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Pakistan
Drainage
The continuous expansion of the irrigation system over the past
century significantly altered the hydrological balance of the
Indus River basin. Seepage from the system and percolation from
irrigated fields caused the water table to rise, reaching crisis
conditions for a substantial area. Around 1900 the water table
was usually more than sixteen meters below the surface of the
Indus Plain. A 1981 survey found the water table to be within
about three meters of the surface in more than one-half the cropped
area in Sindh and more than one-third the area in Punjab. In some
locations, the water table is much closer to the surface. Cropping
is seriously affected over a wide area by poor drainage--waterlogging--and
by accumulated salts in the soil.
Although some drainage was installed before World War II, little
attention was paid to the growing waterlogging and salinity problems.
In 1959 a salinity control and reclamation project was started
in a limited area, based on public tube wells, to draw down the
water table and leach out accumulated salts near the surface,
using groundwater for irrigation. By the early 1980s, some thirty
such projects had been started that when completed would irrigate
nearly 6.3 million hectares. By 1993 the government had installed
around 15,000 tube wells. Private farmers, however, had installed
over 200,000 mostly small tube wells, mainly for irrigation purposes
but also to lower the water table. Private wells probably pumped
more than five times as much water as public wells.
Officials were aware of the need for additional spending to prevent
further deterioration of the existing situation. Emphasis in the
1980s and early 1990s was on rehabilitation and maintenance of
existing canals and watercourses, on farm improvements on the
farms themselves (including some land leveling to conserve water),
and on drainage and salinity in priority areas. Emphasis was also
placed on short-term projects, largely to improve the operation
of the irrigation system in order to raise yields. Part of the
funding would come from steady increases in water use fees; the
intention is gradually to raise water charges to cover operation
and maintenance costs. Considerable time and money are needed
to realize the full potential of the irrigation system and bring
it up to modern standards.
Data as of April 1994
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