Opinion (Spotlight Weekly)

Kosi Navigation Canal And Hooghly River

By Dr. AB Thapa

The Kosi Study Agreement 1997 has shown beyond doubt that the commencement of the construction of the Kosi High Dam would be contingent upon the prior implementation of the Sun-Kosi High Dam Project on technical grounds Similarly the study to construct the Kosi High Dam is now firmly tied up with the provision of a 165 km long navigation canal out of it a 120 km long section of such navigation canal would be in Indian territory. The proposed navigation canal would be linking Nepal with the seaport through Ganges, Bhagirathi and Hoogly rivers Thus India has not only endorsed our proposal to build the Kosi navigation canal linking Nepal with the seaport through Ganges, but it has even gone one step further. Government of India has agreed to bear the entire cost of the feasibility studies of the Sun-Kosi Dam Project as well as the Kosi Navigation Canal Project

It need not be explained that the feasibility of the Kosi canal navigation would be dependant on suitability of the Ganges and the Hooghly for navigation. As a result, the study of the Ganges, Hooghly and Calcutta port would have to be a part of the feasibility study of the Kosi navigation canal. It has been clearly stated in the .1997 Kosi study agreement that the economic study of the India’s Waterway No 1 linking Allahabad with the Haldia port would also form the part of the detailed study of the Kosi canal waterway.

The Hooghly River

The river Hooghly on which the port of Calcutta is situated takes off from the south bank of the Ganges River a short distance below Farakka. The head reach of this river is known as the Bhagirathi. The Hooghly River is formed by the confluence of the two rivers about 130 kilometres upstream of the Port of Calcutta. These two rivers are the Bhagirathi and the Jalangi. It is reported that they were once very active navigable waterways forming perennial navigation links between the port of Calcutta and its vast hinterland of Assam and Upper India but have now turned into spill channels receiving upland water for only about 3 to 4 months in a year.

There are few important tributaries which also join the Bhagirathi/Hooghly. The first of them, the Dwarka, rises in the Birbhum hills and joins Bhagirathi in Murshidabad district. The river has a length of 134 km and has a drainage area of 8,850 sq.km.

The Ajoy rises in the Santhal Pragana Hills and joins the Bhagirathi near Katwa. It's length is 276 km and it drains 6,050 sq.km.

The biggest tributary is the Damodar which is 541 km long and has a catchment area of 25,820 sq.km. It joins the Hooghly near Fulta point.

The tributaries Rupnarayan and Haldi joining the Hooghly have a catchment area of 8,530 sq.km and 10,210 sq.km. respectively. The total drainage area of all the tributaries joining the Bhagirathi-Hooghly is 60,000 sq.km.

Bhagirathi Dries Up

The major part of Bengal has been formed by mud and sand washed down by the Ganges, Brahmaputra and their tributaries. The south of the Gangetic Delta is still a land of swamps, creeks and forests. In the flat land, the rivers meander, swelling in the monsoon, shrinking in the dry season, often changing their courses and debouching into the Bay of Bengal through several channels.

In the past, the Bhagirathi was the main stream of the Ganges River. The Ganges runoff found its way into the sea by flushing out the silt and sand keeping the waterway through Calcutta region in good condition. It is said that less than three hundred years ago the Ganges showed a tendency to flow more and more through its eastern channel, the Padma. Ultimately the Bhagirathi turned into a relegated spill channel receiving water from the Ganges only for 3 to 4 months during the flood season.

The Calcutta and It's Port

A port on Hoogly is believed to have existed from the time immemorial. The Periplus, Ptolemy and Huen Tsang refer to ports on the Hooghly. The history of the present town of Calcutta, however, dates from 1690, when it was founded by the English East India Company.

Calcutta is located on the eastern bank of the Hooghly River. In past the Calcutta was transformed into the India's largest city due to the following reasons:

Calcutta became the capital of British India from 1772 for a very long time. Only in 1912 the capital of British India was removed from Calcutta to Delhi.

As the British power extended over the subcontinent, the whole north India became a hinterland for the port of Calcutta. The coming of railways and the inland waterways in the nineteenth century helped to transform Calcutta into India's biggest industrial and commercial centre.

Even now Calcutta is the world's largest processor of jute. Engineering constitutes the city's other major industry. In addition, city factories produce and distribute a variety of consumer goods - notably foodstuffs, beverages, tobacco, and textiles - other light manufacturers, and chemicals.

Even as late as 1950s the Calcutta port used to handle about 50% of the India's total exports. At present this port has lost its position as India's prominent cargo handler. However, this port still handles in terms of volume one-tenth of India's import cargoes and about one-twelfth of its export cargoes.

