الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Efficient drainage systems must ultimately be provided on all
irrigation projects when natural drainage conditions are inadequate
to remove surplus water and salts Timely performance of
preventative and regular maintenance on project drainage systems is
absolutely necessary if the systems are to perform the functions
for which they w·ere designed and built . Project drainage systems
should be thoroughly examined periodically to determine if they are
functioning and if maintenance is required .
The well functioning drainage sys~ems in irrigated arid and
semi-arid regions are essential to maintain soil productivity at a
certain level . The collector drains are designed in a composite
subsurface drainage system to collect the outflow of lateral drains
and evaoua~e them to the open drain in tbe area . They are also
designed to work without overpressure ; not restricting the lateral
outflow and the t:ow of ground water from the soil to the drainage
system . Conse~~ently , the main function of collector pipe is to
transport the lateral discharges to the open drain .