dawn 21 may 2007
Pakistan may become one of the worst hit country because of the
global warming and there are signs of it turning into a desert due
to water scarcity. India will get two times the monsoon rains and
Afghanistan is likely to become a green land. Now is the time to
foresee the impending calamity and to plan management the water
resources by avoiding massive water wastage in our obsolete canal
irrigation system.
As there is huge surface water wastage — up to 60 per cent-- in our
highly wasteful supply-based canal system and from other sources,
there is a dire need to identify these areas and to check water
wastage.
The total estimated figure of surface water wastage is about 82 maf
out of 142 maf.
These waste flows are from the wasteful irrigation system, the
floodwater waste flow to sea and the loss of water in the wide
waterway of the Indus River bed.
This massive wastage needs be controlled control by the combined
processes of Integrated Comprehensive Water Management (ICWM). The
net water available to crops at the farm after the wastage of 82 maf
is about (142-82=) 60 maf. This is a colossal economic loss is a
problem of mismanagement and not water scarcity. Besides, there
would yet be another incoming enormous wastage of surface water
between 35-40 per cent of the 142 maf as a consequence of the global
warming and glacier melting. Assuming only 35 per cent shortage, it
comes to 142x35 per cent0=50 maf. This huge shortage of water would
be in the second permanent phase of the global warming after about
30 years. Besides,the water losses in the 14-miles wide and
meandering Indus River between Chashma to Kotri is about 14 maf. The
riverbank return flow or gain in winter in the Indus is about 6–7
maf. The net loss of water in the Indus River comes to about (14-7)=
7 maf. This loss of water can be controlled by channelling the Indus
River.
Alternately, to avoid most of the water loss in the Indus River
waterway, the water shares of Sindh and Balochistan can be diverted
from Chashma barrage on the Indus via Sibi in Kachi plain to enter
Sindh province. This diversion is possible by lined canal with
gravity flow through the proposed All Pakistan Grand Canal supported
by Katzarah Dam. The only way to counteract water shortage in the
Indus Basin is to carry out integrated comprehensive water
management (ICWM)as follows:
Storage dams: The construction of long life storage dam is vital
part of water management to conserve, regulate river flow, control
and store super-floods and generate cheap hydropower for the use of
sprinkler and drip irrigation methods. Storage dams control silt and
act as watershed management infrastructure. Silt free water is a
great advantage for the use of drip and sprinkler irrigation methods
that can irrigate about three times more area than with flood
irrigation. The support from storage dam is a must for the demand-
based canal irrigation system as it releases regulated water
supplies as and when required in proper doses.
It can provide water to crops on the crop consumptive use basis in
time in proper doses for maximum yield as the present Warabandi
system of the supply of water with fixed time duration on area basis
is obsolete. Demand-based irrigation system: This system is the
basic and vital component of water management to avoid most of the
water wastage from wasteful supply-based canal irrigation system.
Therefore, the obsolete, highly wasteful, 150 years old supply-based
canal irrigation system needs immediate replacement. The demand-
based system would result in colossal saving of about 50 maf in
surface water. It is most efficient water conveyance system to
supply water to crops in time for maximum yield.
The adoption of modern irrigation practices is must for agricultural
development using sprinklers and drip irrigation methods after laser
levelling of land, land reform and land consolidation. Plot of land
for irrigation should be given geometrical shapes. All these
processes are vital part of ICWM. Sprinklers and drip irrigation
methods of using water if practiced can irrigate about three times
the area than by flooding method.
Pipe supply: Traditional watercourses should be replaced by pipe
supply as far as possible. This saves seepage and evaporation losses
besides theft of water. Hydropower generation to run sprinkler and
drip system is the vital instrument in the processes of ICWM.
Drainage: The drainage system for irrigated agriculture is an
integral and very vital component of irrigation and water
management. This is missing in the Indus basin irrigation system
since 150 years to evacuate the injurious saline effluent out of the
area and control water logging. As a result, drainage effluent has
accumulated as groundwater. Moreover, natural drainage is also
blocked due to encroachments. No surface and sub-surface tile
drainage is provided to evacuate injurious salinity, control water
logging and maintain salt and water balance.
Drainage is the missing part of irrigation and is vital to keep
water table under control and keep irrigated land healthy. As a
consequence of no drainage system, about 60 per cent of irrigated
lands in the Indus basin suffer due to salinity, sodicity and water
logging to various degrees. Crop yield on this account is low and is
seriously affected.
The right type of drainage system is extremely vital to evacuate
injurious saline effluent out of the area, control water table,
reclaim land and keep salt and water balance for optimum crop yield
otherwise precious fresh surface water is wasted on diseased land.
SCARPs and NDP were wrongly conceived mega drainage projects thereby
both projects have not only failed but added more salinity and
sodicity in soil. As a consequence of drainage accumulation and its
misuse, Punjab is pumping about 45 maf of injurious saline
groundwater drainage effluent for irrigation use that destroys its
land invisibly without the farmers knowing it.
It is estimated that if this practice of using saline groundwater
drainage effluent continue, the Indus basin would turn as saline
waste by the year about 2030. Therefore drainage must be provided as
it is the vital part of ICWM and integral component of irrigation.
Warabandi system: Warabandi system of 1887 for the supply of water
has become obsolete as under the supply-based canal irrigation
system. It supplies water to crops on land area basis and fixed time
limit. This is to be replaced by crop consumptive use of water as
and when required in proper doses under the demand-based irrigation
system supported by long life storage dam. It will produce maximum
crop yield per acre.
The major sources of water wastage are the old obsolete supply-based
canal irrigation system where about 100-105 maf of surface water is
diverted in canal system out of 142 maf of the available surface
water. About 50 maf of water is wasted due to seepage from the
supply-based canal irrigation system. The next major source of water
wastage is 25–35 maf of floodwater waste that goes to sea during
monsoon. Besides this, about seven maf of water is lost in the bed
of the Indus River that needs channelling to save water. The total
water wastage on these three counts comes to about (50+25+7)=82 maf
out of 142 maf of water. What a great water wastage due to utter
mismanagement of precious water? .
In the first phase of global warming in about 30 years from now,
there would be increased river flows due to glacier melting often
resulting in super floods. In the second, and final phase of global
warming, there would be 35—40 per cent reduced surface water flows
on permanent basis. On this account the loss of surface water due to
global warming comes to about (assuming only 35 per cent loss)=
(142x35%)=50 maf of water. Besides this, hydropower generation from
storage dams would also be reduced by the same amount. Therefore
maximum number of dams should be built.
If ICWM is not implemented, the irrigation system in the Indus Basin
would almost have no water as (82+50)=132 maf of water would be lost
out of 142 maf The ICWM and its integral components can save about
72 maf of surface water from wastage. Therefore ICWM needs to be
planned right now for immediate implementation as it would require
at least 30 years for completion. If ICWM is delayed or avoided, the
Indus basin irrigated agriculture would be ruined.
The writer is a former chairman of IRSA
