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Pancheshwor Project Irrigation In India — I By AB Thapa The Mahakali River forms
the boundary between Nepal and India. A
dam is proposed to be built across
the Mahakali River at Pancheshwor. The dam
is expected to be over 300 meters in
height. According to the pre-feasibility study
of this project the volume of the storage
reservoir would be 11.3 billion cu. m.
The average annual flow of the Mahakali
River at the dam site is 654 cu. m /sec.
After the completion of the Pancheshwor Project
the flow of the Mahakali River would
be fully regulated. It would be possible
to provide constantly throughout the year an
average flow estimated at 654 cu. m /sec if
the water losses on seepage and evaporation
are not taken into account. At present
during the critical months in dry season the
80% probability discharge of the Mahakali River
at the dam site comes down to about 90
cu. m /sec. Thus, it is very important to
implement the Pancheshwor Storage Dam Project
to increase the dry season flows. Diversion Structures in
India India has already built
in their territory diversion structures across
the Mahakali, Karnali, Babai, West Rapti and
even Banganga rivers to irrigate lands. All
these diversion structures are linked by
a long canal that extends from the Lower
Sarada barrage built across the Mahakali River
to the Banganga River barrage . The diversion
barrage built across the Karnali River at
Girjapur in India is at the center. The
Saryu canal with a capacity to
irrigate 1,200,000 ha takes off from the left
bank of the Girjapur barrage and connects
all the rivers to the east of the
Karnali River. Similarly, another 28 km long
canal (known as the link canal) taking off from
the right bank of the Girjapur barrage
delivers the Karnali River water into the
pond of the Lower Sarada barrage built
across the Mahakali River in India The
Sarada Sahayak canal provided to
serve a vast area of 2,000,000 ha
takes off from the right bank of the
Lower Sarada barrage. The layout of the
existing canal system allows the
regulated flows of the Karnali or the West
Seti rivers to be delivered into the pond
of the Lower Sarada barrage built across
the Mahakali River. However, in
a similar manner after the completion of the
Pancheshwor Project the regulated flow of
the Mahakali River reaching the Lower Sarda
barrage can not be conveyed to the upstream
pond of the Girjapur barrage built across
the Karnali River. Thus the regulated flow
of the Mahakali River can not be used to
irrigate lands within the command area of
the Saryu canal system. It implies that
in the post Pancheshwor Project period
a good proportion of the dry season
flow of the Karnali River that reaches
the Girjapur barrage might have to
be diverted to irrigate lands within the
command area of the Saryu canal. It
is a very important consideration that
should be borne in mind in developing
Nepalís water resources plans. Sarada Sahayak Canal The Sarada Sahayak canal
draws water from the Lower Sarada barrage built
across the Mahakali River in Indian territory.
Soon after the completion of the Pancheshwor
Project the Lower Sarada barrage would be
expected to draw in a very big
scale the Mahakali River water discharged
into the river after power generation.. The length of the
Sarada Sahayak canal is about 260 km
out of it about 146 km long stretches are
lined. It has five branch canals. They
are the Daryabad Branch, Bara Banki
Branch, Haidergarh Branch, Rae-Bareli Branch and Purwa
Branch. The total length of the branch,
secondary and tertiary canals is 8704 km. The
command area of this project extends over
a vast area to the west and
south of the Karnali River (
known as the Ghaghra River in
India). The command area of this project
borders on the towns like Balia,
Varanasi, Allahabad, Lucknow etc. Cropping Pattern Information on present
cropping pattern adopted in the command area
of the Sarada Sahayak Canal Project was
provided by Indian authorities to
the consultants conducting the feasibility study
of the Karnali Multipurpose Project under the
aegis of the World Bank. At present the
agriculture development is limited by the availability
of dry season water. The Pancheshwor Project
would help to increase significantly the
dry season flows and allow higher irrigation
intensities in the areas served by
Sarada Shahayak Canal. At present the crops
grown in the Sarada Sahayak Canal Project
area are early paddy, medium paddy, maize, fodder (kharif),
sugarcane, early wheat, late wheat, potatoes and oilseeds.
The cropping intensity for the present
situation is 96%. Now the cultivation of
crops is very much dependant on
limited dry season flow of the Karnali
River drawn from the Girjapur barrage. The
28 km long link canal that delivers water
from the Girjapur barrage built across the
Karnali River to the Lower Sarada barrage
has a capacity of only 480 cum/sec,
despite the fact that the Sarada Sahayak
Canal drawing water from the Lower Sarada
barrage has a much higher capacity of 650
cum/sec. Thus, it was proposed in the
feasibility study report of the Karnali Project
to enlarge the capacity of the link
canal. The situation would be altogether
different if the Pancheshwor Project is to
be implemented first In the post
Pancheshwor Project period, it would not be
necessary to divert to a greater
extent the Karnali water to irrigate lands
within the command area of the Sarada
Sahayak Project. After the completion of
the Pancheshwor Project the regulated flow of
the Mahakali River would be quite sufficient
to meet the additional irrigation water demand
and therefore it would not be necessary
to enlarge the size of the link canal. Water Balance The water balance
study of the Sarada Sahayak Canal Project
has been extensively made in the
feasibility study of the Karnali Dam (Chisapani)
Project. The major findings of that study
could be directly applied to the
Pancheshwor Project. It is explained in the
Karnali Project feasibility study report that 35% of
the diverted flow is assumed to evaporate
or be transpired, and 65% must return via surface and
groundwater. Of the 65% returning, 15% is assumed
to be lost to deep subsurface flow, leaving 50%
for return as surface water and shallow
groundwater. The water balance study
was made for the present situation to
determine the existing level of water
utilization and also to provide a basis
against which future scenarios could be
compared. Water balance for the future scenario
was calculated to ensure that the required
75% irrigation reliability is met. Additional Irrigation
Infrastructure The Sarada Irrigation
Project drawing water from
the Sarada Sahayak canal covers an area
of about 2,000,000 ha. At present the cropping
intensity in the project area is
only 96% but it was expected to increase
from the present 96% to 129.5% within
a very short period soon after the
completion of the Karnali Multipurpose Project
because with the exception of 28 km long
link canal, that needed some readjustment, all
other irrigation structures were already in
operation. It has already been explained
that the capacity of the Sarada Sahayak
canal is 650 cum/sec, whereas the capacity of
the link canal to convey Karnali water
into the Lower Sarada barrage that diverts
water into the Sarada Shayak canal is only 480
cum/sec, as a result, it was necessary to
enlarge the capacity of the link canal.