Impediments to Calcutta's Growth

The 20th century marked the beginning of Calcutta's distress. In 1912 the capital of British India was removed from Calcutta to Delhi. The partition of Bengal in 1947 was also a big blow. Calcutta became the capital of only West Bengal, losing the trade of a big part of its former hinterland. There is yet another big obstacle that impedes the development of Calcutta as the biggest industrial and commercial centre of India. It is the deteriorating condition of the Calcutta port and the virtual closure of the inland waterways that connected Calcutta with the hinterland in the east as well as west.

Calcutta is an inland port so its operation is highly sensitive to change in the river flows. The river regime is greatly affected by the changes in the river flows as a result of the tides and ebbs coming from the seaside and the upland water provided by the Bhagirathi river.

The progressive reduction in the upland flows entering the Bhagirathi particularly during the fair weather is said to be the primary cause for the deterioration in the port reach of Calcutta. The continued decrease in depths over the bars has been mainly due to the landward movement of sediment during the dry season. It resulted deposition of sediment in the estuary and the upper reaches of the Hooghly river. Such deposition continued to increase because they could not be flushed out due to inadequate supply of water entering into the Bhagirathi river.

The Hooghly river became shallower every year. Before 1948, ships with drafts of 7.8 m could come up to Calcutta almost throughout the year. In 1960s the permissible drafts for ships entering or leaving the part had considerably declined. The mean permissible drafts vary from 6.3 to 6.9 m, while the minimum draft in the dry months dropped to only 5.4 m. Shipping greatly suffered because the decreasing of each foot of draft results in a loss of about 600 tonnes of cargo carrying capacity.

Apart from the adverse effect on shipping, the gradual choking of the Bhagirathi channel made the water more saline. The water at the Fulta, where the pumping station for supplying water to the city of Calcutta is located, is undrinkable and unfit for industrial use. The proportion of salinity in unfiltered water in parts per million had increased from 400 in 1936 to over 6 times even in 1960s.

Resolving the Aggravating Physical Conditions

Apart from the decrease in depth of the head reach due to reduction of the upland flows the following other physical conditions are considered to be causing the deterioration of the Bhagirathi-Hooghly waterway.

Landward movement of the sediment during the dry season in the estuary and the upper reach as they could not be flushed out.

The occurrence of strong tides combined with shallow depth gives rise to "bore tide". With the reduction of upland discharge the flood current of the tides push the bed materials of the river upstream.

Cyclonic surges are also adverse physical phenomena for unhindered operation of waterways. Such surges do not occur regularly like the tides but they cannot be overlooked.

The Govt. of India seemed to have thought a long time ago to build a barrage across the Ganges River to divert the flow into Bhagirathi for resolving the worsening situation of the Bhagirathi-Hooghly waterway. Sir Arthor Cotton, an eminent engineer said to have proposed more than a century ago that if additional water were thrown into the Hoogly river, such an additional water might just make the difference of preventing the Hooghly from silting up.

The Farakka Barrage

The construction of the Farakka barrage was started in 1960s. The barrage began to operate from 1975. The over all length of the Farakka barrage on Ganges is 2240 m. It has 109 bays each of 18 m clear span. The barrage is designed to pass 73,000 cumecs of Ganges water. The pond level of the barrage is 22 m. The crest level of the spillway is at 15.6 m and that of the under-sluices and river sluices at 14.3 m. The head regulator is designed for 1130 cumecs. It has a clear waterway of 11 bays of 12 m each. Its full supply level at head regulator is 21.5 m and the crest level 18 m.

The feeder canal can divert up to 1130 cumecs of the Ganges water into the Bhagirathi. The length of the feeder canal is 37.5 km The bed width of the feeder canal is 150 m. Its depth at full supply level is 6 m.

A barrage has been built on the Bhagirathi at Jangipur to prevent the water fed into the feeder canal at Farakka flowing back into the Ganges. The Jangipur barrage is 210 m long and has 15 bays. The span of each bay is 12 m and the crest level is at 12.8 m.

The Navigation Locks

The Farakka lock helps to negotiate the difference between pond level of the Farakka reservoir and the water level of the feeder canal. The lock has two chambers, each 25.15 metres wide and 180.7 metres long. The lock is adequate for craft or barge train of up to 1,500 tonnes capacity. Provision has been made for adding a second lock at future stage.

A navigation lock has also been built to provide a navigation link from the Bhagirathi-Hooghly waterway into the Ganges-Padma and Banglashesh

(Dr. Thapa writes on water resources)