The Simple Genius of NYC’s Water Supply System 

I am a scientist that works for the DEP for the catskill Delaware system. You managed to pack in years of knowledge and understanding of our water system in 16 min. Great job! I should have new hires watch this video.

I’m a pilot and last week I flew into White Plains, right over the Kensico Reservoir for Runway 16. It was a gorgeous summer evening and all I could imagine was paddle boarding on the beautiful lake I was flying over. I noticed that there was no traffic on the water and no houses on the shore which seemed strange given the lake’s proximity to a huge population center. Later I figured it had to be part of the city’s water supply to enjoy such a lack of disturbance and I got to thinking about what goes into keeping NYC hydrated. This video had perfect timing to my logistical ponderings. Thanks for some more outstanding material.

Hey there, I used to work on the Kensico Reservoir in 2018-2022 as contractors for NYCDEP for the Waterfowl Management Program. Our job was to deter ducks and gulls from sitting on the reservoir and dropping their waste into the city's water by constantly scaring them away throughout the year. It was a cool job and the reservoirs are beautiful. Nice video!

I'm actually hoping when they finally bring tunnel 1 offline we get some photos of what it looks like on the inside. No one's been in there for over 100 years, they found out in the 50's the sectioning valves were inoperable, so they couldn't even shut sections off for maintenance. As it is right now, if a major failure happened in tunnel 1 or 2 it would be a huge disaster for the city, the capacity just isn't there until tunnel 3 is fully operational.

these videos never cease to interest me, as someone who isn’t really that much of a nerd. Sam never fails to make me interested in whatever topic. Thank you Sam!

I grew up with the Croton River Reservoir systems in my everyday background in Putnam County NY and was always in awe when I was told that (most) bodies of water I saw everyday were the Citys water supply. Most of my summers were spent hiking and fishing in NYC DEC controlled areas. Winters were spent walking on the ice watching the icefishers. The Citys land ownership has made the county artificially rural. This video spoke to me personally as I have spent time at almost everyplace you have shown. My great great grandfather emigrated from Italy to work on the New Croton Dam. This system and the infrastructure in it helped spark my interest in engineering at a really young age, and I went to college in the Catskill region near Kingston NY. This is also the most concise yet detailed explanation of the system I have found that taught me a few things I didn't even know despite having seen this entire system in the background of my life. Well done.

Living in NYC, I am hugely grateful to the brilliant people who provide millions and millions of people with fresh, clean water every single day. 🙏

Honestly, the fact that this single city has constructed all this show just how incredibly powerful and influential New York is

Man i wish this Half as Interesting guy made videos of this quality. You have no competition from him!

I was an intern in a chem lab in NYC's DEP chem lab one college during summer, measuring fertilizer and coliform concentrations. They knew it was a pretty boring internship so they tried to attract interns with weekly field trips (on paid time! Well, it was minimum wage...) to various water things... we got to go INTO the old croton aqueduct in Ossining. It's super cool.

I live right next to the Ashokan Reservoir. Been studying the NYC water system for years. I love going out into the woods to find all the century old engineering like the aqueduct.

My dad worked at the Tarrytown water treatment plant all my life (and way before i was born) and it’s so cool to hear you talk about Croton because my dad would have to go cover there every once in a while. I remember going to the water treatment plants after school and just drawing, coloring, seeing giant tanks, all just because I was waiting for my dad to finish working so we could go home lol. Also really cool to hear some of the towns I grew up in/near in this video :)

Back when I did an architectural thesis focusing on the pollution in the hudson river, you touched on basically everything for the the NYC water supply, but a topic idea for the future could be looking at combined sewer systems and seperate sewer systems. The hudson river still has raw sewage dumped into it during heavy rainstorms due to the existing combined sewer systems in the towns and villages along the hudson river. Potential future video idea for ya

I love how Sam can correctly pronounce Poughkeepsie, but not potable.

I always love water infrastructure. Canals, aqueducts, dams, reservoirs, and the massive tunnels that go with them. It is absolutely impressive the scale of such objects. It is as frightening as it is beautiful.

I studied at Cornell University over a decade ago. I took a microbiology course and as a side project we looked at cryptosporidium parvum oocysts (ie. parasite eggs). These oocysts are spread by cattle manure and can contaminate drinking water causing diarrhoea. There was concern they could contaminate Catskill/Delaware aqueducts because there was runoff from surrounding dairy farms that drained into them.

