Averting drought and disaster on the Colorado and Mississippi Rivers : Short Wave Historic drought in the west and water diversion for human use are causing stretches of the Colorado and Mississippi rivers to run dry. "The American West is going to have to need to learn how to do more with less," says Laurence Smith, a river surveyor and environmental studies professor at Brown University. He recently dropped in for a chat with Short Wave co-host Emily Kwong about how scientists are turning a new page on managing two of The United States's central waterways, the Colorado and Mississippi Rivers.

A course correction in managing drying rivers

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EMILY KWONG, HOST:

You're listening to SHORT WAVE from NPR.

Here's a fun fact. Two-thirds of the world's population lives alongside a river. That includes people in Washington, D.C., where I live.

We're here at the Potomac River.

The southern boundary of D.C. is cradled by two rivers, the Anacostia and the Potomac.

Millions of people live in its watershed. And I can just see the top of the water glinting in the light of the Kennedy Center. And obviously, there's a lot of traffic along the edges of the river - foot traffic, car traffic.

Life as we know it wouldn't exist without rivers. And Laurence Smith, professor of environmental studies and Earth sciences at Brown University, considers them part and parcel to human civilization. Rivers are everywhere, and their origins are ancient.

LAURENCE SMITH: Around 4 billion years ago, if not earlier, you know, rain began falling out of the sky. And water began to pool into lakes and seep into the ground. And water flowed over land and to rivulets and streams and rivers to newly filling seas.

KWONG: This water evaporated into the primordial atmosphere, creating water vapor, condensing into clouds and raining down again. Behold the early hydrologic cycle.

SMITH: Thus, rivers were born and began eroding the Earth's very early thickening continental crust.

KWONG: These rivers are concentrators of mass and energy among us, powering the places where humans have settled for hundreds of years. And in the United States, there's two rivers in particular that have been pushed to the brink - the Mississippi River in the East and the Colorado River in the West.

SMITH: With climate change, we are seeing sustained, very severe drought conditions which are persisting across the West that we now know through a whole group of scientific studies that have come out in just the last year or two, we would've had a drought anyhow. But it's human impact that has pushed it over the edge.

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SMITH: The American West is going to need to learn how to do more with less.

KWONG: Today on the show, reimagining our relationships to rivers. Laurence Smith and I talk about innovations in river science on both sides of the country and how our future is bound up to these flowing waterways. I'm Emily Kwong, and you're listening to SHORT WAVE, the daily science podcast from NPR.

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KWONG: OK, Laurence, first, we are seeing extreme and historically long drought right now in the West with segments of rivers drying up or ceasing to flow. What does this look like on the Colorado River?

SMITH: One of the hallmark impacts of climate change on the hydrologic system is more intense droughts and more severe floods. This is called intensification of the hydrological cycle. And plants get hot and dry. They need even more water, which they then transpire into the atmosphere. The soils of the Colorado Basin are getting drier. You know, there's a spectrum of models that are used, but, you know, we're looking at something like a 30% decline, further decline in Colorado River flows by the middle of this century. And possibly, by the year 2100, there may be half as much water flowing in the Colorado River.

KWONG: That is really devastating. It's a future that we haven't seen in our lifetimes. Do you think that there is an opportunity here for us to reevaluate our relationship to the Colorado River? What would that look like for you?

SMITH: Well, not only is it an opportunity. I think it'll be mandatory to reimagine our relationship with the Colorado River. There are really three ways, you know, and the first is underway - essentially, the cities buying out farming interests to increase their supply of municipal water because that's absolutely essential for life and its urban course, right? The second trend that's underway and just getting going is a whole variety of floodwater capture schemes. So the American West, unlike the temperate parts of the country - you know, many rivers are dry or nearly dry throughout much of the year. And then you get a few big storms in the winter, and those things are just raging. And they're a real flood hazard. Most of that water just flows out to sea. There's an exciting new trend which seeks to divert these floodwaters into catchment areas to allow it to percolate into the ground to be recovered later as groundwater.

KWONG: Whoa. OK. So you got water buyout programs. You've got flood capture, which is...

SMITH: Yes.

KWONG: I've never heard of such a thing. And what's the third one?

SMITH: One of the biggest problems facing renewable wind and solar energy is the so-called intermittency problem. When the wind's not blowing, when it's nighttime and the sun is not in the sky or it's cloudy, these sources shut down. And so a critical part of the renewable energy infrastructure is energy storage. And batteries are one part of that. But one outlandish idea is the idea of turning Lake Mead, you know, the Hoover Dam, into a giant, pumped energy storage facility. What this idea envisions would be to basically carpet the desert with solar energy and windmills and use that energy to pump water that has already flowed through the turbines of Hoover Dam back up into the reservoir. And that is latent hydropower just sitting there ready to be used.

KWONG: What you're saying is there's a proposal on the table to turn the Hoover Dam almost into a battery that can, like, store energy from the sun to power water through the dam and keep it there, that energy, for use later on?

SMITH: You said it perfectly. The idea is to turn the Hoover Dam into a $3 billion renewable energy battery.

KWONG: That's wild. These are really cool ideas. I now want to turn east to look at another storied waterway in our country, the Mississippi River. It is starting to run dry, or at least parts of it are seeing record low water levels. What is going on?

SMITH: This summer, the Mississippi has experienced an epic problem with low water levels. I mean, just a historic drought. And this is ground barge traffic and commercial traffic on the Mississippi - not to a halt, but it has severely curtailed it.

