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Case-lesson “Water – simple and complicated”
Case-lesson “Water – simple and complicated”

Category: Science, nature and human

Level (grade): 6+

Subject: Natural phenomena

Objective: To discover what properties and peculiarities make water an irreplaceable natural resource of modernity and why.

What information is waiting for me here?

  • Does the world have enough freshwater for its needs? Where are the greatest and the least amounts of freshwater located?
  • What kinds of cities can be built on water?
  • How does water come into our houses?
  • What fundamental and practical knowledge will I need?
  • How is cost of water calculated?
6 scans of the subjects, phenomena and practices:

Can you imagine the world without water? It would have been an endless dull lifeless desert. Water is an inseparable part of the world, its foundation, without which the existence itself is impossible.

Despite being so ordinary and familiar, it still keeps a lot of secrets. Water gives an impetus to development and improvement of not only nature but our civilization as well. Let’s unveil some of these mysteries.

According to various assessments, a human body consists of 70-90% of water. 75% of our planet’s surface also consists of water (it is not clear then why it is called Earth, rather than Water).



How much water at all is it on Earth? And what portion of it is potable? Which country is the most stocked with fresh water, and which is the most arid? Let’s answer to these questions using geographical knowledge.


What components form freshwater resources?


How are these resources distributed among different countries?


So, what country is the most “arid”? The answer is Libya. 99% of this country’s territory is a desert. If we tried to draw up a “rating” of aridity, the leaders would look like this:


The rating of the most stocked with water countries is the following:


Water availability and water resources are dynamic parameters. Water resources can be depleted not only quantitatively but also qualitatively. Water pollution makes it unfit not only for drinking but also for industrial and agricultural applications.


What rivers flow in your city? Do they have a special feature that distinguishes them from other water objects? Do you think this water is suitable for usage and if yes, for what exactly? And what kind of water tastes better: from well, from tap or bottled?


Human, like virtually all life on Earth, needs water. In the past people just used to settle where they could find sources of surface water (lakes, rivers, streams) or places where surface water flowed from underground sources, forming springs.

Approximately 7000 years ago human learned to dig wells and moved from nomadic to settled life. The possibility to irrigate land gave a push to the development of agriculture, farming and culture in general. For instance, the well, found by German archaeologists in 2005 (fully excavated in 2010) dates back to the age of 7000 years:


Reconnaissance of water sources became an important job. Some looked for water by watching birds and animals, some used vine for the same purpose.

World of the Ancient East has given mankind new types of wells, suitable for irrigation and drinking. Egypt was the birthplace of a crane well, which at that time was called “shadoof”. Every innovation in the “water field” was the result of scientific and technological progress, and, at the same time, a stimulus for the further development of the civilization. For example, shadoof creation required understanding of principles of operation of a lever:


Without sophisticated irrigation and water supply systems it would have been impossible for one of the Wonders of the World – the Hanging Gardens of Babylon to appear. Here’s one of the attempts of their virtual reconstruction:


The Indians had been using stepwells – “baoli”. They’d collected rain water. The depth of such wells could reach 3500 steps. To estimate the required size of the well it was important to understand how to calculate volume:


In the ancient times the construction of any inhabited locality began with building a well. Culture has given the world the first plumbing – aqueduct. It was built of limestone; the height of the construction could reach up to 10 m. Aqueducts have been known from the VII century. Ancient aqueducts used the gravity flow water principle, which was based on the filigree usage of natural elevation range. Even the modern version of hydraulic calculations is quite difficult for this phenomenon:


Watermills have been known since the II century BC. However, they became the most widespread in the Middle Ages period. During this period, each Catholic monastery was ordered to acquire such mill. The very use of the water wheel – a primitive turbine – involves understanding of the correlation of work and power, kinetic and potential energy, even though in different terms and without a formular rationale. And modern physics has described it with a formula of the well-known phenomenon and explained it using the law of conservation of energy:


