Dam, structure built across a
stream, a river, or an estuary to retain water. Dams are built to provide water for human consumption, for irrigating arid and
semiarid lands, or for use in industrial processes. They are used to increase
the amount of water available for generating hydroelectric power, to reduce peak discharge of
floodwater created by large storms or heavy snowmelt, or to increase the depth
of water in a river in order to improve navigation and allow barges and ships
to travel more easily. Dams can also provide a lake for recreational activities
such as swimming, boating, and fishing. Many dams are built for more than one
purpose; for example, water in a single reservoir can be used for fishing, to generate hydroelectric
power, and to support an irrigation system. Water-control structures of this
type are often designated multipurpose dams.
Auxiliary works
that can help a dam function properly include spillways,
movable gates,
and valves that
control the release of surplus water downstream from the dam. Dams can also
include intake structures that deliver water to a power station or to canals, tunnels,
or pipelines designed
to convey the water stored by the dam to far-distant places. Other auxiliary
works are systems for evacuating or flushing out silt that accumulates in the reservoir, locks for
permitting the passage of ships through or around the dam site, and fish
ladders (graduated steps) and other devices to assist fish seeking to swim past
or around a dam.
A dam can be a central structure in
a multipurpose scheme designed to conserve water resources on a regional basis.
Multipurpose dams can hold special importance in developing countries, where a
single dam may bring significant benefits related to hydroelectric power
production, agricultural development, and industrial growth. However, dams have
become a focus of environmental concern because of their impact on migrating fish
and riparian ecosystems. In
addition, large reservoirs can inundate vast tracts of land that are home to
many people, and this has fostered opposition to dam projects by groups who
question whether the benefits of proposed projects are worth the costs.
All that area of
blue waterways is flowing into the Indus, and down through the country. These
rivers include large gatherings into the Chenab, Sutlej, Zaskar, Nubra, and
Shyok, all of which spill into the Indus. Yes it does include some parts of
northern India/Kashmir and eastern Afghanistan. But note how it also covers
almost all of the land in northern Pakistan. So in the end,
almost every drop of rain that falls on Pakistan, from the northern mountains,
to the deserts, to the heartland, to the Iranian border, all of it already
flows further on into Pakistan for use. In the end, there's only a few tiny
slivers of land in the country where water falling on the country is lost by
flow to other countries (such as places like near Chaman). What may be
confusing about the image you gave is the gray colors up in the north, nearer
the Basha [as well as in southwestern Pakistan]. But those colors aren't
showing that water there isn't coming into Pakistan, but only that that area
isn't irrigated land. Basically all the water in those gray areas, like the
Pakistani portions of the Hindu-Kush/Himalayas/Karakoam Mountains, flows down
into the Indus and through Pakistan. Plus even more additional water from neighboring
countries. So in other words Pakistan gets more water than what falls on it.
Other countries definitely aren't so lucky. And that water is already coming
down into the rest of the country. In terms of feeding the
country, irrigation could maybe be expanded a bit... but I believe the problem
isn't just the lack of water... but that a lot of the rest of the soil is
fairly poor for growing. The book Pakistan's Soil Resources (available online)
classifies more than 1/4 of the country's soil potential as
"Agriculturally unproductive or non-agricultural land" due to wind
erosion, salinity, extremely low, etc. (Some additional land might be made
arable by leeching down salt levels, but I believe it would take long periods
of time and great amounts of water. Soil Quality and Agricultural
Sustainability, by Rattan Lal, (Google Books preview)
looks to include some interesting description of the greater complexities and
some long-term potentials of many areas of the world, including Pakistan.) On
the other hand, it sounds like the more urgent concern maybe isn't eating but drinking? (Disappointingly,
I think you'll find that most other parts of the world probably aren't very
aware of your problem... I certainly wasn't). Unfortunately this problem trend
is showing up in many other places, such as well-publicized recent issues
in southwestern South Africa. In the end,
the primary problem for much of Pakistan's population likely
doesn't stem from the complete lack of water... but instead from the lack of
needed infrastructure, pollution issues, and mismanagement, as this article alludes
to. These are issues that the entire world does struggle with (such as the
troubles in Flint in the USA).
There are already some parts of the world there are literally growing concerns
of not enough water existing in entire regions to sustain it whatsoever (such as in the SW US/impacting
NW Mexico) But if the Indus is flowing steadily down to the ocean through
your country (please do indicate if it’s not, the problem may be more
serious then!!), it's not a matter of no water, it's the challenge of detouring
enough to areas to meet needs, and keeping it clean. Karachi does look a bit of
a challenge area on a map.
The good news is it's only 60 miles from the Indus. Quite a few places source
their water from such a distance - some places even do get it from hundreds of
miles away, even from the far side of mountain ranges as
you kind of suggested. But the unique challenge is likely how flat the land is
in the south nearer Karachi. Places like California and Rome can take advantage
of elevation to better feed the distant water via gravity. Karachi on the other
hand may require much more pumping to get the water from the Indus, and that
might well not be cheap/easy over even distances like 50 miles? (As noted, it
looks like most of the N Pakistani Mountains are south of the continental
divide, so almost all their water flows your way already. The few miles of
snowpack flowing into Tajikistan and such a) may well be needed by their people
and b) could be diverted into the Indus with some effort... but that won't
solve problems if the Indus is already steadily flowing. The Suleiman Range
might offer some options to divert a little more water west of the Indus using
tunnels like in the LA Aqueduct... but that would depend a great deal on the
specifics of the topography and precipitation levels in those mountains for
feasibility.) So, indeed, all that water from your mountains is indeed flowing
right through the heart of Pakistan, "right by your window" almost
(plus the gift of extra input from areas of far northern India). It's just
getting it from the Indus to where it's needed. And it just needs to be taken
care of carefully.
