several months.

Jenn

OK, great. So, how is this different than previous studies done at the dam in the past. I understand there was one done in 1996 and then in 2004?

John

Yes, this will be actually the third of these experiments. And just by way of review, the first experiment that was done in 1996 was based on the assumption that the sand that comes in from tributaries below the dam actually just kind of accumulates on a continuous basis in the bottom of the river.

And when we did this experiment in 1996, it turned out that there was actually very little sand in the system. Most of that sand had been transported downstream just by the normal operations of the dam. And so we did not get a very good response from sandbars and some of these wildlife habitats that we were trying to create.

And that led to the 2004 experiment, where we tried to do . . . where we actually did the experiment immediately following some of these tributary floods, which we knew deposited some significant amounts of sand in the river channel. What we saw there was that we got a very positive response immediately downstream of these tributaries.

But many areas of the canyon did not see many benefits as a result of that test. And so what we have this year is we received 2.5 million metric tons of sand that have been introduced into the Colorado River over the last 16 months.

Jenn

How much sand? Can you give us an idea of what that would look like?

John

Sure. If you can imagine a 100-story building the size of an NFL football field, that's roughly how much 2.5 million metric tons would translate to.

Jenn

So if you were to go up 100 stories in a football field—it's that much sand?

John

Yes, exactly. Yeah, it's a big pile of sand. And we believe that sand, since it's kind of come in progressively over that 16 months, is actually distributed over a much broader area of the Grand Canyon then it was previously. So our expectation is that we'll see some positive responses in terms of sandbar building but over a much broader area than we saw in 2004.

Jenn

So, when will we know the effects of this experiment?

John

Well, I think some of the effects will be kind of evident immediately after. We'll be able to see where sandbars were created. We've collected data and information prior to the high flow. In fact, some of the trips have recently come off the water gathering information about what the condition of the resources are before. There will be data collected immediately afterwards and then actually all the way through next fall.

We would expect that results would be forthcoming early 2009 and that there would be actually complete synthesis of all the results sometime in 2010, and in that synthesis we would actually compare the results of this study with the work that was done in 1996 and 2004.

Jenn

Do you think there will be more high flow experiments needed in the future?

John

We were asked, within the USGS, by the Department of the Interior to develop this experiment. This experiment is being done as a response to a request that we received from the Department of the Interior to evaluate the effects of a high flow in the Grand Canyon.

We work with the Glen Canyon Adaptive Management Program in determining whether or not additional tests are prudent. At this time, we're committed to evaluating the results of this test. Really, the number of tests and when they're done is a management decision that's made by the Department of the Interior in consultation with the Adaptive Management Program.

Jenn

John, is there anything else you'd like to add?

John

No, I can't think of anything. I think that covers most of the major aspects of what we were planning to do.

Jenn

Well, great! Thank you so much for joining us.

John

Thank you very much; this has been fun.

Jenn

It really has. And thanks to all of you for listening to this episode of CoreCast. You can find out more information by logging onto www.gcmrc.gov and clicking on the high flow experiment tab. CoreCast is a product of the U.S. Geological Survey, Department of the Interior. Until next time, I'm Jennifer LaVista

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Music credit

"100 BPM-Bassline A" by frifrafro

Mentioned in this episode

• News Release: Reclamation Releases Final EA and FONSI Authorizing High-Flow and Steady Flow Experiments on the Colorado River
• Grand Canyon Monitoring and Research Center
• humpback chub
• Bureau of Reclamation
• National Park Service
  • Glen Canyon National Recreation Area
  • Grand Canyon National Park
• Glen Canyon Dam Adaptive Management Program
• CoreFacts

 

Click the image to the left for a high-res view of Glen Canyon Dam's jet tubes in action.