How Watersheds Work | Stuff You Should Know Podcast (Transcript)
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Length: 32 mins
Unless you happen to be standing on a hilltop or swimming in the ocean right now, you are on a watershed. These unsung wonders of topography and hydrology are an important contributor to the rain cycle and yet we humans tend to abuse them.
Welcome to Stuff You Should Know, from howstuffworks.com.
Josh Clark: Hey and welcome to the podcast. I'm Josh Clark and there's Charles W. Chuck Bryant and there is guest producer Noel, who frankly, I think he's done enough times that we should just be like, "Our other producer, Noel."
Charles W. Chuck Bryant: Yeah.
JC: And then, if we were in France, I'd say, "Our other produc‚àö¬©r, No‚àö¬©le."
CB: [Laughs] So just removing the interim tag, the guest tag?
JC: I think he's, I think he's earned it. Don't you?
CB: Yeah. What is with you and these snacks?
CB: All right everyone, you should know Josh has a largish cupÔøΩ
JC: This is not large! It's a small tumbler at best.
CB: A tumbler full of jelly beans and animal crackers, as if you are a 4-year-old.
JC: 4-year-olds should not be eating this, though.
CB: [Laughs] Weird. I don't like jelly beans, though.
JC: Well, whatever.
CB: Do you put them in your mouth at the same time? Is that the idea? Because they're all just mixed in there together.
JC: Yeah, I, I guess, I meanÔøΩ
CB: Really? You're eating the animal cracker at the same time as the jelly bean?
JC: Oh, oh, no, no.
CB: Oh, okay.
JC: No, I see what you mean. I thought you meant the different flavors of jelly beans.
CB: Oh, gotcha. Are those weird jelly beans or, like, "Hey, this is fart, this is snake oil."
JC: [Laughs] Yeah. They're not supposed to be though, I think they turned.
CB: [Laughs] Yeah, it was supposed to be just lime and grape.
JC: [Laughs] Right. Snake oil. That's a good, good one.
CB: Uh, so I've been singing the Indigo Girls song in my head all day because of watersheds. Just want to throw that out there.
JC: Is that one of their songs? I knew it was one of their restaurants.
JC: I didn't know it was named after a song.
CB: Yeah, "Up on the watershed," is how it goes.
JC: Yeah, it's a good restaurant. It's Emily, from Indigo Girls?
CB: It was, I'm, I'm not sure if it still is, but yeah.
JC: I think it still is. Well, so she named Watershed after her song.
JC: But she named a song after the actual hydrological unit of watersheds?
CB: Yeah, I think she thought that naming a song, um, Kid Fears would be weird.
JC: Oh, is that the song?
CB: [Chuckles] No. Watershed is the song, but I was just making a joke about another one of their songs.
JC: Oh, okay. I thought maybeÔøΩ Yeah. This is the most confusing Indigo Girls conversation I've ever had.
CB: [Laughs] Including the famous, uh, Indigo Girls conversation of ÔøΩ03?
CB: This is, what? More confusing?
JC: This is the worst, the worst intro we've ever had in our lives.
CB: All right. Well, let's continue then.
JC: All right. So, Chuck, umÔøΩ
CB: With watershed.
JC: Well, I already kind of gave it away a little bit by saying it's a hydrological unit.
JC: Okay. So a watershed is basicallyÔøΩ Actually, it's even easier to say what's not a watershed.
JC: Not a watershed is a ridgeline or a hilltop or a large body of water, like a lake or an ocean or a bay.
JC: Everything else is basically a watershed.
CB: Yeah. Which is, to say, a place where watersheds. [Laughs] Rainwater, water comes down upon the earth and then eventually finds its way to a larger body of water via watersheds.
JC: That's right.
CB: Uh, I just saw that there was this cool thing, I can't remember the exact name of it, but a thing you can do here in Georgia, where you can follow the water from Atlanta all the way to Sapelo Island.
JC: Oh, that's neat.
CB: Uh, and it's a tour. I think you, like, canoe part of it and you just sort of, you know, follow its path. It's like a little eco trip.
JC: Oh, I see. I thought you meant, like, online.
CB: No, no, no. You actually do it.