The cost of such enlargement of the link
canal was included in the estimates of
the Karnali Project feasibility study report.
It is evident that such enlargement of the
link canal would not be necessary if
the Sarada Sahayak canal is to get
additional supplies from the Pancheshwor
Project. Thus, in case of the Pancheshwor
Project the build up period to
increase the crop yield to projected
level could be even shorter. Criteria For Economic
Evaluation It is tried to
present a rough estimate of the incremental
agricultural benefits accruing from the
regulation of the Mahakali River flows by
the Pancheshwor storage reservoir directly based
on the feasibility study of the Karnali (Chisapani)
Dam Project After the significant
enhancement of the dry season flows of
the Mahakali River it would be possible
to adopt improved cropping patterns, as a
result, the agricultural benefits would be
greatly increased. It is assumed based
on the feasibility study of the Karnali
Project that the build up of irrigation
intensity will continue over a period of
three years. Economic prices for inputs
and outputs would be at 1988 price
level. The irrigation benefits have
been determined discounting to November 1, 2003, at
10%. The average annual flow
of the Mahakali River at Pancheshwor is
654 cum/sec. It is presumed that the total
net irrigation benefits accruing in both the
countries would be equally divided between
the two countries. The net irrigation
benefits to be accrued from irrigation in
Nepal would be only nominal because of
the high cost of new irrigation
infrastructures that are yet to be built.
Thus the net production value for
Pancheshwor Project irrigation in Nepal would
be small despite the fact that the gross
margin might be very high. So, Nepal
would have hardly anything to share with
India. For the rough estimation of the
Pancheshwor Project benefits to be
accrued from irrigation in India
it is randomly presumed that an average 400
cum/sec Mahakali River regulated flow would be
provided to India. Total Irrigation
Benefits It has been stated
in the Karnali (Chisapani) Project feasibility study
report that it would be possible to
obtain net irrigation benefits discounted
at 10% up to US $ 9 million for each
cubic meter regulated flow supplied to the
Sarda Sahayak Canal if such water is
fully utilized. Thus the total discounted net
irrigation benefits could be as high as US $
3,600 million if the 400 cum/sec average
flow is supplied from the Pancheshwor storage
reservoir. Feasibility study of the Kankai
Multi-Purpose Project had been made by the
German consultants. The Kankai Project irrigation
benefits are almost on a par with
the Pancheshwor Project irrigation benefits. Kankai Multi-Purpose
Project Benefits Detailed feasibility study
of the Kankai Multi-Purpose Project was carried
out in 1978 by the German Agency
for Technical Cooperation (GTZ). The project included
a very large irrigation component. The average
flow of the Kankai River is about 40
cum/sec. The present worth of the total
irrigation benefits discounted at 10% in
1978 was US $ 164 million. Thus, the
benefit discounted at 10% in 1978
was about US $ 4 million for each cubic meter
per second regulated flow used in
irrigation. However, the present worth of costs
to be incurred in irrigation infrastructure
development was also very high. So, the
present worth of the net irrigation benefits
discounted at 10% was ultimately found to
be only US $ 58.5 million in 1978. Expected Irrigation
Benefits It might be at this
stage too optimistic to expect that the
regulated flow of the Mahakali river
would be totally used in irrigation.
The Karnali Project consultants have very
conservatively made an assessment of the
irrigation benefits with the expectation that
the water supplied to irrigate lands would
not be fully utilized. The data
provided in the Karnali Project feasibility
study report in reference to the enlargement of
the Karnali link canal explain that
if the canal capacity is raised by
170 cum/sec the cropping intensity over an
area of 2,000,000 ha would be increased
from 111% to 130%, as a result,
there could be an increase of about
US $ 700 million in total discounted benefits
at 1988 price level. Thus it could
be possible to expect that the total
discounted net irrigation benefits could
be roughly US $1,600 million
if 400cum/sec water is supplied to Sarada
Sahayak Canal Project. However, it should
also be noted that such total net benefits
would be on lower side because in
calculation of the gross margin for present
and future situations the present crop
yields might be on higher side, whereas
the future yields on the lower side. For
example the present yield of wheat is as
high as 2.4 tons/ha against the future
yield of just 2.8 tons/ha, as a result, the
increase in crop yield with the project
is quite small. Similarly the increase in
yields of the crops like the sugarcane,
maize adopted in the evaluation is on
lower side. (Thapa writes on water resources) |
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