As a water utility worker I find this fascinating. The idea of not needing to filter surface water is truly unique. We actually filter ours twice. The first stage is mechanical particle removal and the second is adsorption of organic material

Its really a modern engineering marvel to see such a mega design that serves millions even now. Wish we had similar level of foresight now for our modern problems that could serve future generations.

New York state in general has really good water throughout most of the more rural areas anyways. Where I grew up the water supply came from artesian wells and and was consistently rated as among the top 10 public water supplies in the country for purity.

I live about 1/2 a mile from the Ashokan reservoir. And what you said about DEP cops up here is no joke. They are everywhere as well as helicopters flying overhead. Especially in the warmer months. I’m a native New Yorker so I can see both points of New Yorkers and locals up here. The paranoia the city has about the water purity makes life for locals very frustrating. I always found it ironic that my water source is terrible well water. Un drinkable due to its nasty smell and taste. Yet right next to me is this huge water source that is untouchable for us locals.

When he said the physics of siphons was not fully understood, I had to remind myself that this was not Half as Interesting

Awesome video

The physics of the siphon are actually really well understood. Just based on pressure

As someone who has lived in Ny state on the Saw Mill pkwy, my local water quality rating always is in the top 10 of 150 counties around me, which always felt awesome, and as a Bike RIder I have driven through all of these reservoirs, in summers and during the fall, it is a very beautiful place to be, also my cousin had to do a project on the water system for the city, where I learnt all of this interesting stuff. It feels great hearing all the familiar places you have been to are actually a really big part of a larer system. Great video and really well made, now I am going to share this with all of my family.

When I lived in Long Island City, Queens, when I went to bed, I'd hear a very low humming sound. Then one day reading the paper it mentioned the digging of Water Tunnel #3 going under the East River several hundred feet below. I then realized the humming was not in my mind.

Currently reading Empire of Water by David Soll which focuses on the history of NYC’s water supply. This presentation is just as informative and the images are something that books just can’t replicate. Great work!

According to Food Theory (spinoff channel from Game Theory) New York's water has lower chlorine levels and higher fluoride levels than other places in the U.S., which allows yeast to do its job better and longer before the chlorine kills it off. That extra yeast time allows the pizza dough to stretch extra thin without breaking, and affects the flavor.

This is exhibit #1 in how NYC and NYS have a symbiotic relationship. Upstate supplies water to a city that could not exist without it, while NYC supplies NYS (as well as nearby states, and to a lesser degree the US), an economy and tax revenue stream it could not exist without. Peace - John

Interesting, I was just in New York yesterday and pondered this same exact question while overlooking the Hudson River - how such a massive population center surrounded by undrinkable water can support itself. I checked the maps and saw basically no substantial reservoirs nearby and no rivers besides the Hudson which, just by looking at it, definitely isn’t drinkable.

I love how Wendover calls the Tappan Zee Bridge what the locals call it instead of its actual name. No one calls it by its actual name, not even Wendover 😂

I love the word choices in your scripts Sam and Tristan (and whoever else was involved in writing this video)! Also thank you, as always, for providing many of the metric conversions of their imperial counterparts!

“The physics behind how siphons work is not fully understood..” -I LOVE learning the random things modern science STILL can’t actually explain. Like explaining how BICYCLES work is still a complete mystery in physics despite DECADES of research & experiments searching for an answer of HOW BICYCLES SELF-STABLIZE? It’s a mystery so beautifully humbling to hear.

its interesting that the next longest tunnel is for the Helsinki water supply which is a substantially smaller city and the tunnel is only about 10% shorter :D though the bedrock there is very stable so probably more afordable

I am SO glad Sam called it the Tappan Zee and not the “Mario Cuomo Bridge.” The majority of us locals have refused to accept the change

My city uses about 50 MGD ( million gallons per day) New York uses a billion? That blows my mind! Treating the wastewater would be another great video.

I did a laboratory installation at the Croton Reservoir intake structure back around 2000. The client, who knew of my interest in the site engineering, took us on a tour of the large mixing valves, designed to draw in different levels of water. Then, at a lower level, inside of a chain-link enclosure, he showed us a tall wooden box, maybe 3' x 3' x 6'. The outside was dark, crazed varnish with noticeable rusted piano hinges. He began to swing parts of it open, revealing an 1890s-era swing-away model of the then new aqueduct intake structure. It was exquisite, with railings about 1/2" high and the concrete funnel cast in plaster. There was a darkened bronze plaque on the inside honoring the commission that oversaw the aqueduct improvement. All of the names were Irish, naturally. This had been built to carry around to different investors and to show off the plans to the public. I don't know what has happened to the model. I hope that it is in good care.

