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of southeastern regions of Tunisia and is the foundation of agricultural activities in
this zone. The system retains water in dams made from earth or stone, perpendicular
to the runoff, behind which crops, mainly fruit trees, are cultivated. The dam stops
and stores the runoff to supply the crops. Jessour is generally used in mountainous
areas where they are often built into wadis, but they are also constructed on plains.
The dams encourage infiltration of rainwater which not only intensifies agricultural
production but recharges the groundwater. During extreme rainfall, part of the disas-
trous runoff can be retained behind the dams to reduce the potential damage caused
by floods (Majdoub et al. 2014 ).
4.4 Groundwater Harvesting
Groundwater harvesting (GWH) encompasses all methods, traditional or contempo-
rary, of harvesting water from the ground for productive use. It has also been used
as a storage method for the other forms of water harvesting outlined above, with
many of these techniques requiring a particular terrain to divert the water from its
original source so it can seep into the ground for crop use. Traditional methods of
GWH have used underground dams, sand dams, wells, cisterns and aquifers
(Rockström 2002 ).
Extraction of subsurface water flow, either from soil water trapped in shallow
sand layers or from the water table, constitutes an interesting form of water harvest-
ing. Storing water underground is attractive as it reduces evaporation losses and
often contributes to high-quality water thanks to filtration, e.g., through sand (even
though soil and geological characteristics will determine the level of filtration
capacity). Sand dams and subsurface dams, where water is trapped behind small
dam walls in sandy riverbeds, is an efficient and cheap form of water harvesting
(SIWI 2001 ).
Wells are probably the most common GWH technique; they tap into the water
table from a hole excavated on the surface (Figs. 13 , 14 ). Wells have been employed
as a source of water for thousands of years, dating back to 8100–7500 BC. Like
other forms of water harvesting, wells have been adapted to meet the needs of indi-
viduals living in specific regions. Technology has also increased the returns from
wells, making it easier to obtain water (Prinz 2002 ).
Cisterns are manmade caves or underground constructions to store water. Often
the walls of these cisterns are plastered to prevent water loss, deep percolation and/
or evaporation (Prinz and Singh 2000 ). The underground cistern supplies water for
domestic and irrigation purposes in drought-prone areas. There are two variants to
this cistern, one being shaped like a bottle, the other in a circular form. Both are
constructed in a similar fashion with the ground excavated to form the shape of the
cistern. The surface is covered with polyethylene or concrete plastering to avoid
seepage. Both cisterns are expensive and difficult to build, and often too complex
for farmers to construct themselves (Alem 2003 ).
A. Yazar and A. Ali