CB: Like, uh, forget it. [Laughs]
JC: No, it does sound pretty cool.
CB: Yeah, it's neat.
JC: I saw somewhere that, um, one drop of water, this is on a kids website, but one drop of water stays in a lake for about 100 years.
JC: Before it moves along.
CB: Is that why you're eating the jelly beans and animal crackers?
JC: What? Oh, because I was on a kids website? Yeah.
CB: Nice. All right, so we know what watersheds are and are not. Uh, if you want the strict definition from the EPA, they said, "It's any body of land that flows downhill onto a waterway."
JC: Yeah, so they can be very big, they can be very small. I saw somewhere that made reference to something the size of a footprint could conceivably constitute a, a watershed.
CB: I saw that too.
JC: Right? So, basically, anything that's defined by some sort of higher elevation, um, that moves water, that moves water on a downward slope.
JC: Toward some sort of flowing water that goes into a larger body of water. Again, that's a watershed; you put these things together and one little watershed that feeds water to a tiny little trickling stream that, uh, leads to a larger stream that leads to a river, that's one little watershed, but it's a part of the larger watershed for that one big river.
JC: That that little stream feeding it is just one of many streams feeding it, and each of those streams has its own little watershed. So it's a weird little patchwork quilt or jigsaw puzzle that overlays any bit of land.
JC: Um, those are all watersheds. And when you put them all together, they all form one cohesive whole, and the boundaries are defined by elevation.
JC: Because if you, as this article puts it, if you live on a, a ridge, uh, and your neighbor lives on the other side of the ridge, you live in two different watersheds.
CB: And you're mortal enemies. [Chuckles]
JC: Right, exactly. You're a Hatfield and you're a McCoy.
CB: Uh, that, the, our own article, um, had a nice analogy with the umbrellas, like, if you turn over, let's say 5 or 6 umbrellas at varying heights on top of one another and they all had holes at the bottomÔøΩ
CB: Any water, let's say it started raining, it would just collect various different parts of the umbrella and it would all flow down and eventually exit that bottom and maybe go into another umbrella.
CB: But that would eventually, eventually get down to that main umbrella which would be whatever main body of water it flows into.
JC: Right. SoÔøΩ
CB: An ocean or, or a lake or whatever.
JC: Yeah, and then each, each, uh, watershed is defined by the, um, the headwater of the water it goes into.
JC: Right? So, um, theÔøΩ Well, you have three things as far as flowing water goes, right? You've got the headwater.
JC: Where, say, like, the river begins.
JC: And snowmelt and rain all flows downhill to this thing to form the beginning of the river, and there it goes, there it's off.
CB: Yep, headwater's release.
JC: And then, um, when that flowing water hits another, uh, stream of some sort, you've got a confluence.
CB: Yeah, those are great.
JC: Confluence. And then, um, where they end, say, like, they go into a bay or something like that, big river empties out, like the Mississippi.
JC: Empties into the Gulf of Mexico. Where it empties into the Gulf of Mexico, that's the mouth.
CB: That's right.
JC: And all this water, it moves downhill or uphill, it moves toward the equator. The bulge in the earth attracts the water like crazy.
CB: Yeah, It can't move uphill, though, can it?
JC: Uh, to us, we would think it was uphill because we're looking down, onto the southern hemisphere.
JC: For the southern hemisphere, it'd be downhill to them. It's just wacky.
CB: [Chuckles] I will say though, one time I was in a rainstorm in the desert that was so bad that there was water running uphill briefly.
CB: It was freaky looking.
JC: I'll bet.
CB: Like, it's just something your brain doesn't know how to process. When you see a definite grade in the land and water going the way that it shouldn't be going, I don't know what caused it. Or maybe it was the drugs? [Laughs] Just kidding. Um, it was an intense storm. And the desert storms, actually this lead right into this part nicely, desert storms are amazing because of how the water runs off compared to what I was used to growing up in the southeast. But, um, there are, uh, a lot of different things that can happen to the water once it rains or once that snow melts. It's not gonna all end up in the mighty Mississipp or that ocean.
CB: And here they are.
JC: Yeah, there's a lot of stuff that can happen to it along the way.
