usually get our water from some kind of centralized public system.

而我們這些生活在城市地區的人

Operating a water system is a major responsibility that has implications for public health and

通常會從某種公共儲水系統中獲取水

safety.

維持供水系統是一項重大責任 這影響大眾的健康與

In dense urban areas, a clean and abundant supply of water is an absolute necessity,

安全

not just for drinking, but also for sanitation and firefighting.

在人口密集的城區，乾淨與充足食水供應是必要的

And it's not just something we need every so often; water is a constant necessity both

不僅是為了日常飲用需要，也是為了衛生 和消防系統的需要

day and night, on weekends, holidays, and any time in between.

而且這不僅僅是我們經常需要的東西; 水是無論白天和黑夜，週末，假日

So, the job of finding enough water, making it safe to use, and then reliably distributing

任何時間也需要持續供應的東西

it to the system customers with almost no downtime is a monumental task that requires

所以，採集足夠的水，使水能被安全地使用 然後輸送到目的地

a lot of infrastructure.

而中間沒有任何停機的時間 是一項需要很多基礎設施

And probably the most visible component of a public water system is the elevated storage

的重大任務

tank, also known as a water tower.

或者最明顯的基礎設施組成部分 就是供水系統的空中水庫

I'm Grady and this is Public Works, my video series on infrastructure and the humanmade

又稱水塔

world around us.

我是Grady，這是Public Works，這系列的短片 是關於基礎設施

[This video is sponsored by Bombas.

以及我們世界周圍的人造建築。

More on that later.]

此短片由Bombas贊助

Let's say you're the owner of a public water system.

稍後再詳述。

You've found a source of water of sufficient quantity for your customers, you've found

假設您是供水系統管理者

a way to clean that water so it's safe for them to use, and now it's time to send the

你為用水的人們找到了豐富的水源

water on its way.

以及一種清潔食水的方法，因此水可以被安全地使用，現在是時候輸送水

There are a few ways we can get water from one place to another.

到目的地了

One of them is just to carry it there.

我們可以通過幾種方式將水 從一個地方運到另一個地方

Whether it's on the back of an animal, on a truck, or a bottle in your backpack, we

其中一個就是用容器將水帶到那裡

still physically carry water all the time.

無論是放在動物的背上，還是在卡車上 或是放在你背包裡的一個瓶子裡

But it's usually not the most efficient way.

仍然是物理上一直運送著水。

The first infrastructure dedicated to water conveyance was the open channel.

但這通常不是最有效率的辦法。

Whether in a ditch, canal, or aqueduct, the water is carried by gravity, sometimes over

第一個用於運送水的基礎設施 是明渠

very long distances.

無論是在溝渠，運河還是水道 水是由重力攜帶的，有時會將水運送一段

We still use open channels to carry water for irrigation and drainage, but they have

很長的距離

some disadvantages as well.

時至今日我們仍然使用明渠來運送水 來灌溉和排水

The water is exposed to pollution and contamination, channels bisect the land, making it difficult

但明渠的一些缺點到今天也沒變

to get across, and the water can only flow to areas of lower elevation than where it

水暴露在受污染和有害的環境， 水道也難以穿過土地

started.

水只能一直向海拔低於原來的地方流動

And that last one is a big disadvantage, especially if you're trying to deliver water to an

最後一個是很大的缺點 特別是難以想將水運到

area with hills or mountains.

山區或山上

So most public water systems today rely on pipes for distribution.

所以今天大多數供水系統都依賴於 管道來分配

Simply putting a top on an open channel allows us to take advantage of pressure to move fluids

只需在開放的頂部封上 即可利用壓力來移動液體

where we want them to go.

到水該去的地方

Just like electrons in a wire flow from high to low voltage, a fluid in a pipe will flow

像電子會從高電壓流向 相對低電壓的方向，管道中的液體將從高壓區流動到低壓區

from high to lower pressure.

所以，如果你在管道的其中一端加壓 ，你可以把你的水送到你希望它去

So, if you raise the pressure at one end of a pipe, you can send your clean water to anywhere

的方向

you want it to go.

要如何提高水壓？

And how do you raise the pressure of water?

用泵

With a pump.

泵是一種移動液體的裝置

A pump is a device that moves fluids.

