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Special
Reports/Water Crisis |
Efficient use of water in agriculture
By Abid
Hussain & Dr M. Ashfaq
BASICALLY, our irrigation system sustains the agriculture
sector. But the existing water resources are not used
efficiently, and are wasted at different levels.
 Loss
during storage, conveyance, application and irrigation are
causes of 65 per cent wastage out of the total 105 MAF
available at canal heads.
Irrigation has a larger impact on reducing poverty than rural
literacy. Increase in the adoption of high yielding varieties
(HYV)) and the use of fertilizers too, help in reducing
poverty but their influence is lower than the impact of
irrigation and rural literacy.
When irrigation water is enough, the cultivation of high
yielding varieties and fertilizers is also high. An astute
irrigation is the first prerequisite of high productivity.
Our farmers are bereft of optimum quantity of water for
irrigation due to two major problems; lack of storage
reservoirs and a major part of available water is lost during
conveyance from canal heads to fields.
Storage efficiency may be increased by improved management
while the lack of capacity of reservoirs to regulate
variations in incoming flows results in low storage. Thus, the
storage efficiency of dams would be increased when the
capacity is increased.
Conveyance, water use in irrigation and on farm application
efficiencies should be looked into. Huge quantity is lost
during conveyance from canal heads to fields via minors and
water channels.
Conveyance efficiency is defined as the net amount of water
delivered to a farm as a ratio of the amount taken from some
source. The difference between the two amounts represents the
seepage, management and evaporative losses incurred en route
from source to field. Conveyance efficiency is the possible
loss of water quality through pollution such as that caused by
wading animals or by human use of the canal water for washing
and waste disposal. Water quality is really affected in
Pakistan by pollution.
Conveyance losses may be subdivided according to the cause
into seepage; evaporation; leaks in structures in poor
condition; and poor water management in the distribution
network.
Irrigation efficiency may be defined in various ways depending
on the nature of inputs and outputs. An economic criterion
might be the financial return. Costs and prices fluctuate
every year and vary from place to place. Some costs and
benefits cannot easily be quantified, especially where a
market economy is not yet fully developed. Only short-term
costs and immediate benefits are seen.
How to assess the economic value of saving the population of a
region from the potential effects of a drought, if the
probability or severity of future drought events is not known?
To some degree, it is necessary to operate in a state of
uncertainty. In Pakistan water use efficiency is very low
because we lack conservation practices and enhancement of crop
growth.
The term on-farm or field application efficiency refers to the
fraction of water volume applied to a farm or a field that is
“consumed” by a crop, relative to the amount applied. Crop
consumption is the amount of water absorbed by the crop. Here
on farm efficiency is low as farmers use conventional methods,
fields are not levelled and soil texture fayed by the
intensive use of chemicals.
Due to above reasons the overall efficiency is 35.5 per cent.
Irrigation efficiency is a compound of three i.e., canal-head,
watercourse and on farm efficiency.
Problems like water shortage, theft, seepage and leakage,
silting, erosion of canal lines, conflicts, cutting of trees
from canal banks and many other pilfering activities have not
been stopped. If delayed further it may ruin our agriculture.
The idea of Nehri Punchayat System has been introduced in some
areas of Punjab, according to which farmers will participate
in irrigation management and decision-making. Let’s see which
way the wind blows. Can farmers’ community stop water losses
in conveyance and irrigation? Farmers have expectations from
this system but the government fears that the farmers will
unnecessary intervene in policy matters. That was why the
government was dallying full implementation of this system.
Implementation of the system will increase the productivity to
an optimum level. Water requirement for high yielding
varieties is more than for native. Fertilizer application
further increases the use of water because metabolic
activities in plants and microbial activities in soil increase
significantly.
If water shortage fear is eliminated from the mind of a
farmer, he will cultivate varieties of high productivity
targets. Farmers must be given a chance to resolve the water
problem.
For maximum efficiency, the idea of HELPFUL Irrigation is
ideal. It produces more than 90 per cent efficiency but is
difficult to manage. It is like a dream as astute irrigation
management enhances production. During the study it was
observed that moving from head to middle reach and middle to
tail reach decreases the production of crops because this
overall move from head to tail decreases the chances of
availability of water for cultivation.
In the canal head areas silting is lesser than that of middle
and tail reaches. Moreover, huge amount of water is lost or
spoiled by seepage, leakage, percolation, evaporation, theft,
animals, pollution and many pilfering activities while flowing
from head to middle and tail.
So, farmers at middle and tail reaches have to face more risks
of shortage and quality. Estimated production of farmers
living at tail reaches is more than the left areas because
they have no fear of shortage and loss.
Silting of canals and watercourses, paucity (water is not
available on time when available not in adequate quantity),
theft, unlined watercourses and canals, damages done by
animals to watercourses and canal lines, leakage, seepage,
high percolation rates and pollutants are major problems
farmers face as far as our irrigation system and its
management are concerned.
Farmers also claim that they are not provided with their
authorized quantity of water but pay full charges. Fields are
also unlevelled and conventional irrigation methods are
applied (surface irrigation/flood irrigation). Still, modern
methods should be applied to manage the limited volumes of
water.
Sprinkle, drip irrigations, subsurface exuders, sub-irrigation
are costly methods but once established there is no need to
spend every year on it. Small fruit orchards and vegetables
can be cultivated and irrigated by these methods.
In field, farmers should conserve water whatsoever its
quantity is. Conveyance losses should be decreased by lining
channels or, preferably, by using closed conduits. Runoff and
percolation losses must be avoided due to over-irrigation
because these losses are the right of others.
Evaporation from the bare soil should be reduced by mulching
and by keeping the inter-row strips dry. By doing this limited
available water can be conserved. In fields transpiration by
weeds should be decreased by keeping the inter-row strips dry
and applying weed control measures where needed. For efficient
use of irrigation water and high productivity all farmers
should adopt the following:
Select most suitable and marketable crops for the region
according to available water quantity.
Use optimal tillage (avoid excessive cultivation).
Apply manures and green manures where possible and fertilize
effectively (preferably when the irrigation water is
available).
Practise soil conservation for long-term sustainability.
Avoid progressive salination by monitoring water-table
elevation and early signs of salt accumulation, and by
appropriate drainage.
Irrigate at high frequency and in the exact amounts needed to
prevent water deficits, taking account of weather conditions
and crop growth stage. Over-irrigation must be avoided to save
water for other fields where it is required in huge volume.
Courtesy :
The DAWN
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Pakissan.com;
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