- Major rivers all over the world are drying up.

Many are in regions that are experiencing multi-year droughts with levels of water storage and reservoirs reaching historic lows, exposing artifacts, sunken boats, and human remains.

The reason for extreme drought in so many different places is largely the same.

Average air temperatures are rising and warmer air holds more water.

That means less water falls to the ground and more of what does fall evaporates before reaching creeks, rivers, and reservoirs.

Instead of condensing and precipitating, it stays in the atmosphere.

We've talked about these changes to our hydrologic cycle before on weather, but it wasn't until this episode that I learned that the moisture capacity of air doesn't just go up with temperature, it goes up exponentially.

So, even if the rate of warming stays the same, the rate of change in our water cycle becomes faster and faster.

And this is pretty scary, because we use water for everything from growing food to drinking, to generating electricity and manufacturing.

In this episode, we're going to look into what these regions and their important food producing areas will look like as their rivers continue to dry up, and their reservoirs empty.

(dramatic thud) Okay.

First, a quick look at some globally significant drought areas.

The Yangtze River in China is the world's third largest by volume.

In 2022, it hit levels so low that power generation was cut off causing rolling blackouts during a historic heat wave.

Europe is experiencing the most severe drought in 500 years.

Danube, essential to the region's economy, transportation, and agriculture is running 50% below normal summer levels.

In the U.S., the Colorado River supplies freshwater to over 40 million people and very important farmland, especially for winter vegetables.

On average, it's flowing at levels 20% below normal, which has caused the nation's largest reservoir, like Mead to drop to its lowest levels since it was filled in the 1930s.

To get an idea of what these regions will look like when their most significant river systems run dry, we're going to look at pretty drastic changes already underway in the Colorado River Basin.

But first, let's ask Teal, who you might know as Western Water Girl, how on earth all those people rely on one river?

- [Teal] So, Lake Powell and Lake Mead and all of the other storage projects in the Colorado River Basin are meant to act as savings accounts.

So they store up extra water in the years that we have access water to provide for the lower basin states in the years that we don't have as much water.

And then there's, basically, a very complicated series of canals to deliver this water to namely irrigators, but it also goes to municipalities.

But, unfortunately, in the late 1800s and the early 1900s we did have an unusually wet period, and there was a lot of excess water in the west, and we made all of our allocations based on that period.

- Specifically, 17 million acre feet per year.

- But based on trending data, we know for the last 900 years that the average flows in the Colorado River Basin are only 14.3 million acre feet.

So that creates a huge deficit within the entire system to start off with.

And then on top of that, flows are diminishing because of climate change.

And between 2000 and 2020, it was only 12.4 million acre feet.

- [Maiya] Today, Lake Mead is down to nearly 27% of its capacity and if we keep drawing more water than the River provides, the intakes for irrigation and municipal pipelines, we'll be left high and dry.

Also, Hoover Dam will stop producing power.

Sorry, Las Vegas.

(upbeat music) It's a city of extremes, a human made oasis in one of the country's hottest and driest places and one of the fastest growing cities in the U.S. - Our system is reaching a breaking point, and so, federal officials did come out and ask the Colorado River Basin states to come up with a solution to reduce consumption by 25% by next year.

- But surprisingly, John Entsminger, the water manager for Southern Nevada, is not concerned.

- These reductions, actually, don't have any effect on us at all.

We still have extra water that we're banking in Lake Mead.

(tire screeching) - Wait, what?

How is that possible, when Lake Mead is at record low levels?

Well, it turns out that even as the city has grown, it has managed to decrease water use.

- We've added, since 2002, about 750,000 new residents and we're using 26% less Colorado River water than we were two decades ago.

- So, say what you will in the comments about a rapidly growing city in the middle of a parched desert, but they're doing a pretty amazing job of water conservation.

And strangely, other cities in the basin would probably do well to adopt some of what they're doing.

- Probably the most important thing that we've done is realized that you can't have a lot of extra grass in the desert.

So we've been paying people to remove turf, and we've actually taken out enough grass in this valley to lay an 18 inch wide piece of solid all the way around the circumference of the globe.

We've now, actually by state law, made watering nonfunctional turf illegal by the end of 2026.

Indoor water usage is essentially a hundred percent recycled.

