NCWR

About NCWR

Rainwater harvesting

In a nutshell

In this activity we become “hydraulic engineers” and see how a rainwater harvesting system operates.

45 min

10-13 years old

In class

Our objectives

In this activity you will:

  • Find out about the operating parts and functions of a rainwater harvesting system.
  • Learn how we can use the collected rainwater.
  • Consider possible applications of such a system in your home or school.

Stop and wonder

DISCUSS IN GROUPS


  1. Until recent years in various Mediterranean islands, many houses had their own rainwater harvesting . Why so? Why did they stop using them?
  2. Today, in several cities around the world, even in those where water is abundant, many new buildings are equipped with rainwater harvesting systems. Why so? Where do you think this water can be used ?
  3. All around the world, infrastructures like sport fields and airports are equipped with rainwater collection systems. Why so? How do they use the collected water?

Play & learn

Find the pot to collect the rain!

If you wished to collect the rainwater, what equipment would you use? Here are some ideas given by students!

 rainwater-harvesting quiz-hotspot
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Water-readings

The elements of a rainwater harvest system

For any rainwater harvesting system to operate there need to be certain provisions, including:

  • An, as wide as possible, catchment surface, on which the rain falls. This can be a roof, a terrace, etc.
  • A sieve (or net, e.g. like the windows sieve) to be placed at the opening of the gutter. This can act as a rough filter and keep out debris, leaves, pebbles etc. from the rainwater .
  • Gutter or drainage pipe is an open horizontal or closed vertical pipe through which the rainwater flows.
  • control valve to control the flow of water either to the tank or the yard.
  • A filter to further clean water from small sized solids, dust, etc.
  • A tank / cistern to store the water. This can be made of cement (built), plastic, or metal. It may stand freely on ground or be carved underground. In any case the users need to have access to it.
  • A pump and pipes to transfer the water.
  • An overflowing siphon that leads the excess water out of the tank.

The above system ensures water sufficiency to houses and is rather simple to construct and install, that is why it was so popular all around the Mediterranean for centuries. Modern installations at buildings can be much more sophisticated, but to a large extend their operation is based on the same principles.

Play & learn

The parts of rainwater harvest system

Based on what you have read so far, drag and drop the parts of the rainwater system to the right spot in the diagram.

 rainwater-harvesting quiz-hotspot
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  • 1 1 catchment surface
  • 2 2 sieve (filter)
  • 3 3 gutter / drainage pipe
  • 4 4 filter
  • 5 5 pump
  • 6 6 tank
  • 7 7 overflow siphon
  • 8 8 control valve

Stop and wonder

DISCUSS IN YOUR GROUPS


  1. Even when the tank is underground, why do we need to have access to its opening?
  2. During which season we need to clean the filter?
  3. The control valve gives us the option to choose whether to direct the rainwater inside the tank or not. In which cases the rainwater is not wanted?

 

Play & Learn

How do you think we can use the collected rainwater? We can use it for (choose the right options) ...

Rainwater is appropriate for watering our garden, flowers and vegetables.

This way we can achieve an important saving in our bill!

Rainwater can be drunk only after its disinfection, as it might contain microorganisms. Disinfection takes place using specific filters or chlorine or UV rays. In any case, before we drink it it is necessary to have it tested in a chemical lab.

Rainwater does not contain salts, thus, is proper for washings. Actually, certain washing machines have a "rain" operation mode. However, if we do not disinfect the water first, we should avoid using it in the washing machines..

Rainwater does not contain salts that is why women in the past, preferred it for washing their hair. Today, when installing a modern rainwater harvesting system we avoid bathing with it because we do not know if it contains microorganisms. It needs disinfection and lab test in order to use it for showering or drinking.

Rainwater can be used for such outdoor cleaning purposes

Activity

What do we gain by collecting rainwater?

  • We reduce the water bill.
  • We reduce the demand from the water supply network.
  • We reduce the risk of flooding, particularly in cases of large-scale structures (see Rainwater Harvesting in Practice).
  • We take advantage of a water of good quality, clean enough, that would otherwise be lost in the sea.

Apart from households and buildings, rainwater can be collected at large-scale installations and sites such as airports, fields, urban squares, valleys and slops, to be used for watering the urban green, irrigating the crops, etc.

How much rainwater can you collect at school?

If your school has a water tank, you can easily calculate how much rainwater it collects within a year. Even if there is no tank, you can still calculate how much rainwater could have been collected if you know:

  • The area of the catchment surface (in square meters ). This information can be obtained by the school director or you can calculate it after measuring the building’s perimeter.
  • The annual average rainfall of your area (in millimeters per year, mm/ yr).  You can find this in the website of the Meteorological Agency. Then, the amount of rainwater that can be collected in a year (in cubic meters, m3) is:
Area (m²) x Average annual precipitation (mm) x [runoff coefficient] *** = .... m3)
  • What is a run-off coefficient? During the system operation there are some losses e.g. due to evaporation or spills at the catchment surface.  So, we use a “run-off coefficient”, a number that expresses these losses and it depends on the material of the catchment surface. For instance, it is about 08-0.9 for metal; 0.75 to 0.9 for concrete surfaces; 0.8 – 0.85 for gravel; 0.5  for clay tiles, etc.

Water shares


Water meter

I liked this activity . . .

Way forward

Surfing around the internet

Watch here a short animation about the rainwater harvesting system that has been installed in a Primary School in Malta.

Dive in…

The water cycle in a bowl! if you want to  make rain through a model of the water cycle!

Rainwater Harvesting Systems in practice if you want to read more about a real installation of a rainwater harvesting system!

Go back to the homepage!

The water basins

Water in the city

Desalination

Do you know about grey water?

Rainwater harvesting

Greywater recycling in practice

Wastewater treatment

The water cycle in a bowl!

Waterworks through time

Climate change challenges

Rainwater Harvesting Systems in practice

Reduce-Reuse-Recycle

Water resources

Where do I begin?

The water basins

In this activity we learn what a water drainage basin is and why it is important for the experts to study it.

Continue!

Water in the city

What is the "urban water cycle"? Which are the important aspects of water management within a city environment?

Continue!

Desalination

Let's find out how sea and brackish water can become a freshwater resource!

Continue!

Do you know about grey water?

Let's find out what "greywater” is and how we can use it!

Continue!

Rainwater harvesting

Can do we collect rainwater? And how do we use it? Let's find out!

Continue!

Greywater recycling in practice

How a grewywater system is installed? Let's find out!

Continue!

Wastewater treatment

In this activity we learn about how wastewater is treated and what we can do with the treated water.

Continue!

The water cycle in a bowl!

Let's travel within the water cycle!

Continue!

Waterworks through time

Let's discover the story behind the historic fountains, cisterns and aqueducts of our town!

Continue!

Climate change challenges

Time to discuss about climate change, causes and impact and how we can cope with it.

Continue!

Rainwater Harvesting Systems in practice

What are the various types of rainwater harvesting systems? Let's find out more about them!

Continue!

Reduce-Reuse-Recycle

What is my water footprint and how can I reduce it?

Continue!

Water resources

Discovering the water resources of our region.

Continue!

Where do I begin?

Let's see why it is important to know about water in our region.

Continue!