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Amy Quinton 

Hey Kat, welcome back to Unfold.

 

Kat Kerlin 

Great to be back Amy. What are you doing with a basketball in a studio?

 

Amy Quinton 

What this? I thought I'd just, you know, shoot some hoops.

 

Kat Kerlin 

There are no hoops in here.

 

Amy Quinton 

Well, I brought it as an audio and a visual aid.

 

Kat Kerlin 

And what am I trying to visualize exactly besides you playing basketball?

 

Amy Quinton 

Did you know that one basketball is about a quarter of a cubic foot in volume? So for these basketballs is one cubic foot!

 

Kat Kerlin 

I'm struggling to think of a ball as a foot, let alone a cubic one.

 

Amy Quinton 

Okay, well imagine this basketball is full of water.

 

Kat Kerlin 

I think I see where you're going with this analogy. We're going to be talking about water.

 

Amy Quinton 

That's right groundwater, the water in our aquifers. Jay Lund gave me this analogy actually.

 

Kat Kerlin 

He founded our Center for Watershed Sciences. He's also an engineer, so kind of likes to do math.

 

Amy Quinton 

Yeah. So let me throw some numbers your way. Over the last century, California has lost 120 million acre feet of groundwater from Central Valley aquifers.

 

Kat Kerlin 

So that's the amount of water that Californians have over pumped from aquifers. And what's an acre foot again?

 

Amy Quinton 

An acre foot is enough water to cover an acre of land a foot deep. So we're talking about 120 million acre feet over the last century in the Central Valley.

 

Kat Kerlin 

Wow, I just can't imagine that. Is that like overdrawing $120 million from my bank account or something?

 

Amy Quinton 

Yeah, if you want to consider groundwater a bank account, but back to the basketball, let's start smaller. How about imagining 2600 basketballs? Can you imagine that?

 

Kat Kerlin 

Kind of

 

Amy Quinton 

Just because it's a lot. It's difficult.

 

Kat Kerlin 

It is a lot. So you're comparing our groundwater overpumping to 2600 basketballs?

 

Amy Quinton 

No, it's actually 2600 basketballs for every person living on earth today, just in the Central Valley.

 

Kat Kerlin 

Whoa,

 

Amy Quinton 

Yeah. Hydrologist Thomas Harter with ºÙºÙÊÓƵ says it's not sustainable. We're over pumping about 2 million acre feet a year now in the San Joaquin Valley.

 

Thomas Harter 

With the megadrought that we are experiencing currently, you know, even with these rains not right now, that problem has been exacerbated and probably extended to other places in California.

 

Kat Kerlin 

Yeah, the megadrought. So that's a good reminder that just because we've had a parade of atmospheric rivers and snowstorms this winter and spring, doesn't mean we no longer worry about drought. Just last year, farmers didn't plant many of the crops they normally would.

 

Amy Quinton 

Yeah, I met a farmer that fallowed land this year. Nick Edsall, he's the orchard manager for Bullseye farms in Yolo County.

 

Nick Edsall 

We removed walnut trees this year because the markets just really bad. And we feel like we need to use our resources, especially water resources for other more valuable crops.

 

Kat Kerlin 

He removed even permanent crops, like nut trees?

 

Amy Quinton 

Yeah. 500 acres of young walnut trees. And like a lot of farmers, Nick relies primarily on groundwater, especially in a drought here.

 

Nick Edsall 

With a lot of permanent crops coming in, it's put quite a demand on on groundwater. And without any surface water the last few years, we've been running low. Every year, we're just crossing our fingers hoping that we don't have problems or run out of water.

 

Amy Quinton 

Most farmers turn to groundwater during droughts,

 

Kat Kerlin 

But increasingly, farmers are not only finding ways to conserve groundwater, but also capture stormwater to help replenish thirsty aquifers.

 

Amy Quinton 

But managing groundwater in this extreme climate is a huge undertaking. In this episode of Unfold, we'll examine how ºÙºÙÊÓƵ scientists are working to make groundwater more sustainable and help California remain the most productive agricultural state in the nation.

 

Amy Quinton 

Coming to you from ºÙºÙÊÓƵ, this is Unfold. I'm Amy Quinton.

 

Kat Kerlin 

And I'm Kat Kerlin.

 

Kat Kerlin 

Just last year, UC researchers found that farms pumped 27% more groundwater than in 2019.

 

Amy Quinton 

Groundwater overpumping has caused lands to subside or sink it's reduced water quality and resulted in higher energy costs to pump water from even deeper wells.

 

Kat Kerlin 

It dried up some wells forcing some communities to go without a clean source of drinking water.