Water mill is a hydrotechnical facility that uses water power, obtained from a water wheel. Water wheel movement performs useful work through gearing. This principle is applied these days as well:

Relatively simple medieval water wheels have “grown” to the hydroelectric power stations of nowadays’. They’ve exactly become the essence of the previous experiences of aqueducts and water wheels, shadoofs and baoli:


But the relationships between mankind and water have been developing not only in the direction of water energy usage. Water itself has become a resource: a resource for technology and industries. With upgrading and development of technology the importance of water, as a resource, has only intensified. But water quality has come to the forefront: the fewer impurities are in it, the better “raw material” it is. Water is not only a reagent and a solvent; it is also an “environment” for many reactions and processes.


Another aspect of this relationship between water and human is a medical one. And not only because of the fact that water is a raw material for pharmaceutical manufacturing. As soon as people realized that part of horrible infectious diseases could be transmitted through water (e.g., cholera, which has killed hundreds of thousands of people), hygiene and sanitation, as branches of science, have immediately started to develop.

The social and political meaning of water, the awareness of its importance, its global value for the mankind came only in the twentieth century. The proof of it is the World’s Freshwater Map.


This new phase has spawned new techniques of sea water desalination and transporting icebergs, as well as hydroponics, projects of “water” cities, fuel production based on water.

Water in the modern world has become a source of inspiration for creative people, giving the world new forms of art on the brink of sculpture, painting and technology.


The idea of cities and villages “on water” is not new. And although Venice is usually associated with it in the first place, people settle on water in different parts of the world. Let’s “travell” to these cities and villages, and take a look on what these cities can be transformed into in the nearest future.


Giethoorn is a village in the province of Overijssel in the Netherlands. It is located in the community Stenveykerland, 5 km southwest of Steenwijk. It is known as Venice of the North or the Dutch Venice. Most of the buildings are built on islands and are connected by wooden bridges. There are 2620 residents in Giethoorn, whose houses are connected by 50 bridges. The depth of the channels between houses is about 1m.


Venice, which has already become a common noun, is the Italian city with an ancient history, permeated with channels and connected by a cobweb of bridges. Launches, boats, historic gondolas and an analogue of urban buses - floating vaporetto - connect various parts of the city, located on the islands or the mainland. This city is one of the most popular tourist centers, which has got its status rightfully.



"Floating" cities and villages can be found in Thailand, China, Myanmar and Vietnam. Usually, buildings there are constructed on stilts, so the water level changes don’t affect the building itself. Many residents find their jobs in spheres, connected with fishing or tourism. Gradually, the correlation between these two areas of human activity in towns like this is changing in favor of tourism.

Example: a floating village Ha Long Bay (Vietnam).


Population is only 600 people, mostly fishermen families.

Chinese town Zhouzhuang is usually called Venice of the East. This is a well preserved historic floating town, permeated with channels and connected by stone bridges. Zhouzhuang is one of the Chinese tourist centers.


Kampong Ayer is city in Brunei. Its name translates as “water village”, but the city has “outgrown” the status of village ─ it has population of about 39,000 people. And although the city is already 1300 years old, it is quite a modern place with all signs of contemporaneity (the Internet, gas stations, air conditioning, satellite TV, etc.), which are masterfully “masked” by the historical appearance of the city.



Ganvie town with a population of 20,000 is called the Venice of Africa. Tourists enjoy this African pearl that combines the exotics of unusual buildings and African coloring.


Latin America

Uru are floating island-villages in Bolivia and Peru. The population consists mainly of uru (Uros) people, who had historically lived on the costs and floating islands of Lake Titicaca. Once those islands had had a defensive purpose, these days – tourist. The peculiarity of the islands is that they are made of cane.