I love how you used the term Tappan Zee bridge in the first minute of this.

As a New Yorker, being able to drink good tasting tap water is great. I recognize that not everyone has that privilege, so I am grateful for it. Also having lived in a place where I could basically see the Kensico Dam from my house, it's quite a sight. Not monstrously tall, but impressive nonetheless. And the little green at the base of the dam is a great place to relax.

I am a resident of NYC and have used the water here all my life. You managed to pack in years of knowledge and understanding of our water system in 16 min. Great job! I should have new residents watch this video.

That answered a lot of questions I had growing up in the Bronx. We also had small reservoirs inside the 5 boroughs. I lived by the one in the Bronx. They were always talking about building a water treatment plant on that spot to meet stringent federal water quality standardes. People outside of NYC are surprised when I tell them that NYC is actually award-winning. You can imagine we REALLY thought the idea of bottled water was ridiculous. I stopped drinking from the tap when I moved, even to upstate NY.

Seeing that they re-chlorinate the water at certain points puts the food theory video about the water being why NYC Pizza is so good into more perspective.

Thanks for using the former name of that bridge. It will always been the Tappan Zee

My home city of Helsinki in Finland has a similar, smaller scale solution (though large scale for a city of a mere million). Our water supply comes from Päijänne, the largest lake in the country. We use less than a hundredth of the supply it could provide. The water comes into the city along a 120km tunnel, and it is also used to drive turbines for power as the elevation difference is significant. It's weird to think about how my city has a hydro power plant, without the usual dam around.

2:40 I am Originally From there. Kingston NY. Born there until I moved away at 17. Kingston, NY to NYC took 90 mins as it was 90 miles away. Albany was 60 miles away so 60 mins it took. But I used to go Fishing at Ashokan Reservoir and even walked the Trail out there.

8:15 TIL "The physics of Syphons is not fully understood". Uhm looks pretty clear to me: Gravity and greater mass on one end. If downwards-facing, the longer leg contains more water which when falling pulls the water behind it. If upwards, the same, except the longer tube pushes down.

Fun fact: If the Sacandaga Reservoir wasn't built, then the Hudson River would flood and lead to the cities of Poughkeepsie and some parts of New York City being flooded.

I drive past the Ashokan reservoir all the time going skiing, and back home I’m around 3 miles from one of the more southernmost nyc reservoirs. Most of us in the area know some of this of this but it’s awesome to see such an in depth video on it. The DEP thing is serious, I have an access permit since you need it for a lot of hikes and mountain biking.

Beautiful job distilling such a fascinating topic into a concise 15 minute video. I’ve lived in NYC my whole life and only just found out that the longest tunnel in the world sits right in my backyard! Thank you for shining a light on this incredible system 👏🏼

He called it the Tappan Zee bridge, THANK YOU

Thank you for calling it the Tappan Zee. It's criminal that the best named roadway in the NYC area was renamed

I was 5 years old in 1960 when my family took its weekly car trip from Chenango County NY to Binghamton, to see my grandparents. From there we swung down to Deposit NY in Delaware County, to see my cousins. My Uncle told my parents about the work going on in nearby Cannonsville. The whole town was being destroyed while they built a dam on the creek there. So we drove over to Cannonsville. When we got out of the car, my father showed me the creek and said that all that water will eventually flood the entire Valley. He pointed out a farm up on the hill, saying that that farm would not have to be moved but everything below it would be covered with water in a few years. So the people had to move from this town. Across the street from us a woman stood on her porch roof with 2 workmen. The workmen wore pocketed canvas toolbelts and she was telling them how to preserve her stained glass windows on the upper floor. Next door a workcrew was crowbarring apart the roof and walls of a house. Dump trucks were on the street, slowly being filled with wood as the houses were demolished. I asked why they were destroying the houses and damming the water. My father explained. "Far away there's a big town. And the people there are thirsty. They need water. There are so many people in that town that there's not enough water for them nearby. So they're building a big tunnel to bring this water to them. The tunnel will have pumps inside that look like window fans. They don't want pieces of wood floating into those pumps because the pumps will stop , and the water won't get to the town. So the wooden houses are being taken apart to get all the wood out of the town before the flooding starts." There are around 8 million people in New York City. I'm probably the very last one who remembers Cannonsville before it became a reservoir. I think about it every time I take a drink of water.