CB: That's right. Uh, infiltration is one of the big ones. Uh, the rain falls on the dry ground, obviously. Water is gonna soak in, get into that soil or infiltrate it. Uh, some of it will remain there in that shallow, uh, layer. Um, and then that's gonna move downhill, through that soil still, um, into, let's say, an aquifer or something.
JC: Okay. Yeah, that, that's, um, infiltration, right?
CB: Yeah. And sometimes it goes a long way, uh, or remains stored for a long period of time before it comes back to the surface, sometimes it doesn't.
CB: But it's just how much is infiltrating the ground.
JC: Yeah, and those, um, underwater rivers are pretty interesting. You've got ones that are, like, in a karst system, like a limestone system, where it actually is, like, a river underground.
CB: It's amazing.
JC: Like a cave.
JC: But you also have underground rivers, um, that aren't part of karst systems and that are actually rivers underneath rivers, right? So you have a river bed.
JC: All of the sediment and soil and dirt, and, uh, sand and gravel that make up a river bed is porous, but it's also saturated, which is why there's a river on top of it.
JC: But because that river bed is porous, water actually flows through it as well.
JC: So that's one of the other ways that water can kind of flow invisibly to us, underneath a river through the ground.
CB: Yeah and, and that infiltration, and how that water flows, it depends a lot on the soil characteristics whether or not it's clay or sandy, like you were saying. And then also, like you mentioned, it's just like a sponge, that soil saturationÔøΩ
CB: You know, can only get so saturated, and then you get that lovely river.
CB: Uh, and then, of course, the land cover has a big impact too. Um, if you've got, you know, what humans have done is created a lot of, uh, they paved paradise and put up a parking lot. [Laughs] You don't like that song? [Laughs] Really? All right. Um, you seem shy about admitting that.
JC: Oh, I don't like to put things down, you know?
CB: Oh, okay. You don't want to yuck a yum. Um, I do like that song, though.
JC: That's great.
CB: Um, so anyway, what we've done is we've paved a lot of things and then that creates what's called the fast lane for rainfall, and that is, it's not the only reason why, but that's one of the big reasons why we have floods, is that this water that normally would take a more lazy route and a more natural route.
JC: Yeah, water is super lazy.
CB: Um, if it hits that pavement and all, then you, you get water running much faster and in ways you maybe didn't predict.
JC: Yeah, the geological service calls impermeable services "A fast lane for rainwater," storm water.
CB: Fast lane.
JC: And it is true, and the built environment definitely alters the way water moves through it.
JC: Um, so human, not just human, uh, intervention or obstruction, but also human use too, like when we draw water out of an aquifer.
JC: That prevents it from, ultimately, going to its destination or delays it I should say, depending on what we do with that water.
JC: Like, if we drink it, tinkle it out into a stream, we actually make it go there faster.
CB: Are you encouraging that?
JC: Nothing wrong with that, man.
CB: [Laughs] All right. Well, let's take a quick break and we'll talk a little bit more about some of the other, uh, things that can happen to water once it hits the ground.
CB: All right. So, um, we teased everyone that other things can happen to water. It can turn into wine.
JC: [Chuckles] Yeah, right?
CB: If you believe the Bible.
JC: It can evaporate and then turn into rain for the rain cycle.
CB: Yeah. Well, that's a big one. Um, did we do one on evaporation or just clouds? That's probably where we covered that one.
CB: Fluffy clouds or something.
JC: Little Fluffy Clouds is a good Orb song.
CB: Uh, but when rainfall does, uh, come down to the ground, a lot of it does, go back up in the atmosphere through evaporation and that depends on, uh, how hot it is, the temperature, uh, wind, atmospheric pressure, lot of other things.
CB: Uh, then there's also transpiration.
JC: This is my favorite.
CB: Is it?
CB: Well, take it away.
JC: Yeah, well, basically, when you have plants, they're also taking in water themselves, putting it to good use.
JC: Breaking it down, creating chlorophyll, not borophyll, chlorophyll, uh, and just generally making things pretty and happy. That's transpiration.
CB: Yeah, and that'll slow the runoff, obviously.
CB: Because, taking a more circuitous route.
JC: Well, locks it up. And then eventually, it should evaporate from the water or from the plants and enter the rain cycle again.