 

Amy Quinton 

State law now requires managers of the state's most depleted aquifers to bring those basins into balance by 2040.

 

Kat Kerlin 

Well, no silver bullet exists. But scientist at the ºÙºÙÊÓƵ Agricultural Water Center are working with farmers to find solutions. They have more than 15 research sites in the Central Valley alone.

 

Amy Quinton 

One of those sites is a pistachio orchard on Nick Edsall's farm in Yolo County.

 

Amy Quinton 

The ground on this orchard is dry and hard. Dead tree leaves crunch beneath my feet. And it's January, shortly after four atmospheric rivers pummeled California. Nick Edsall says on this portion of the orchard water doesn't seep into the soil.

 

Nick Edsall 

The water runs to the end of the field and pools and puddles and it eventually either runs into a drain or it sits on the field for you know, multiple days to weeks and you'll see standing water.

 

Amy Quinton 

But not too far away in the same orchard. It's a different story. Knee-high green grasses and radishes flourish between the rows of trees. These are winter cover crops.

 

Nick Edsall 

This is a big radish right here. Look at that.

 

Amy Quinton 

Nick pulls up a daikon radish. The biggest I've ever seen. It looks like a giant white carrot, the width of a softball.

 

Nick Edsall 

And it's supposed to open up pores in the soil, so it's doing his job.

 

Amy Quinton 

Those giant pores allow water from rains to seep into the ground and help recharge the aquifer beneath the field. ºÙºÙÊÓƵ Agricultural Water Center Director Isaya Kisekka says cover crops improve that infiltration.

 

Isaya Kisekka 

If you have cover crops like this, you're going to improve soil structure, which is going to improve water holding capacity. But also by covering the soil you're going to protect the soil aggregates. If you don't have cover crops, the rainfall or sprinkler irrigation breaks up the aggregates, seals the soil and then water runs off.

 

Amy Quinton 

Cover crops grow on half of the 5000 acres of orchards on Bullseye farms. Nick says he planted cover crops several years ago to fix a high magnesium problem that was causing the soil to crack. Nuts that fell in the cracks couldn't be harvested.

 

Nick Edsall 

There's no cover here. You can see the cracking.

 

Amy Quinton 

Since then he's seen other benefits. The cover crops are attracting pollinators, preventing weed growth and water evaporation. Nick reaches down to show me the soil under the cover crop.

 

Nick Edsall 

You see the difference right there just from this being covered.

 

Amy Quinton 

It's dark, wet and healthy. And that means it's holding water, which helps replenish the soil under the entire orchard.

 

Nick Edsall 

I think because of the deep rooting and the soil cover, I think we're actually having to use less water to irrigate our trees than we normally would.

 

Amy Quinton 

But growing cover crops like any additional crop requires more labor. And Nick says Not every farmer is convinced of their value.

 

Nick Edsall 

Cover crops have their own water requirement. And there's a lot of growers that are hesitant to plant cover crops because they believe that it's going to be using up that precious resource.

 

Amy Quinton 

Nick hopes ºÙºÙÊÓƵ researchers can provide some solid data to see if cover crops use less water in the long run. And if they have other big payoffs, increasing soil moisture and health, recharging groundwater and even storing carbon in the soil. Matt Roby is a USDA research scientist collaborating with Isaya to find out. He stands next to a tall thin metal tower that hovers over the pistachio trees.

 

Matt Roby 

It's called a flux tower. And what it does is it measures the breathing of the biosphere. It measures the breathing of the agricultural system.

 

Amy Quinton 

He uses a handcrank to tilt the tower down so we can get a closer look at the instruments at the top. He says these instruments measure evapotranspiration or how much water is lost from the landscape to a thirsty atmosphere. The towers also measure the carbon dioxide exchange of the ecosystem.

 

Matt Roby 

What the instruments are doing is they're scanning really rapidly, the air and kind of sniffing the air for water vapor and carbon dioxide. And based on those changes in the gases, we can determine on average, if there's carbon that's being either emitted or released from the landscape, and how much water is being released into the atmosphere.

 

Amy Quinton 

Farms typically emit more greenhouse gases than they store. But these cover crops could put a dent in that by sequestering carbon. Isaya is using other high-tech equipment, including satellites, to look at soil moisture and groundwater. He says the satellite images of Nick's orchard after a recent rainstorm show promise.

 

Isaya Kisekka 

we take those images and do some computations to estimate soil moisture and they could see a very clear difference in soil moisture between the blocks in this orchard data cover cropped and the block of the orchard that are not cover crops so we see benefits there as well.

 

Amy Quinton 

Isaya says they want to improve satellite algorithms so water managers can make measure water use more accurately in California. Scientists will monitor these orchards over several years, both dry years and wet to understand changes in water use and groundwater recharge as the trees mature.

