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FAO And Sunkosi Dam Project By AB Thapa The necessity of the
irrigation development on a large scale
in Nepal had been keenly felt since
the middle of 1960s. Bearing in mind such
necessity of large scale irrigation
development, the experts of the Food and
Agriculture Organization ( FAO) and the Government
of Nepal had carried out the First
Phase study of the Sun-Kosi Terai Project in
1965 and 1966 to determine the possibility of
irrigation development in the Eastern Terai
Plain by diverting the abundant water of
the Sun-Kosi River. The Interim Report on
Feasibility Study of the Sun-Kosi Terai
Project was submitted in October, 1969. The
plan to divert the Sun-Kosi River into
the Kamla River has been described in
that report. The final feasibility report
was submitted in October, 1972. The feasibility report
makes it perfectly clear that the people in
Nepal are mostly dependant for their food
supply and livelihood on a narrow belt of
cultivated land in Terai. The potential new
land for cultivation is very limited in
Nepal. Thus, there is a need to raise
agricultural productivity by intensification; i.e. by
increasing the average cropping intensity. The
Sun-Kosi diversion could help to provide
sufficient water round the year to increase the
cropping intensity as well as the per
hectare yield, as a result, the agricultural
production could be substantially increased. Sun-Kosi Kamla
Diversion Two possible diversion
plans had been identified for further study
at the end of the First Phase study.
They were called "A" Plan and "B"
Plan. Under Plan "A", the Sun-Kosi River
was to be diverted into the Trijuga River,
a tributary of the Sapta Kosi River,
through a tunnel about 7 kilometers long
to irrigate lands on the right bank of
the Sapta Kosi. Similarly under the Plan
"B". the Sun-Kosi River was to be diverted
into the Kamla River through a headrace tunnel
about 15 kilometers long to irrigate both
sides of the downstream reaches of the Kamla. The field survey
activities were started in October 1967. The
whole dry season of the year 1967/68
was spent in identifying the most feasible
plan. Following the surveys and studies
of both the alternative plans, it was
found that the "B" Plan to divert the
Sun-Kosi River into the Kamla was the
most feasible irrigation project. The selection
of the Plan "B" for further study was
approved by the FAO Headquarter and also
by the Government of Nepal. The dry
season of the following year 1968/69 was
devoted to conduct semi-detailed surveys and
the studies of the Sun-Kosi Kamla Diversion
Project. Meantime, the general studies of
irrigation development was also undertaken that
covered a vast region of cultivated lands
in Terai approximately 500,000 ha in area
from Kosi on the east to the Nepal-India
border line ( about 20 km to the west from Birjung )
on the west. According to one of the
studies the diversion of the regulated
flow of the Sun-Kosi River could provide
more than sufficient water needed for
year round irrigation of lands within
the project area estimated at 300,000 ha
in net coverage. Agricultural Studies Extensive agricultural studies
of the whole project area were made in
course of the feasibility study. General
reconnaissance soil survey of the Eastern Terai
plain is one of them. The survey report
gives the results of the reconnaissance soil
survey covering the entire project area of
540,000 hectares in gross. It was revealed
that about 80 percent of the entire area
has good soils for irrigation farming belonging
to Grade I, II and III according to the USDA
standard. No alkalinity or salinity problems exist. A special pilot farm
was set up at Hardinath in Dhanukha
district to conduct agronomic studies. Such
studies covered cultivation of crops like paddy,
wheat, sugar cane, maize, mustard, fodders and other
vegetables. Tests were conducted to determine
the irrigation water requirement, optimum sowing
time, optimum use of fertilizer, selection of
best varieties etc. Project Area The Terai Plain consists
of the alluvial fans and the recent river
deposit which are gently sloped from north
to south. The elevations at the foot of
the Churia Hills range from 150 to
slightly over 200 meters. The plain has gentle slopes
ranging from 1/1,000 at the foothills to
1/5,000 at the border line with India. The
countless small streams and rivers have
their origin in Churia Hills. They feed the
plain until they reach the Ganges or its
main tributaries. The Project area lies
between the Kosi River and the Indo-Nepal
border line at a distance of about 20 km to
the west of the Birgung town. Similarly the
Churia Foothill is the northern boundary
while the Indo-Nepal border the southern.
The project area is nearly rectangular in
shape. The length is about 240 kilometers and
the width varies between 20 and 40 kilometers.
The total project area is about 8,500 sq. km. out
of it in 1970s when the feasibility study
was made the gross cultivated land, reclaimable land,
non-reclaimable land (mainly river beds) and forests on
flat land were 5,450 sq. km, 570 sq. km, 650 sq. km
and 1,870 sq. km respectively. The project area covers
8 districts of Terai. They are Parsa, Bara,
Rautahat, Sarlahi, Mahottari, Dhanukha, Sirha and Saptari. The
total population in the project area in early
1970s was about 1,770,000 whereas, according to
the Statistical Book published in 1994 by
the Central Bureau of Statistics it had
increased to about 3,600,000. The River The Sun-Kosi River is
the biggest tributary of the Kosi River.