Palm (Dubai)

Dubai is a wonderful place in the middle of desert, where the achievements of scientific and technological progress of the XXI century have intertwined with an ancient culture. One of the most ambitious projects of the UAE is building of artificial islands. The Palm Jumeirah is the smallest and most original of the three islands. This is the first palm island and a great achievement in the history of world architecture. The size of the island is 5x5 kilometers and with a total area of more than 800 football fields. The island is connected with the mainland by a 300-meter bridge and the crescent is connected with the tip of the palm by an underwater tunnel. The estimated cost of Palm Jumeirah is approximately 14 billion dollars.


Archipelago World

Archipelago World is an artificial archipelago that consists of several islands, whose overall shape resembles the continents of Earth (hence the name – “World”). It lies 4 kilometers away from the Dubai's coastline. Artificial islands of the Archipelago World have been created mainly of sand of Dubai shallow coastal waters. The sand’s been scooped from the bottom of the Persian Gulf and then sprayed above the building site, to create the islands. The total area of the Archipelago World is 55 km2, what makes it the largest artificial archipelago in the world. “World” is connected with the mainland solely by water and air communications.



One of the concepts of cities of the future is a floating “lily city” Lilypad. The idea of cities like this belongs to Vincent Callebaut. Suchlike city-island can accommodate 50,000 people. The city looks like a lily with three petals, “growing” around a central lagoon. Owing to its specific flora and fauna, the central lagoon collects and purifies rainwater. The three petals provide a space for work, recreation and infrastructure of the city. They also become the basis for the hanging gardens and vertical planting of greenery that forms a “natural” city border. The living quarters are located not only in the petals, but in the underwater part of the “lily” as well.


Such lily-city is able to solve the problem of overpopulation and lack of residential areas under conditions of melting glaciers and the raising level of the world's waters. The implementation of this architectural concept can become nearly the biggest architectural breakthrough of the twenty-first century.


Would you like to live in a floating city? What are pros and cons of that? Suggest what other “floating” houses or cities could be built in the future?


Water is a “highway” for water transport traffic. Still water doesn’t affect the speed of a ship, boat or swimmer. But water current is able to change the speed sufficiently. You have probably paid attention to the following effect: if to try and swim against the river’s stream, it blows you away, hinders you. So, what is the mathematical solution of the problem of velocity in a moving water stream?


Let’s imagine that the river stream’s speed is 2 km/h. The speed of a swimmer athlete is 6 km/h (let’s consider a trained athlete as an example). The speed of a rowing boat is 2.5 km/h. The distance between the swimmer and the boat is 17 km. How long will it take before the swimmer and the boat will meet?

So, the swimmer is going with the flow, and it helps him. Therefore, his speed will be added to the flow’s speed: 6 + 2 = 8 km/h.

The boat is going against the flow, thus, the flow makes its speed decrease: 2.5 – 2 = 0.5 km/h.

In one hour the swimmer and the boat will overcome this distance: 8 + 0.5 = 8.5 km/h

If the distance between them is 17 km, then they will meet in: 17 / 8.5 = 2 hours.

So, what distance each of them has overcome so far?

In two hours the athlete has swum 8 * 2 = 16 km.

And the boat has overcome only 0.5 * 2 = 1 km.

The flow stream can be a helper and as well as an interfering factor. It is necessary to take this into account, not only when solving mathematical problems, but also when assessing your strength before swimming.

The problem:

How would the time in which the swimmer and the boat have met have changed, if the boat had gone with the flow and the swimmer ─ against it?


Have you ever thought about the way water come into our houses? If it is water from a borehole then the answer is obvious. But what if it’s tap-water?

Water is pumped from underground or surface sources, then it is submitted to a water treatment plant, where it goes through many stages of purification, and after that it is delivered to your house via a plumbing system.

This is a centralized water supply system. Contingently, it can be depicted in the following way:


If water is supplied to your house from an individual well, it is a decentralized (decentralized or local) water supply:


So, what are the methods of water intake? Here are some of the examples, which illustrate the fact that water can be taken from different depths. Herewith, the chances of water contamination, and therefore the quality, will vary.