I live near Kingston NY and walk around the Ashokan reservoir periodically. It's breathtaking!

The map visuals in this video were excellent, especially the 3D maps that show underground depth

Im from new york and when i was in elementary school we took part in a program that connected upstate schools and downstate schools to learn about the water program and connect the two. it was really cool because we got to go upstate to the reservoirs and do the filtration tests. the program was funded because there is some animosity because the city flooded multiple towns in the creation of the reservoir and many people here dont even know the history

My uncle Theodore Decker died while building the Delaware Aqueduct at Shaft 2A, in Kerhonkson, in February 1940. He was one of five that died that day. I live above that tunnel, shaft 2A, 1550 feet down. Shaft 2A was an after thought. All the shale by there was hauled up as tunnel muck. Both My father was a welder and my grandfather George Decker worked there. It was good pay.

Amazing how much work goes into providing a city with clean, drinkable water. Equally amazing how many people will pay 1000 percent more to drink basically the same product from a disposable plastic bottle.

I spent much of my childhood in the Catskills, especially by the Ashokan Reservoir. There are trails on the dams and dykes along the banks and on an old rail corridor that was until recently supposed to be restored as a tourist rail operation. Fishing is allowed, but only in flat bottom rowboats and you need a permit to go out. There’s a ton of wildlife in and around the reservoir as the Esopus Creek which feeds it is a trout stream. Various waterfowl can be found on and around it and there are at least three nesting pairs of bald eagles by the shores.

At 8:20 there is an error. The technical term for this phenomenon is communicating tubes. However, this only applies to static systems, not to dynamic systems. When water flows, it loses its energy through friction (head loss).

The world's longest tunnel before the Delaware Aquaduct was actually a 3000yr-old qanat in Iran stretching 71km, bringing water to the city of Zarch. Most Western media seems to be unaware of qanats; they're a mind-blowing ancient accomplishment that can hardly be matched today. The network of people who maintain them is disappearing, and they themselves are almost invisible, leading to widespread ignorance about them. For thousands of year, they've provided water and even in some cases a surprisingly sophisticated passive air conditioning system for many people, mostly in Middle-Eastern places.

What’s even more interesting is that the cities jurisdictions span even further beyond the reservoirs shown here. There are multiple sewage treatment plants in upstate New York that are owned and operated by NYC. Most of those plants discharge into the Esopus Creek, Neversink River, and Deleware River, downstream of where the water diversions are. So the actual span of the operation is even larger than we see here! It’s really amazing actually.

Many years ago, I remember the news program on ABC called "20/20" running a blind taste test where they pitted NYC's tap water against like 10 different brands of bottled water. From what I remember, the NYC tap water ended up getting second place. I guess I now know part of the reason why!

Thanks for calling it the Tappan Zee Bridge, though I don't know if that was on purpose, instead of the Governor Mario M. Cuomo Bridge. No one local calls it by that name because the State Capital took over naming it without any support from the locals of either county the bridge connects. There's been a political movement from both counties to have it rename to something that locals would agree on.

Excellent! Having grown up in and around NYC, it is true we were always proud of the great refreshing cold water we got from the tap. The research you have done on this is amazing! Well done.

An excellent portrayal of what it takes to provide potable water to a megacity! A follow up of this video, focusing on dealing with the downward outflow of a city's 'used' water, will assist residents of the value added, and problems faced, by their local City Engineer's Department! Well done.

Thank you for making a video on this topic. I’ve been acutely aware of the complexity of NYC’s water source since I learned that my great great grandfathers farm was purchased via eminent domain along with the whole town of Cannonsville. That town no longer exists , along with many other towns, as they were bought to flood for these reservoirs. The buildings and churches still exist under the reservoirs today. The only thing that was removed was graves.

Things YOU DIDN'T KNOW you need to know.

Wendover has confirmed that the bridge is in fact called the “Tappan Zee Bridge” I can now die happy

Thank you for the deepest dive on the origins of the water I spent nearly half my life drinking, washing and playing in. Like so may others things in the city it was something I completely took for granted.

