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Access to sufficient clean drinking water is vital, as people cannot go long without it. However, this is not always possible in areas with low rainfall, low surface water or unpredictable rainfall. Residents should then have a strategy for long-term water availability and recycle gray water.



  1. Watch the film ‘Blue Gold World Water Wars'. And discuss with students their experiences with (drinking) water.
  2. Design and build a scale model for a rainwater harvesting system that does not use electricity for pumping water.*
  3. Design a helophyte filter for one household.**

* Rainwater is usually collected on roofs or landscaped slopes and then stored in cisterns or tanks next to houses. Excellent manuals for this are available from The International Rainwater Harvesting Alliance. Usually, the first rainwater is drained away after a dry period. The rest of the rainwater is then stored and used for distribution or in an alternative piping system in the home. A sand filter is often used between the storage tank and the house. This can be flushed periodically.

** Helophyte filters are constructed with surface flow (SFCW) or under flow (SSFCW). The first uses plants that grow in the ground above an impervious layer. The SFCW operates in a flooded state. An SSFCW uses about 700 mm of gravel applied above an impermeable layer and the wastewater flows horizontally about 100 mm below the surface of the gravel – hence “underflow. Plants are grown in the gravel with their roots in the water below the gravel surface. Typical plants used in constructed wetlands are Phragmites Australis, Typhus and Scirpus.


Learn to design integrated systems for rainwater harvesting, filtering and reuse.

Learning outcomes:

Understand basic principles of the water situation at a given location. Learning to develop a rainwater harvesting and greywater filtering system.


Flipchart, gravel, plastic edging (as a water barrier), shovels, metal or plastic pipes 10 cm thick, other piping.


All students can see and critique the collection and filtering models. What didn’t work as it should have? How can this be improved?

What did the students learn about the technical and practical aspects of rainwater harvesting and treatment with grey water? How does this fit into society? How can this be used in the rest of the world? What was the most important thing that happened in this activity? What issues are they still missing?


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