So, if it hits a drain in southern Nevada, we clean it, we put it back in Lake Mead, and we can take it right back out again.

So, it's all of the above approach in terms of trying to be the most water efficient city in the world.

- [Maiya] But let's go to irrigation enforcement for a moment because part of what it means to live in a landscape drying out is actually getting tickets for using your sprinklers wrong.

- [Perry] Yeah.

Okay.

Irrigation system leak west side of the property.

I'm a Water Waste Investigator for the Las Vegas Valley Water District, and I patrol neighborhoods and look for water waste, and help folks fix problems as I can.

I happen to be driving around the neighborhood this morning, and I saw some water coming off the property, which is a definition of water waste.

Water that is used indoors and whatnot, it is recycled.

The water that goes down the gutter is lost, pretty much forever.

And so, I stopped to find out that it was a irrigation system leak in two spots.

One was a pretty good size one, probably a good five to 10 gallons per minute.

And so I wrote it up.

I gave them a warning, hey, please fix this.

And we will follow up a week later to see if it has been fixed.

- So even if cities affected by drought can continue to deeply cut water use without all that much disruption, all that work won't feed the people of Las Vegas, or the rest of the world.

And that's where the biggest changes will come, probably soon.

- [John] When you look at the Colorado River Basin as a whole, you have about 20% of the water going to municipal and industrial uses, and about 80% going to agricultural uses.

And when you look at the 80% of river use in agriculture, 80% of that 80% is going to alfalfa, and other hay products for forage.

So when you're talking about needing to reduce total system uses by 25 to 30%, it's just not possible to do, unless you reduce the amount of water that's going to those different species of grass.

I was asked when I was testifying in front of the U.S. Senate, if I could do one single thing, what would it be?

And my answer was a massive investment in agricultural efficiency, because we do need to continue to produce these products, but we can't continue to do it using the same technology that the Pharaohs used to grow cotton in the Nile Valley 7,000 years ago.

- So what would it take to make this change to more efficient systems of crop irrigation?

- The main purpose of our research program is to try to understand how to maintain high crop yields with less water.

- [Maiya] Most farms in the basin either irrigate by flooding their fields or by center pivot systems, but those systems over water some parts, and underwater others.

- Center pivots have technology that allow each nozzle to vary on and off.

Typically, when that technology is used right now, they use soil maps and yield maps from the past, and they create zones.

What we're looking at is something that's a little more close to real time.

And within each plot, we will take soil moisture measurements.

We have infrared thermometers.

They scan an area in the field and tell you what the temperature of the plant is.

And we can use that to quantify how much water stress there is.

So you can drop the water use by up to 20% in some cases without losing a lot.

- I think it's really awesome that we've made such technological advancements, and I agree that that's a really important part of this puzzle, but I think it's really important for people to understand that technology alone will not solve this problem.

Even if a farmer upgrades from flood irrigation to drip, or sprinkler irrigation, any of the savings created from that upgrade are just passed along downstream to the next user.

And there's no way for that farmer to be compensated for those changes.

And that literally discourages farmers from making efficiency improvements.

And until we address that problem, we're not gonna be able to solve this crisis.

There is physically no way for us to reach the 25% reduction goal without getting agricultural on board.

And with the way the system is set up right now, the only way to do that is to pay them to fallow their fields.

And if we do that, It's gonna lead to large and small agricultural communities being bought out and dried out, and those communities will literally die.

It's really, really sad.

We are already seeing the effects of this in the basin, especially in Arizona, where they just faced a mandatory 21% reduction of their water allocation from the Colorado River.

There are already farmers in Arizona that are being forced to fallow their crops.

And in my mind, if we're already gonna pay those irrigators to not irrigate, then why don't we just pay them to adapt?

It's just gonna have to be different crop choices.

We can't have as much cattle as we have right now, and we can't be growing as much alfalfa as we have right now.

We can't be growing 200,000 acres of cotton in Arizona with flood irrigation.

I'm not saying we can't grow food in the southwest, I'm saying that we need to rethink the way we grow food in the southwest.

- [Maiya] Will we shift away from high water crops like alfalfa that feed cattle for beef, or will we innovate and continue business as usual with new technology?

(gentle music)