 

Isaya Kisekka 

The challenges are great, but also the advances in science and technology make me hopeful that we can continue to produce nutritious food that we all need, while making sure we're creating minimum impacts on the environment.

 

Amy Quinton 

By the way, Kat, you can go to our website and find links to some of those satellite images and you can really see the difference.

 

Kat Kerlin 

Are there drawbacks to planting them?

 

Amy Quinton 

Well, Isaya says the crops may be a great water conservation strategy where Bullseye Farms is located, but may not be everywhere.

 

Isaya Kisekka 

If you are in the Sacramento Valley where we receive on average 17 to 18 inches of rainfall a year, we can successfully grow cover crops without increasing our water demand, primarily depending on rainfall to do that. Now, if you're in southern San Joaquin, in Bakersfield, where you get maybe three inches of rainfall, then you have to think about twice about how that would impact your water balance.

 

Kat Kerlin 

So it's very site specific.

 

Amy Quinton 

Everything is very site specific, right? I learned that even within an orchard you can have some trees that need more water fertilizer than others.

 

Kat Kerlin 

But we know there are still other benefits from using cover crops that you mentioned, including attracting pollinators, building healthier soils and potentially storing carbon.

 

Amy Quinton 

Yeah. And speaking of healthier soils, I spoke with one of our Cooperative Extension assistant professors Mallika Nocco. You may also know her from her Water Talk podcast. She's researching a newer and potentially better cover crop.

 

Mallika 

It's been engineered for places like California where it doesn't need that much water and it's not going to compete with a cash crop for water. So it's a perennial cover crop. So it's more intended for, you know, orchard systems, perennial cropping systems. And it takes very little water to germinate. And we're starting to really understand exactly how much it does need. But it's a great example of like a new solution for how our cover crop could work in a more arid climate.

 

Kat Kerlin 

And what's the name of this magical cover crop?

 

Amy Quinton 

Oakville bluegrass. It's a perennial that could last 10 years. And it's dormant in the summer so theoretically wouldn't compete for water with other crops.

 

Kat Kerlin 

But of course, there's not just one solution to growing food with less water.

 

Amy Quinton 

Yeah, in fact, I also went to an almond orchard and Yolo County where they're using a really new technology and also an older one to conserve water.

 

Amy Quinton 

ºÙºÙÊÓƵ plant scientist Patrick Brown is walking down rows of almond trees at Westwind Farms. It's early February and warm. The trees in this orchard are just beginning to bud which worries owner Kirk Pumphrey.

 

Kirk Pumphrey 

Little early.

 

Patrick Brown 

Season starts already.

 

Kirk Pumphrey 

Yeah,

 

Patrick Brown 

Hope we don't get any frost.

 

Kirk Pumphrey 

Boy, don't say that word.

 

Patrick Brown 

You can see the little pink tips coming out. If we had this weather for a week, they'd be blooming.

 

Amy Quinton 

Early blooms worry every almond farmer. And it's happening more often as warming weather from climate change stimulates blooms. The earlier they bloom the more likely winter frost will damage almonds. Warming temperatures also mean thirstier trees, but Kirk has managed to use less groundwater despite drought conditions last year.

 

Kirk Pumphrey 

This past year, we saved of total water volume, it's just right at 5% over the previous years.

 

Amy Quinton 

He's done that in part by using a type of precision irrigation called pulse irrigation. Sophisticated sensors know when the trees need little pulses of water, just enough to replace water lost the previous day.

 

Kirk Pumphrey 

It's the difference between drinking from a firehose or here's a glass of water.

 

Amy Quinton 

He's pulse irrigating all 160 acres of almonds daily, instead of irrigating them twice a week. Patrick Brown says it's a simple concept. Just feed the trees when the trees need it.

 

Patrick Brown 

And the analogy is, you know, if you had a flock of sheep or a pig farm, you wouldn't put all the food and all the water down at the beginning of the year and hope it was there at the end. You feed according to the hunger and trees are not any different. So if you have the capacity to pulse the irrigation every day or even less than every day, depending on the demand of the tree,  then you can control and prevent losses.

 

Amy Quinton 

Another technique to quench the trees thirst requires no water. It's mulch which Kirk says every almond farmer has at their disposal.

 

Kirk Pumphrey 

It's the wholesome shell. This is a mixture of the soft hull and the hard hull from processing. And this mixture, its economic value is very low.

 

Amy Quinton 

Most growers sell it to feed cows because it's full of potassium. By putting it on the ground, Patrick says it's feeding the trees.