在某些情況下，泵會將液體輸向到更高的高度

In some cases a pump literally lifts the fluid to a higher elevation, but in most cases a

但在大多數情況下泵是透過增加水壓來傳遞能量到液體中

pump imparts energy to a fluid by raising its pressure.

而泵，特別是那些為整個城市服務的大小的泵 造價昂貴

And pumps, especially the size of pumps that serve entire cities, are expensive.

所以，如果你的職責是為供水系統選擇泵的尺寸

So if you're tasked with choosing the size of the pump you need for your public water

你做什麼？

system, what do you do?

也許你需要測量城市在某一天的用水量

Maybe you measure the amount of water that the city uses in a given day and select a

並選擇一個匹配的泵可以應付該城市的用水量

pump that can match that flow rate.

讓我們看看它是如何運作的

Let's see how that would work.

這是你所在城市的午夜，大部分使用者在這時間都睡著了

It's midnight in your city and most of your water customers are asleep.

除了那些7/24的工業用水，水的需求量很小

Besides the industrial customers that run 24/7, water demands are minimal, and your

泵沒有遇到麻煩

pump is having no trouble meeting them.

但在早上5點左右，自動灑水系統 開始運作。

But around 5 am, automated sprinkler systems start kicking in.

早上6點左右，人們開始醒來，開始淋浴，刷牙，煮早餐

Around 6 am, people start waking up, taking showers, brushing their teeth, cooking breakfast,

所有活動都需要用水。

all things that require water.

用水需求不用多久就會超過泵所提供的量

It doesn't take long before the water demand exceeds the capacity of your pump.

在很短時間內，你的新泵就不能 滿足整個供水系統的需求

Almost right off the bat, your new pump can't meet your system demand, because it was only

因為它的尺寸只適合用水量的平均水平

sized for the average.

大城市地區的用水需求在正常的一天內，可能會有很大差異

Water demand in large urban areas can vary significantly over the course of a normal

高峰時每小時的需求（通常 在早上或晚上）

day, with the peak hourly demand (usually in the morning or evening) sometimes being

有時候高達每日需求平均值的5倍

as much as 5 times the average daily demand.

所以，如果你想只用泵來滿足使用者 用水量

So, if you are trying to meet your customer's water needs using just pumps, instead of just

你不只需要一個泵，你可能需要多達五個泵

one, you might need as many as five pumps (or one huge pump that can do the work of

或一個可以完成5個泵工作量的巨型泵

5).

不僅如此，你還必須反複 打開關閉泵以滿足用水量的變化

And not only that, you'll have to be constantly cycling the pumps on and off to meet the variable

這會增加設備的磨損

demand, increasing the wear and tear on your equipment.

而這就是存儲容器的來歷

And here is where storage comes in.

讓我們在系統中添加一個水塔後 再試一次這個實驗

Let's add a water tower to the system and try this experiment again.

現在是午夜，需求很低 但你的泵正在全開

It's midnight and demand is low, but your pump is running full wide open.

水不是流動到的使用者，而是 流入你的水塔，緩慢地

Instead of water flowing customers, it's flowing into your water tower, filling the

填滿了水塔

tank slowly but surely.

到早上，用水需求開始增加 你的泵仍繼續運轉

As morning comes and demand starts to increase, your pump continues running.

雖然它自身供水量無法滿足城市需求

It's not able to meet the demand on its own, but the stored water in the tank is making

但水塔儲存的水正令情況有所差異

up the difference.

你的使用者都獲得他們需要的水

All your customers are getting the water they need.

隨著人們開始新的一天，用水需求再次下降 低於平均值

As people start their day, demand again drops below average.

但是，泵保持運作，而額外的 流進了水塔水箱

But, the pump keeps running and the extra flow goes into the tank.

然後居民的需求再次開始飆升 他們開始做飯，洗澡

Demand again begins to spike as the residents of the city start cooking dinner, taking baths,

給植物澆水

and watering the plants.

所有這些額外的水再次從水箱排空

All this extra water use drains the tank again before most people go to bed and the cycle

在大多數人上床睡覺之前，循環再次開始

starts again.

很容易看出存儲空間是如何令供水系統更有效率

It's pretty easy to see how storage makes your water system more efficient.

它平衡了用水量的高峰與低谷 不僅僅是你城市的泵

It smooths out the peaks and valleys of water demand not just on your pumps but all your

而是所有在這個泵上游的基礎設施，包括水處理廠和水源供應的泵

upstream infrastructure, including your water treatment plant and raw water supply.