CB: Yeah. And then, of course, other man-made things like water storage, like, you know, if you build a dam or something, you're literally in control of the release of that water.
JC: Yeah, that's a huge threat to the, um, health and vitality of wetlands, is dam building. Like, it helps us.
JC: You know, we have, um, basically a huge store of drinking water that we can create electricity from, but for the downstream ecosystems it's, dams are not good.
JC: Plus, they can cause earthquakes, if you remember correctly.
CB: Uh, yes, that's right. I remember that.
JC: You remember?
CB: Uh-huh. Uh, soÔøΩ
JC: Hold on. I have to say it, I was thinking the other day about those shorts. For the uninitiated, we used to do one-minute shorts that appeared on The Science Channel. They were, like, that precursor to our, um, actual show.
JC: Do you remember those shorts?
CB: Sure. Yeah, they were fun.
JC: So, theÔøΩ I thought of one the other day. Remember the one where we're playing racquetball? That was, I think, the pinnacle of all of them.
CB: Just the setup?
JC: Yeah, just the whole thing, everything went, it, it was just perfect. I just thought it was great. It just popped in my head the other day and I was like, "I totally forgot we even did those things." And then, I was thinking about it and thought it was hilarious.
CB: Yeah, the gag on that one was that I was wearing, like, a full, like, basketball uniform and sweat band.
CB: And goggles. And you were wearing, like, an Oxford and jeans.
CB: And we were playing racquetball.
JC: That was it.
CB: Like, how funny was that? [Laughs]
JC: Yeah, I, I just thought it was great.
CB: I'm surprised that never took off.
JC: Well, it did. It got us a TV show.
CB: Yeah, that's true. We did, likeÔøΩ
JC: It was the TV show they didn't take off.
CB: We had a couple dozen of those shorts, right? Those were all fun. I'm gonna start posting some of those again.
JC: Well, this is my passive-aggressive way of asking you to.
CB: [Laughs] Okay. Uh, so watersheds areÔøΩ Keeping them clean is a big deal. Um, it really matters because there's a domino effect that can happen.
CB: Um, when they're polluted.
JC: Oh, yeah. So water is great for transporting things, right? We put barges on them, jet skis on them, sailboats.
JC: It's also really good for transporting other stuff, like anything that's a pollutant is really easily moved along through water, right?
JC: And the whole point of the watershed is moving water across land into larger bodies of water. Well, the stuff that's in the way of that water gets picked up and carried in along with it too, right?
JC: So the pollutants that we just leave lying around, everything from dog poop to, um, antifreeze ends up in the, the water.
JC: Because it's in the watershed, so it ends up in the body of water. And since we use these, the, these bodies of water for all sorts of different things, it's a big problem and, and it's a, it's a, it's something that, I think more people need to be aware of. Because you thinkÔøΩ
JC: "Yeah, I'll just leave my dog poop there on the ground."
JC: You don't think about how it's going to rain, and flush that dog poop in there.
JC: And create a, uh, coliform bacteria bloom.
JC: That's going to kill a bunch of fish or give them salmonella.
CB: Yeah, it seems certain cities, on their stormdrains, have little signs that say things like, you know, just reminders of, like, you know, "What goes in this thingÔøΩ"
CB: Uh, "will end up in, you know, some larger body of water."
CB: "And have a big impact."
JC: Yeah, that's good stuff.
CB: Uh, I found a thing that said the leading cause of pollution are sediments and a lot of times, bacteria, like E. coli.
JC: Right, from dog poop.
CB: Yeah, and even excess nutrients can be bad.
JC: Yeah, because those form algae blooms, right?
JC: So algae blooms are, um, where a, a type of algae is already present in a body of water.
JC: But then, all of a sudden, there's a bunch of agricultural runoff, say. So there's a huge introduction of nitrogen and phosphorus, which are fertilizers.
JC: Well, algae is a plant and algae blooms as a result. And they can block sunlight for other plants in the, in the body of water. Um, when they die off, the bacteria that eats them and, or decomposes them uses up tons of oxygen so it chokes the life out of the fish that are in the body of water.
JC: Um, it can make things quite smelly.