KWONG: Yeah.

SMITH: And this is still the main way in which the Midwest gets its agricultural grain exports out to market. We're in a time of severe food shortages around the world - the war in Ukraine, you know, bad weather - you name it. And so this this has been a real problem.

KWONG: Nearly 3,000 barges were backed up because of this. It seems like the problem has alleviated somewhat. But what does this tell you about the role that climate change-driven drought is playing and will play on the Mississippi River? Because I also - I got to say, most of what I know about the Mississippi River has to do with extreme rainfall and flooding. There's parts of the banks that are flooding inland communities. So hearing that there was low water levels really surprised me.

SMITH: Yeah, that's right. The Mississippi - it's always been a killer with floods. Climate change will cause floods to become more dangerous and droughts to become more severe. And so what this tells me looking forward is that one of the less discussed impacts of climate change will be threats to domestic shipping in internal waterways.

KWONG: OK, so that's what's going on in the Mississippi. What innovations or changes do you think would be required to reverse course?

SMITH: Rivers have tremendous power to move and deposit sediment. And traditionally, this has been thought of as a problem for shipping because when shoals form and channels fill with sediment, they block ship passage, and they have to be dredged. But a new school of thought in river engineering is to also look at the benefits of a river's power and ability to transport sediment, in particular harnessing that power in order to save disappearing coastal wetlands, which are being lost to sea level rise. The Mississippi River Delta in particular has been losing coastal land at an extraordinary rate. And at this very moment, a plan is advancing - a coalition of stakeholders in Louisiana and in the federal government and the U.S. Army Corps of Engineers - to harness the power of the Mississippi by breaking open the Mississippi River's levee in a key area called the Mid-Barataria Sediment Diversion, which would then move this sediment and allow it to flow into this area of disappearing coastal land and coastal wetlands and regrow it, rebuild it.

KWONG: That's - that is some next-level river engineering. It feels very out there. But then again, it was out there to disrupt waterways in the first place.

SMITH: It's actually taking a cue from nature. This is actually how rivers build floodplains and deltas on their own - is because they deposit in their own channel until they're higher than the surrounding land. Then eventually, a flood comes along. They breach their own levee, and they spill to lower ground, filling that up, as well. So this big $2.2 billion plan by the U.S. Army Corps of Engineers is actually mimicking a natural process called avulsion. Historically, we've actually gone through at least seven technological transitions with rivers before. And I think we're about now to begin an eighth, at least in the United States and Europe, where we are moving away from these major mega engineering projects like the Hoover Dam...

KWONG: Yeah.

SMITH: ...And instead tapping rivers with a lighter touch. And I think it's going to be an exciting eighth transition that will be happening over the next 50 years or so.

KWONG: Yeah. I love the way you look at rivers. You've looked at them from all sides, and that includes examining rivers from space? I understand that you're a part of a 20-year NASA research mission...

SMITH: Yes.

KWONG: ...To essentially 3D map the world's waterways.

SMITH: Oh, yes.

KWONG: It just launched.

SMITH: Thank you.

KWONG: (Laughter). Well, it reminds me almost of astronomy's efforts to map the stars...

SMITH: Yes.

KWONG: ...Which is super cool. But, like, why haven't we done this before with waterways? I was very surprised that this hasn't been applied.

SMITH: It's amazing. I've been working on this mission for over 20 years. It dates to my Ph.D. In fact, the first conference presentation I ever gave in my academic career as a graduate student was Can We Measure River Discharge From Space - question mark? And I was almost, you know, heckled out of the room for it for the idea. And now...

KWONG: Yeah.

SMITH: ...Here we are in 2022, and NASA and France are launching a $1.2 billion satellite to do exactly that.

KWONG: Right, yeah. So this new satellite - it is called the Surface Water and Ocean Topography mission, or SWOT. It launched on December 16. What is your hope for the data it will collect?

SMITH: This technology has the potential to be absolutely transformational because it will, for the first time in the history of humankind, map river levels and lake levels everywhere on the planet and post those data online for free. Believe it or not, most of the world's freshwater resources are totally unmeasured. So as you can imagine, we don't have a good handle on where our water resources are, how they're being stored, how they're being managed, how they're being moved around the Earth and certainly not across political borders. So SWOT will change that completely. I just am so excited to start receiving these data in the upcoming year and learning and understanding our freshwater resources around this Earth.

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KWONG: Laurence C. Smith is the author of "Rivers Of Power: How A Natural Force Raised Kingdoms, Destroyed Civilizations, And Shapes Our World." It is out now. Laurence, it was incredible to talk to you and to basically completely reimagine rivers with you. I really enjoyed our conversation.

SMITH: Thank you for the opportunity.

KWONG: Today's episode was produced by Abe Levine. It was edited by Rebecca Ramirez and Gisele Grayson. Rebecca also fact-checked, alongside Margaret Cirino. Robert Rodriguez was the audio engineer. Brendan Crump is our podcast coordinator. Our senior director of programming is Beth Donovan. And the senior vice president of programming is Anya Grundmann. I'm Emily Kwong. We're back tomorrow for more SHORT WAVE, the daily science podcast from NPR.

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KWONG: Oh, [expletive]. (Laughter) I just dunked my whole boot into the river. (Laughter). All right. Well, you wanted sounds of the river.

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