The total drainage area of this river at
Tribeni (near Barahachetra ) is 17,960
sq. km. At this point all three
main tributaries join and further downstream
the river is called the Kosi. Hydrometric
records covering the period between the years
1948 and 1967 showed that the yearly
mean discharge of the Sun-Kosi River at Tribeni
varied between 932 cu. m/sec. and 622 cu.
m/sec. The estimated yearly mean discharge
of the Sun-Kosi River ( based upon the
data at Tribeni ) at the proposed
dam site varies between 871 cu. m/sec. and 576
cu. m/sec. The annual average
sediment load of the Sun-Kosi River at
Tribeni according to some studies is
about 54 million cu. m The annual average
sediment load of the Kosi at Tribeni is
about 119 million cu. m. The Sun-Kosi Dam The FAO had
provided Nepal technical and financial
assistance to conduct the study of the
Sun-Kosi dam project for the agricultural
development in the Terai Plain that had
three main functions. They were capital
formation needed for social investment through
the increased income of farmers, sufficient
food supply for the whole country, and
increased employment in the Terai Plains.
The Government of India had also investigated
the Sun-Kosi dam site in 1940s. At that
time India was exploring the possibility of
building the Sun-Kosi dam primarily for
controlling the Kosi River floods. The Indian
survey team had favoured Kurule dam site
on the Sun-Kosi River because it appeared
geologically sound and allowed to have a
big storage reservoir that extended in
Dudh-Kosi and Sun-Kosi valleys. In all
subsequent studies that followed thereafter the
location for the dam at Kurule
has remained unchanged. The site for the
Sun-Kosi dam proposed in the FAO supported
study is also at Kurule. The Master Plan
study of the Kosi River water resources was
made in 1985 by JICA ( Japan Government
Agency) team. The Sun-Kosi River diversion for
irrigating lands in the Eastern Terai had
been identified as one of the top
priority projects in the Master Plan study.
That study too had adopted the Kurule
as the appropriate location for the dam
across the Sun-Kosi River to divert it
into the Kamla River. Water Right Issue The FAO provided
assistance to Nepal in revising the 1954
Kosi River Treaty. Dr. Dante A. Caponera, Chief,
Legislation Branch of FAO, Rome was in Nepal in
1966. The Kosi Treaty was revised on 19th December, 1966.
Nepal's full right over the Kosi River water has been
very clearly explained in the revised
treaty. The Article 4 ( i ) of the Treaty
related with the water rights has been
presented hereinafter: "HMG shall have every right to
withdraw for irrigation and for any other purpose in Nepal
water from the Kosi river and from the Sun-Kosi river or
within the Kosi basin from any other tributaries of the Kosi river as
may be required from time to time. The Union (
it indicates India ) shall have the right to
regulate all the balance of supplies in the Kosi river at
the barrage site thus available from time to time and
to generate power in the Eastern Canal." Geology A separate report on
the Geology of "B" Plan Area as
a part of the Sun-Kosi Project feasibility
study was prepared by Dr. J. B. Auden in
January 1967. Dr. Auden is well known for his great
contribution in the field of Himalayan geology.
An abstract of the geological investigations
has been presented in the report
"Feasibility Study of Irrigation Development in
the Terai Plain, 1972". Power Development
Planning In planning the Sun-Kosi
diversion, three options were considered. They
are the diversion plan exclusively for
irrigation, non-peaking power development option, and
peaking power development option. At present the available
minimum discharge of the Sun-Kosi River at the
diversion site is about 140 cum. m/sec. It is
proposed to build a 34 m high dam
and a 15,000 m long diversion tunnel 6 m
in diameter to divert 140 cu m/sec. Sun-Kosi
River water if this project is to be
planned exclusively to irrigate lands in
Terai. The next alternative is
the Sun-Kosi diversion project along with
a non-peaking hydropower station. The diversion
project would be having a 73 m high dam
and a 15,000 m long tunnel 8.4 m in
diameter to divert 215 cum. m/sec flow.
Installed capacity of the hydropower station
would be 330 MW. The third alternative is
the Sun-Kosi diversion along with a peaking
hydropower station. The diversion project would have
a 115 m high dam and a 12,700 m long
tunnel 8 m in diameter There would
be another dam at Kakaru. The firm discharge
140 cu. m/sec diverted from the Sun-Kosi River would
be stored in a pondage to be provided
on the Kakaru Khola, at about 8 kilometers
upstream from Amtai Bazar. The required storage
capacity at that pondage was determined to be
about 9.6 million cu. m to meet the peak
load with load factor of 21 percent, which
would correspond to daily peaking time of
5 hours. The installed capacity of the
hydropower station would be 1,050 MW. JICA Study Japan International Cooperation
Agency (JICA) had helped Nepal to carry out
the Master Plan Study of the Kosi River
water resources development. The final study
report was submitted on March, 1985. Three
reservoir type schemes have been planned for
the Sun-Kosi River. They are the Sun-Kosi No. 1
Dam, Sun-Kosi No. 2 Dam and the Sun-Kosi No. 3 Dam
schemes. The lowermost is the Sun- Kosi No. 1
Dam Scheme. The Sun-Kosi No. 1 Dam according
to JICA study and the Sun-Kosi dam
proposed in the FAO supported irrigation
development study are virtually one and the
same. The sole difference between them is
over the dam height. The FAO study has
proposed a dam about 120 meters in
height, whereas the JICA study recommends dam
height in between 147 and 195 meters. (Thapa writes on water resources) |
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