The bypass tunnel and everything that's gone into it is probably one of the greatest engineering accomplishments of the modern era. Just to get done to the tunnels elevation, workers had to dig a 900 ft (275m) deep shaft, straight down through solid rock

I live right on the Croton Aqueduct in Westchester, and I run along it quite often. I gotta say, it's amazing what we have here in New York and thanks for helping explain it to all of us!

Love that nerve agent fluoride

Newark has an equally impressive aqueduct system linking the city to its multiple reservoirs in the hills & small mountains of New Jersey.

If you've never tasted NYC water, you are in for a treat when you do. It has a very clean taste, not unlike bottled water.

Yoooooo I wasn't expecting a hometown Poughkeepsie shout-out in this video! You nailed the pronunciation too

Wow! So informative and educational! Thank you! I really enjoyed watching this! Living now in NYC, it's good to know how important and crucial to have such good water to serve 9 million people!

An absolutely stellar video presentation of a stunningly large water system I didn't know about. Thank you!

I can't wait for Adam Something's video on this next week!

Awesome video. I like how this channel focuses on real, impressive feats of engineering like this, instead of fake "tech bro" pipe dreams like Hyperloop and SpinLaunch. I'd rather watch something like this than some CGI-inspired stupidity any day.

this was an amazing watch, it was highly intuitive and constantly had me pondering about factors throughout the video which then also get addressed

What competing theories are there for how siphons work? I thought that was pretty open and shut at this point. I mean its gravity, pressure, and flow rate. I'm legitimately curious.

Great work Sam. There is another key factor that contributes to the system, which is the PES (Payment for Ecosystem Services) program that provides alternative income for the land owners to protect the land (when private).

When I visited my friend in New York, I refilled my water bottle at his tap and immediately was concerned as the water was so cloudy I couldn't see through it. I asked him if he drank the tap water and he said of course. When I looked back at the bottle, the water was perfectly clear. It turns out that the pressure used to pump water up into skyscrapers forces air into the water. When it exits the tap, the air turns into millions of microscopic bubbles that gradually get bigger and exit the water as it reaches normal pressure. Really cool effect for someone who had never seen it.

Wonderful video. Thanks for sharing the knowledge

That was very well done.

Siphons are, in fact, quite well understood. It's simple physics... pressure.

I feel envious at the engineering achievements of both the water and subway system because I feel like I will not see any new developments in this lifetime. Everything is so profit driven that it doesn't matter the overall good it would contribute. It's just as necessary now as it was back then to maintain these marvels!

this video was incredible. have always wondered how this works and amazing to see the scale of what was built before.

that's all pretty amazing. great video. the simplicity and complexity all at the same time is fascinating

This was highly interesting. Y'all knocked another one out of the park, Sam and crew.

I live in White Plains right near Kensico and a friend of mine is an environmental scientist who works for a company that does a myriad of testing and surveys at the reservoir Kensico Dam Plaza is often used as an outdoor venue, which is always cool. EDIT: Always nice to find people who pronounce Poughkeepsie correctly. And thank you for still calling it the Tappan Zee.

I grew up near the Neversink reservoir, I always wondered how the water got to the city. This was very informative! Thx!

One of my favorite parts about my hometown will always be the Kensico Dam and how beautiful the reservoir looks in the fall.

A memo on the correct pronunciation of certain words: 1) the 'pot' in potable rhymes with boat and 2) alum has a 'short u' vowel sound (phonetic rules would usually create a 'long u' if the word ended with an 'e').

every time I learn something new about New York City and it's odd/ fairly unique infrastructure/ways of building things I and amazed by how it is nearly always equal parts genius and jank

The physics behind how siphons work is very well understood.

I designed water plants, did stormwater management studies for watersheds and, New York City's Water System is amazingly interesting.

Prague, the capital of Czech Republic has a very similar system. Water from the Švihov dam is transported to the water treatment plant in Prague via 52 km long tunnel using gravity only. Actually the sixth longest water tunnel in the world! But the scale of our system is nowhere near to the one of New York, astonishing!

Amazingly you can go fishing/boating on a lot of these reservoirs, even in sections of Kensico which holds some of the largest trout around New York City because of the deep cold water.

Astounding project and fantastic video!

Buried here below a golf course Is the most Westchester sentence you could’ve chosen 12:35