Opinion (Spotlight Weekly)

Kosi Canal Waterway: Vast Potential

By A.B. THAPA

Nepal and India signed an agreement on January 9, 1997 to jointly conduct a detailed study of the Kosi and Sun-Kosi (a tributary of the Kosi) storage dam projects. They agreed to conduct a detailed feasibility study on developing a navigable waterway extending from Chatra in Nepal to Kursella, the place where the Kosi meets the Ganges.Under the agreement, the waterway study would cover two alternatives: a navigation canal to link Chatra with the Ganges, and the use of the natural course. Unfortunately, the topography in India traversed by the Kosi is quite steep. There is an elevation drop of about 40 m between the Indo-Nepal border and the Ganges River on a north-south stretch of just about 120 km. Such high gradient results in increased flow velocity and small channel depths. Thus, the task of developing the Kosi river channel suitable for navigation by large vessels would be very difficult.

These difficulties could easily be overcome if we choose to have a navigation canal instead of relying on the natural course of the river. It implies that the Kosi canal waterway is in reality the only suitable option. Nonetheless, the study to canalize the natural course of the Kosi has been included keeping in mind flood control rather than navigation. The proposed study to canalize the natural course is necessary for training the Kosi in order to protect the surrounding areas from floods.

India's National Waterway No. 1

The Kosi navigation canal will be linked with the National Waterway No.1 of India, the stretch of the waterway between Allahabad and Haldia. The total length of this waterway is 1,580 km. The National Waterway No.1 of India includes the Bhagirathi, Hoogly and the lower and middle reaches of the Ganges. This waterway can be broadly divided into three sections. They are the Haldia-Farakka, Farakka-Patna, and Patna-Allahabad sections, the length of each being 500 km, 480 km, and 600 km respectively.

The meeting point of the Kosi waterway with the Ganges expected to be not far away upstream from the Farakka barrage would be within the upper reach of the Farakka reservoir. So sufficiently big water depths would be ensured in this reach of the Ganges.

Layout of the Kosi Navigation Canal

The Kosi Navigation Canal vis-a-vis India's National Waterway No.1 would provide Nepal access to the sea. This waterway should be planned on a par with the capacities adopted for the lower reach of the Ganges. The proposed Kosi navigation canal can be divided into two reaches. They are the 45-km upper reach between the Chatra and Birpur (near Indo-Nepal border) and the 120-km lower reach between the Birpur and the Ganges. The Upper Reach Canal will be entirely in Nepalese territory.

The Kosi High Dam Project Report prepared by the Indian government proposes to build a canal from Chatra to the Birpur area to deliver silt-free water from the Kosi storage reservoir for irrigation in India to the east of the Kosi. This canal would be 130 m wide. There is a drop of about 40 metres between Chatra and Birpur. It is proposed to build three powerhouses along the canal to utilize the topographical gradient for the generation of electricity. The capacity of each such power station is expected to be about 100 MW.

The canal proposed to be built for delivering water from Chatra to the Birpur for irrigation and power generation could also be used for navigation purposes. The proposed irrigation canal is sufficiently wide for use as a navigation canal. However, the canal would require significant modifications. A navigation canal requires adequate water depths at all places and at all times. Similarly, it would also be necessary to take into account matters related to free board, and the protection of the bank and the bottom of the proposed canal. The canal would need navigation locks for negotiating the fall across the powerhouses. There would be three locks parallel to the powerhouse in the upper reach canal between Chatra and Birpur. The exact size of these navigation locks should be adopted after careful study.

The Lower Reach Kosi canal would be completely in Indian territory. The north-south slope of the lands in this reach of the Kosi canal would be less steep compared to the slope of the lands in the upper reach. Nonetheless, there is a drop of about 40 m in a north-south distance of 120 km. It might be necessary to provide three to four locks to negotiate this drop. These drops could also be used for power generation. Similarly, the navigation channel running to the Ganges could be used for delivering water for irrigation. For this purpose, the outlets from this canal will have to be provided without cross regulators.

There are several dead channels of the Kosi running almost parallel to the proposed navigation canal. These dead channels meet the present Kosi river channel just before the point where the Kosi empties into the Ganges. It would be worth examining the possibility of developing one of these dead channels to be used as a navigation canal if it does not involve serious environmental problem. Such canalization of the dead channel would be requiring provision at several places dikes, check structures, navigation locks to improve the hydraulic regime and to overcome impediments to navigation.

Size of Navigation Canal and Locks

The dimension of various structures of the Kosi navigation canal should be adopted based on the size of the Farakka locks and navigation channel. It would certainly be desirable to adopt the same size. Such dimension of the navigation structures would be adequate for the operation of barges of 1,500-ton capacity. The proposed irrigation cum power canal between Chatra and Birpur is 130 meters wide. The width of the proposed Kosi canal exceeds the size required for its use as a navigation canal. The width of the lower reach Kosi canal could, however, be considerably reduced if it is to serve exclusively for navigation. We might adopt the width of this canal somewhere in the range between 70 m and 100 m. It is the minimum width for I and II classes (topmost) navigation channels in the former USSR. The minimum water depth in the Farakka canal is 4 meters. The same navigation depth could be adopted for the Kosi navigation canal. Farakka lock has two chambers each 25.15 meters wide and 187.7 meters long. This dimension could also be adopted for the Kosi navigation locks. The minimum depth of water at the sill might be taken to be 3.5 meters. Such lock size would permit passage of barges up to 1,500 tons or more in capacity. It would also be necessary to adopt the filling time of the lock chambers that would determine the ultimate capacity of the waterway.

Bank and Bottom Protection

The banks and bottom of navigation canals are affected by ship induced hydraulic load. The external loads produce both shear stresses and upward pressures on the protection layer. The dimensions of the bank protection material are determined by these external loads. The regulation of navigation behavior is also very important for canal navigation. By providing appropriate speed limitations, ship distance to canal bank, etc. the erosion of the unprotected canals or the lifting of canal linings can be prevented. All these hydraulic phenomena should be fully considered in planning the Kosi navigation canal.

Inland Navigation Ports

The Kosi canal waterway will require development of an inland navigation port in Nepal. Sunsari could be the appropriate location. This port to be located at a suitable place not far away from the East-West Highway could develop as one of the biggest commercial cum industrial centers of Nepal. The site of this port should be very carefully selected. There could be unbelievable expansion in commercial and industrial activities in and around the port area.

(The writer is water resource expert)