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| GENERAL DEFINITION OF THE TECHNIQUE |
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| Technique: |
HYDRAULIC DEVICES |
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Definition characters description and diffusion
When there are particular geographic conditions, specific water technologies form the basis of the entire landscape organisation.
General characters description and diffusion
This is the case of the high mountains in the Valais region in Switzerland. Here the winds sweep the slopes after having released all their humidity in the ascending phase along the opposite slopes, and in areas that should be humid at this latitude, they give rise to piedmont deserts, chasing away the clouds, creating high pressures and arid conditions. The fields would not look green and fertile if they were not irrigated by the bisse, which draw water from the glaciers or from the head-waters of streams and carry it through the mountain ridges and down the arid valleys, creating settlements, pastures and crop fields at the bottom. The same practice, called ru, is present in Valle d’Aosta. Under different geomorphologic conditions, the water system known as feixe is used on the island of Ibiza to control alternating situations of excess water and of aridity. Marsh water is drained into a network of channels and then conveyed along porous pipes beneath the fields. Thus the crops can tap the water they need directly through their roots, by means of the feixe system that regulates winter excesses and saves water during summer droughts. In the Negev desert, along the Wadi Araba and in Jordan the prehistoric remains of innumerable hydraulic devices prove the existence of appropriate techniques for making the desert fertile and life-supporting by capturing humidity and protecting the soil. Similar devices are found in the Saharan Neolithic, in the Arabian Desert and in the Yemen and they subsequently spread all over the Mediterranean. In some circumstances the water supply is only available in the underground sediments. Consequently, surface run-off takes place thanks to embankments that, using the water intakes located at the bottom, tap the water harvested on the deposits upstream of the dam. When this system does not work, water is extracted by means of wells that thanks to underground dams catch the humidity stored in the subsoil. The buckets are lifted up by a long rocker arm that is fixed with a balance weight and placed on two tall adobe uprights. This technique is known as khottara in the Algerian Sahara and is similar to the Arabian shaduf technique. In Yemen, during dry seasons the water preserved in the sediments is taken from wells built by means of a typical Yemenite technique that ensures maximum saving of the energy used by the dromedary to pull the rope with the bucket full of water. The well is raised several metres above ground level and the top can be reached by means of a long ramp. The dromedary follows this steep path without wasting any energy while the empty bucket goes down. Subsequently, when the dromedary lifts the full bucket by pulling the rope keeping itself far from the well it is favoured by the downward path of the ramp.
Advantages and sustainability
A variety of hydraulic devices are used depending on each climate and its specific characteristics and needs. These hydaulic devices capture or create water for populations and the proceses that make their survival possible.
Images
Deepening
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TRADITIONAL TECHNIQUE DATA
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| Reference: |
www.ipogea.org |
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