JC: It's, it's just not good for anybody. And, and the reason why these algae blooms happen is because of the fertilizer runoff.
JC: That's being introduced into the bodies of water.
CB: All right. Well, let's take another break and, um, more, more depressing news right after this. [Chuckles]
JC: All right, Charles, where's the, where's the silver lining here?
CB: Well, we're gonna hear some more bad news.
JC: [Laughs] Okay. I was hoping to change that.
CB: In the United States, 40% to 50% of our waters are impaired or threatened.
CB: And impaired means that it doesn't support, uh, one or more of its intended uses.
JC: Impaired means it's drunk.
CB: [Chuckles] It is.
JC: It's drunk likeÔøΩ
CB: Drunk with pollution.
CB: Uh, so one or more of its intended uses could mean you can't swim in it, you can't drink it, um, don'tÔøΩ You know what's always scary is like, "Yeah, it's good fishing over there. Just don't eat them."
CB: That's always, like, "Oh, wow."
JC: Yeah, and thenÔøΩ
CB: "That bad."
JC: But it could be, it could be anything, it could be from, there's high levels of mercury in there to, you know, there's, um, toxins or, um, I'm sorry, bacteria.
JC: That can kill you. Flesh-eating bacteria lives in bodies of water.
JC: There's a lot of reasons and a lot of, a lot of stuff you just take, "Oh, well, that's the, that's the natural state of thatÔøΩ
JC: "Body of water." That's absolutely not true.
CB: Yeah, and, like, you know, you're pointing out here that it's all, it's all interconnected. The EPA has a paper called Sustaining Healthy Freshwater Ecosystems, and they really try to drive home the point that these are not isolated bodies of water.
CB: Like it's, it's all very much tightly linked to one another and, uh, the human impact has this domino effect that, you know, you throw that cigarette out of your car and you don't think it's a big deal, that's gonna end up either in a bird's nest or a body of water. Just two places. [Laughs]
JC: Right. Can't you see a little baby bird being like, "What is that? Why did you bring that home?"
CB: Just nuzzling up.
JC: [Chuckles] Right.
CB: Against it. Rubbing its little baby bird head. Uh, where else? Around the world, this is, obviously, a big problem; it's not just the United States.
CB: Uh, in the Amazon Basin, and the Amazon River dolphin is threatened with extinction because of the domino effect of, uh, watershed runoff pollution.
JC: Well, you said it earlier, you said human, human activity, basically.
JC: And it's not just us polluting, like, say, you pour out your antifreeze and just go in, yuck into yourself about how great that was.
JC: Kicking the antifreeze over.
CB: "I had to change my oil. I just dumped it down the storm drain."
JC: Yeah, you're not supposed to do that. That's not good, right?
CB: Not good.
JC: It, it goes beyond that. Like our activity, like, say, um, if you tear up some trees along a stream bed.
JC: Well, tree roots have a really great effect of holding soil in place.
JC: And without the roots to hold that soil in place as the stream passes by and maybe floods a little bit after a big rainfall, it takes a lot of sediment with it.
JC: Well, you say, "So long, riverbank, who cares?" That sediment can go clog the gills of fish downstream.
JC: And kill them. All because you just couldn't live with the tree in your backyard.
CB: Yeah, or because you just had to build your river house that you visit three times a year. [Chuckles]
JC: But even still, even if you did build that, you would want to keep a buffer of treesÔøΩ
JC: Along the riverbank.
JC: Like, there's just some steps you want to take, right? And it's, it's easy to overlook a lot of the activity that we do, um, that has these, these negative effects on, on water bodies because we're doing them elsewhere but in the watershed that's still connected to the body of water.
JC: I don't know if we've driven that home enough yet.
JC: That the activities we do on the watershed affect the bodies of water in the end.
CB: That's right. Uh, but people are taking action. Um, the first Watershed Protection and Flood Prevention Act came about 1954. That was a little bit more about coordinating, uh, flood efforts or flood prevention efforts rather.
CB: Uh, and then in 1972, they added some more conservation efforts to that. And then in 1996, they, um, I think they made it friendlier to get loans for groups carrying out measures that would help promote watershed management.
CB: Financial loans.