Brooks-Tayaa: Sidebar 3. Traditional water detention and diversion practices
in Morocco
Water diversions are traditional methods of using flash flood
water to irrigate local crops in the drier parts of Morocco. These systems
are well adapted to the local conditions and are used to irrigate areas
close to or within the watercourse. In Morocco, more than 165,000 hectares
are irrigated using these traditional water diversion practices. Three types
of these water diversions are described below:
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Lateral diversion:
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Earth dike diversion:
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This is an improved version of the lateral diversion.
The primary objective is to provide head for an off-take in order
to irrigate greater areas. Its use is restricted to streams with relatively
low slope gradients, pronounced banks and medium width. The dikes
are constructed of primitive material such as gravel and sand excavation
from the river bed.
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Small retention dams:
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This practice is usually encountered in the Saharan
zones where floods are less frequent and with limited runoff volumes.
It consists of small earth or loose rock dikes (up to 1.5m height)
constructed across the river and designed to store flood water for
crop cultivation (mainly barley) in the river bed upstream of the
dam and to recharge groundwater. It is practiced in wider rivers having
lower slope gradients and appropriate bed material for cultivation.
They are occasionally washed out and this insures, particularly for
the diversion dams, a self cleaning of the sediment deposited upstream
of the dikes. The reconstruction and maintenance require a tremendous
effort in terms of labor supported totally by farmers, which is a
way of keeping solidarity within the community.
Modern technology has been introduced into flood diversions, but is largely
inspired from the traditional practices. With reinforcement, these structures
provide better control of the diverted floods and protect the structure
itself.
(Tayaa 2001)
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