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Cisterns

The principal idea of cisterns or storage tanks is the collection of rainwater for storage and use as drinking water for domestic needs, animal watering or irrigation. A cistern is a man-made hole in the soil with a gypsum or cement coating to avoid vertical and lateral infiltration losses. Generally these underground reservoirs with capacities from 1 m3 to 70000 m3 occupy the outlet of a small catchment area (impluvium) that collects the rainwater. In a natural Environment the impluvium is demarcated by one or more grooves or small stone bunds conveying the runoff water towards the opening of the storage tank. The water passes a decantation basin that retains plants, silt and other material that is carried by the runoff water. One or two openings in the covered top, which constitutes the protection against evaporation, allow the taking of water.



Figure 18: Cross section of majel and fesguia (Chahbani, 1997)

In Tunisia two different kinds of cisterns or storage tanks can be found: the “majel� and the “fesguia�. They are distinguished according to their form (see figure 18). Generally fesguia have a larger storage capacity, but their construc­tion is accordingly more expensive.

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