 

Patrick Brown 

The hull and the shell of almond, which is not the piece you eat, contains about 50% of the fertilizer demand each year. So if you return it to the orchard, then you don't need to put that much fertilizer on. And it also has benefits for organic matter in the soil. And it can save water.

 

Amy Quinton 

Kirk kicks over the top layer of mulch under his trees to reveal dark, moist soil underneath,

 

Kirk Pumphrey 

What it's really done is stopped the surface evaporation. You can come out here on 110 degree day and do the same thing. It'll look just like that. The top will be dry. But you get beyond that top layer. You've got it. It's there.

 

Amy Quinton 

It's also kept out the weeds eliminating the need for herbicide. So with all the advantages, why don't all growers use mulch? Patrick says it has to do with the traditional way growers harvest almonds.

 

Patrick Brown 

Which is you grab the tree, you shake the tree, you drop all the nuts on the ground, and then you sweep it up. Now if you're using that process, and there's residue on the soil, then it contaminates the nuts. So that's why we haven't done it.

 

Amy Quinton 

But Patrick is working on another project here to harvest almonds so they don't fall on the orchard floor. A new off ground harvesting machine like this one catches the nuts and recycles the hulls on the orchard floor. The only catch, farmers must buy the new equipment.

 

Patrick Brown 

It takes time. Every change in agriculture takes time. It does take new machines. And there's been some of the big buyers of almonds, who are starting to ask growers to adapt that new technologies so that the product they have can be claimed to be more sustainable and green and environmentally sound.

 

Kat Kerlin 

These new technologies and practices seem great for reducing water use, but I keep thinking of the 2600 basketballs per person analogy. I mean, is it really enough to make up for all that water we're drawing out of our aquifers?

 

Amy Quinton 

Well, you know think about it. Farmers have made some enormous changes in the last few decades they used to flood the entire field. Now most use more efficient drip irrigation or micro sprinklers. But doing that has also decreased the amount of water that percolates into aquifers.

 

Kat Kerlin 

Speaking of flood irrigation makes me think of all of these atmospheric rivers we've had. I know ºÙºÙÊÓƵ is researching ways to capture more of that water and spread it across farm fields.

 

Amy Quinton 

Yeah, the idea is that this could happen in winter months when crops aren't growing or when orchards are dormant. They could also capture it and store it underground. There's a name for it. It's called a managed aquifer recharge. hydrologist Thomas Harter, who is also working with our Agricultural Water Center says we'll need land and lots of it to do that.

 

Thomas Harter 

We're also thinking about how can we use agricultural landscape hundreds of thousands, perhaps millions of acres? Some places will be able to do a lot of water in a short period of time. Some places will be doing some water over large landscapes, and thereby also being able to squirrel away a lot of water into subsurface storage.

 

Kat Kerlin 

It's always harder than it sounds. Not all soil will allow water to seep into the aquifer. And diverting water from rivers or creeks means dealing with water rights issues.

 

Amy Quinton 

Yeah, Thomas told me that for the most overpumped basins, like those in the San Joaquin Valley, managed aquifer recharge might eventually recover 20 to 40% of the groundwater lost every year. Farms and communities will still need to use less. But Thomas says he's hopeful California can achieve sustainable water use.

 

Thomas Harter 

I'm optimistic that we will eventually figure out how to do this for our own livelihood. We have to keep water levels stable. We can't afford the amount of land subsidence that we've seen in the past.

 

Kat Kerlin 

We also can't afford to stop growing food. California is the most productive agricultural state in the nation.

 

Amy Quinton 

And Isaya Kisekka says it's easy to think about the water we drink, but we also need to think about the water we eat.

 

Isaya Kisekka 

We cannot have food without water. And managing water in agriculture is very important for our survival as human beings on this planet.

 

Kat Kerlin 

I can't top that.

 

Amy Quinton 

I know, right? I guess it's the perfect time to bounce now.

 

Kat Kerlin 

Is that how you're ending this episode of Unfold with the basketball metaphor?

 

Amy Quinton 

Well you know? I think we've bounced around enough ideas, don't you?

 

Kat Kerlin 

Yes, definitely. You can and learn more about the Agricultural Water Center at our website, ucdavis.edu/unfold. And check out all of our episodes of Unfold from previous seasons on food, climate change, health and curiosity. I'm Kat Kerlin.

 

Amy Quinton 

And I'm Amy Quinton. Thanks for listening.

 

Amy Quinton 

Unfold is a production of ºÙºÙÊÓƵ. It's edited by Marianne Russ Sharp, Original music for Unfold comes from Damien Verrett and Curtis Jerome Haynes. Additional music comes from Blue Dot Sessions.