Type of water supply, depth and water intake method will affect not only its quality but price also. The more complicated the scheme of water supply is and the deeper a borehole is located, the higher the price per liter will be.

Hence water saving is not only a question of preserving one of the most valuable resources, but also a question of financial economy. For example, in England it is accepted to close an outlet of a sink with a plug and before doing washing up and not to use hot and cold water mixers (only separate taps). It is due to high prices for water in England. And what other methods of water saving are out there?



How does water come into your house? What do you, which one of the water supply methods it is?


Water is priceless. But at the same time there is a fee for water supply, and bottled water even have a well-defined prices. Where do these numbers come from? Let’s examine different methods of water intake and distribution.

Tap water is water of centralized water supply. What is its price formed of?


But tap water doesn’t always keep up with a quality, required by consumers. Not only does it spoil the taste of food and drinks, cooked with the use of it, but it also has a negative impact on human’s health. This is why the quality of water is brought to fit the norm by means of special devices. In general, they are called filters, though their functioning is based on different principles: self filtration, ion-exchange, osmosis, ozonation, electrochemical cleaning, etc. If to clean only the portion of water that will be used for drinking and cooking, the cost of water will emerge from the following expenses:


If tap water contains rust, if it is "hard" (there are lot of mineral impurities, forming scum or sludge), it is harmful not only for humans but also for household technology which uses it: dishwashers and washing machines, coffee machines, water heaters and others.

Then all water coming into house, apartment or porch is cleaned. To accomplish this, people use more powerful devices with a higher resource and margin of safety. Their price will also differ from the price of an ordinary household filter. Expediency of their application depends on how "polluted" the water source is and what volumes of it should be cleaned. Then the cost of water will be the following:


In some cases, centralized water supply system is absent. Then water from wells or boreholes is used. How is its cost formed?


Some consumers buy clean water for drinking instead of using water purifiers. The cost of such water consists of the following:


There are a few ways of how the cost of water is formed. By realizing what volume and quality of water is needed, it is possible to “influence” the “water charges”. In addition, water, as well as many other resources, requires thrifty and reasonable use. This saves not only the resource itself, but bankroll to pay for it.

The task: Track how much and what type of water you family uses in a week. What portion is used for drinking and what for other purposes? Do you use water treatment devices? Think about how you can influence the cost of water for your family, is it possible to “redistribute” it, to reduce the cost?

Lesson summary:


The contents


The results of the case-lesson can be complemented with findings of students



What three websites helped find important information?


https://ru.wikipedia.org/wiki/%D0%93%D0%B8%D0%B3%D0%B8%D0%B5%D0%BD%D0%B0 http://www.vodainfo.com/ru/about_water/types_water/hardsoft_water.html


To help student and couch:





Where can you get information for the case?











Location of the lesson:

The case-lesson takes place in the classroom.

It is possible to hold the lesson at museum or library.



Teams of boys and girls.

The score was:


1. Which team will give more names of rivers, lakes, swamps and water reservoirs?

2. How would the time to meeting change, if the distance between the swimmer and the boat had was 34 km, the speed of the boat was 5 km/h, and the speed of the swimmer was 3 km/h?






90 min (double lesson)



The possibility to conduct the lesson with a student-understudy:



The acquired knowledge and developed competence:

Knowledge about peculiarities of freshwater distribution in the hydrosphere

Knowledge about the history of global resources of water development and contemporary problems in this area

Modern and perspective water architecture

Acquired practical skills in calculation the movement on water with considering the current

Receiving concrete geographical, historical, economical and other knowledge (given in the scans).



freshwater, lakes, rivers, underground waters, swamps, glaciers, water availability, stream speed, water intake, water clarification, plumbing, borehole, water wheel, well.



 Hrabowska Larysa


Participated in the case upgrading:



The End

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