沒有存儲空間，所有這些設施都會 需要根據峰值需求進行調整

Without storage, all those facilities would need to be sized for peak demand, increasing

增加他們的成本

their cost.

有足夠的存儲空間，泵和其他基礎設施 可以根據平均需求進行調整

With enough storage, pumps and other infrastructure can be sized for average demands, saving not

不只是節省成本，但也簡化了程序，因為你不必預測需求的變化

only cost, but also complexity, because you don't have to predict changes in demand

並根據變化作出調整

and respond accordingly.

有時那些用量的高峰和低谷是可預測的 但有時不能

Sometimes those peaks and valleys are predictable, but sometimes they're not.

城市中一些最大的用水需求 來自於應對火災

Some of the biggest water demands in urban areas are from fires.

沒有消防部隊和足夠的水供應 火災可能在密集的城市地區失控

Without a firefighting force and enough water to supply them, fires can burn out of control

事實上，許多歷史上最致命的災難

in dense urban areas.

是火災發生的城市沒有先進的供水系統

In fact, many of the deadliest disasters in history were fires in cities before modern

現在大多數城市和建築法規

water systems.

對為消防用的供水量設立了最低要求

Now most municipalities and building codes have minimum requirements for the amount of

而擁有事先儲存準備好的水，像是儲存在一座水塔裡

water that must be available to firefighters.

令應對緊急情況時走了一大步。

And having water stored and ready, like in a water tower, goes a long way to being able

你可能會想，拜託Grady。

to respond to an emergency.

這不是什麼新鮮事

You may thinking, c'mon Grady.

儲存是古老的解決辦法 應付任何供應與需求不匹配的地方

This is nothing new.

而且，把水儲存在一個大水箱裡可能並不是什麼了不起的事

Storage is the age-old solution to any situation where the supply doesn't match the demand.

但水塔不只是大水箱 他們是位於高地上的大水箱

And, yeah, it might not be anything remarkable to store water in a big tank.

因為水塔不只是儲水 他們同時也在存放著能源

But water towers aren't just big tanks, they're big tanks elevated above the ground.

供水系統依賴於水壓 去令水流動到某處去

And that's because water towers aren't just storing water; they're also storing

如果你曾經用過低壓水淋浴 你會知道它有多麼令人沮喪的事

energy.

因為你無法獲得足夠的水

Water distribution systems rely on pressure to get the water where it's going.

為供水系統加壓也是對公共衛生很重要的

If you've ever taken a shower with low water pressure, you know how frustrating it can

管道內沒有足夠的水壓 污染物可以通過水龍頭或小洩漏進入系統

be, because you just can't get enough water out of tap.

大多數供水系統都會從泵獲得水壓

Pressurizing a water system is also important for public health.

而這需要很多能量維持水壓

Without enough pressure in the pipes, contaminants could make their way into the system through

所以，不僅是能存儲水本身

taps or small leaks.

能取代泵賦予能量也是很重要

Most water systems get their pressure from pumps, and it takes a lot of energy to maintain

在某些地區，電費會根據需求有所不同

this pressure.

您可以在晚間電費很便宜的時候，發動泵來填滿你的水塔。

So, having the ability to store not only the water itself, but also the energy that has

然後，在白天電費更貴的時候將泵關閉

been imparted to it by the pumps is important.

只使用水塔去加壓供水系統來服務你的用戶

In some areas, where electricity costs vary based on demand, you can run the pumps at

在更大的規模以這種方式存儲能量 還可以提高電網可靠性

night when electricity is cheap to fill up your water tower.

但這會是另一部影片說明的另一個主題

Then, leave the pumps off during the day when electricity is more expensive, allowing just

高架存儲同時有利於停電時 通過位能保持系統加壓

the tower to pressurize the system and serve your customers.

即使泵停止運作

Storing energy this way is also carried out at a larger scale to help with electrical

但他們需要多高？

grid reliability, but that's a topic for another video.

你可能已經知道一個水壓與水的深度有關

Elevated storage is also beneficial during a power outage, by keeping the system pressurized

你越深，水壓就越大

even when pumps are out of service.

就像在游泳池或海洋中

But how elevated do they need to be?

