Opinion (Spotlight Weekly)

Responsibility For Western Terai Submersion

By A.B. THAPA

Large hydraulic structures built on Indian territory very close to the Nepal-India border are at present causing widespread submersion inside Nepalese territory. This type of action, which results in appreciable harm to the other country, is against the principles of international law even if such structures would have been located at a considerable distance away from the border. The structures need not be within a distance of 5 or 10 kilometers from the border to constitute a breach of international law, although some of our own people at the policy-making level and the media are often seen expressing ideas that contradict such view.

The submersion of lands in the terai of western Nepal resulting from the structures built in India has emerged as a problem of the greatest importance to our country. Four districts of the western Terai are affected. A few years ago, the flooding was limited to Banke district along the banks of the West Rapti river. Subsequently, it extended further east to Kapilabastu and Rupandehi districts. We ourselves might be responsible to a great extent for the submersion of our lands that has caused widespread human suffering in Nepal. If the attention of our country is not immediately drawn to this problem, the flood situation is going to be far worse in the years ahead and we would also lose our ability to exercise control over the situation.

West Seti Storage Dam

Nepal has embarked on a plan to launch three major storage dam projects in western Nepal completely disregarding how the vast quantity of regulated water is going to be utilized in India. The feasibility study report of the Karnali Project carried out at an enormous cost provides in depth information on downstream uses, but we are not interested in looking into them. Our concern is only electricity. While the fate of the Karnali and Pancheshwor projects are yet to be decided, the West Seti project is virtually in the hands of a private developer. The decision to go ahead with the West Seti project should be immediately revoked until the matters related with the downstream uses remain unsettled because this project is directly linked with the submersion of lands in Western Terai near the border with India.

The Girjapur Barrage

The Girjapur barrage across the Karnali river is located 1.2 km downstream of the confluence of the channel Girwa and Kauriala and 8.8 km downstream of Katarnia Ghat railway station of North Eastern Railway in India. The site of the barrage is about 16 km from the Nepal border along the River Kaurila.

There are two irrigation canals taking off from the Girjapur barrage. On the left is the Saryu canal running to the east beyond the Banganga river and on the right is the Link Canal connected with the Sarda Sahayak canal planned to irrigate about 2 million hectares of lands. At present, only the right bank canal is operational because the dry season flow of the Karnali river is quite insufficient for both the canals and there are technical difficulties to utilize the monsoon flow of this river. The year-round operation of the Saryu canal depends entirely on availability of the regulated flow from the proposed storage reservoirs in Nepal. The construction of the Saryu canal, which started a long time ago, is still continuing at a snail's pace perhaps due to uncertainty about the date when the West Seti project would be ready for operation. Nevertheless, it appears that the Saryu canal could be made operational at short notice after the completion of the West Seti Storage Project because most of the structures of the Saryu canal might be already ready. After that our people near the border area would be forced to live virtually in swamps throughout the year.

Layout of the Saryu Canal

The Saryu canal project consists of a canal network that connects the head regulators of the barrages across the Saryu (Babai river), West Rapti and Rohini (Banganga river). A link channel 48.4 km long taking off from the left bank of the Girjapur barrage outfalls into the Saryu river just upstream of a barrage across it. A link canal 56 km long taking off from the left bank of the Saryu river outfalls into the West Rapti river just upstream of the Laxmanpur barrage. Beyond that a 125-km long canal taking off from the left bank of the West Rapti river extends up to the Banganga river.

How the Submersion is Caused

The total length of the Saryu canal running almost parallel to Indo-Nepal border is about 230 km. In the original design the barrage across the Saryu river was at a location about 328 meters to the south of the railway bridge at Nanpara. Later, the design was modified and the location of the barrage was shifted 10 km to the north from the original site. The longitudinal gradient of the Saryu canal has been reduced to a minimum. It is only one meter on a stretch of 9 km. The adoption of such extremely mild slope permitted the alignment of the canal to be pushed as far as possible to the north very close to Indo-Nepal border specially in its middle and lower reaches.

Normally siphons are provided to deliver canal water across a river. A much higher average slope of the canal is required for the operation of this type of cross drainage structure, which has to operate under pressurized condition. A free flow hydraulic regime needs to be maintained at the river crossing if the average gradient of the canal is to be reduced. For reducing the average slope of the Saryu canal an altogether a different type of structures has been devised, which at first glance drives anybody crazy. Barrages have been built across the rivers to elevate the river water to such a level that would allow free passage of canal water across the river into the canal taking off from the other side of the river The contentious Laxmanpur barrage is one of such structures devised to deliver the water from the Girjapur barrage across the West Rapti river.

It would be necessary to maintain all the time pond water upstream of the barrage above certain fixed level to keep the Saryu canal running at desired capacity. Thus the pond would always be full, with the result that a sizeable area of lands in Nepalese territory could remain perpetually submerged. When the river is in flood, the water would be spreading out onto the lands that were never before regarded prone to flooding.

The Saryu canal is expected to cross innumerable small rivers and drains on its way. Embankments and dikes are needed to train these drains and small rivers for the protection of the Saryu canal. These river training structures could also result in widespread flooding inside Nepal where the canal route is close to the border.

A through study should be carried out based on confirmed data to determine exactly the impact of the Saryu canal on Nepalese territory. It would also be necessary to determine how far to the south the Saryu canal must be shifted once it is established that the proximity of the canal alignment to the border is the cause of the present flooding in Nepal.

Nepal should not commit a blunder by continuing to go ahead with the decision to implement the West Seti project before resolving the present flood problem in Western Terai.

(Thapa is a water resources expert)