供水系統在深度和壓力之間也有相同的關係

You might know that the pressure within a body of water is related to the depth.

只是水被限制在一系列管道之中

The deeper you go, the greater the pressure.

所以，你可以想像一個供水系統 就像我們生活在一個虛擬海洋

Just like in a pool or the ocean, a water distribution system has the same relationship

高架儲存水箱的水面 就代表虛擬海洋的水面

between depth and pressure.

以這種方式想像一個水系統 很容易看到供水系統在

It just happens to be confined within a series of pipes.

給用戶帶來合適的水壓時將會有所挑戰

So, you can imagine a water distribution system as a virtual ocean under which we all live,

如果我們的城市是平的 那就非常簡單了

and the water surface in elevated storage tanks represents the surface of the virtual

所有在虛擬海洋上的建築 都坐落在同一深度

ocean.

但大多數地區至少也會有 一些地形起伏

Imagining a water system this way makes it easy to see the challenge of delivering water

低海拔用戶位處於虛擬海洋的底部 水壓太高了

to customers at the right pressure.

你可能認為這是件好事 但是垂直管道及器械只能

If our cities were flat, this would be pretty simple.

承受某程度的壓力，超過這些等級時 會造成嚴重的損害

All the buildings would sit at the same depth in the virtual ocean.

有時低海拔的建築會 配備特殊的閥門以減少壓力

But most areas have at least some amount of topographic relief.

高海拔的客戶非常近虛擬海洋的表面 水壓非常低

Customers at low elevations are at the bottom of the virtual ocean, where pressures can

正如我之前所提及，低水壓不僅令人沮喪 也會導致供水系統的污染

be too high.

為了解決這個挑戰，許多大城市 分隔了供水系統，稱為壓力區

You might think this is a good thing, but plumbing pipes and appliances are only rated

每個壓力區都有自己的水塔 為城市內不同海拔的用戶供水

to certain pressures, so exceeding those ratings can cause serious damage.

但是，如果您需要為在同一地點 但不同高度的用戶供水，會發生什麼事情?

Sometimes buildings at low elevations will be equipped with special valves to reduce

高層建築，如摩天大樓，會有足夠的水壓給下層用戶

the pressure.

而有些較高的樓層卻會 靠近虛擬海洋靠近表面，甚至在這之上

Customers at high elevations will be near the surface of the virtual ocean, having very

因此，大多數高層建築不是依靠城市提供水壓 而是使用自己的泵來為上層供水

low water pressure.

有些城市，比如紐約，甚至要求 每棟建築都有自己的高架存儲空間

As I mentioned, this can be not only frustrating, but also lead to contamination of the system.

不是每個城市都使用水塔

To solve this challenge, many large cities maintain separate distribution systems called

有些地方的水源位於更高海拔 最大限度地減少了增加壓力到系統的需要

pressure zones, each with their own water tower, to serve customers at different elevations

有時候只依靠泵來保持供水系統運作會更合理

within the city.

畢竟，水塔並不便宜 而且佔用相當多的空間

But, what happens if you need to serve customers at different elevations in the same location?

一旦沒有足夠循環 水塔會讓水停滯

Tall buildings, like skyscrapers, can have adequate water pressure on the lower floors,

但供水系統的關鍵是可靠性

while the higher floors can go up near the surface or even above the virtual ocean in

高架水箱絕對會以某種形式或方式 保留下來的

the water distribution system.

感謝您的收看，留言讓我知道 您的想法

So, instead of relying on city water pressure, most tall buildings use their own pumps to

感謝Bombas支持Practical Engineering

provide water to the upper floors.

再次，謝謝你的收看，讓我知道你的想法

And some cities, like New York, even require that each building have its own elevated storage

tank.

Not every city uses water towers.

Some have their entire water supply at a higher elevation, minimizing the need to add pressure

to the system.

And, sometimes it just makes more sense to rely on pumps alone to keep the system up

and running.

After all, water towers aren't cheap, they take up quite a bit of space, and they can

allow water to stagnate if it isn't circulated enough.

But, with public water supplies, reliability is key.

And, it's been a long time since gravity was knocked offline from a thunderstorm, so

elevated storage tanks (in some form or fashion) are definitely here to stay.

Thank you for watching, and let me know what you think!

Thanks to Bombas for supporting Practical Engineering.

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Again, thank you for watching, and let me know what you think!