On the distribution of water of the Teesta river, a bilateral treaty between Bangladesh and India would have been signed in the presence of the Prime Ministers of both the countries at Dhaka on 6.9.11, but for the objection of the Chief Minister of the State of West Bengal in the interest of the State. Political matters should be set aside so far as the rivers of the Ganga-Brahmaputa delta are concerned. Under no circumstances, interrelation between the major rivers of the undivided Bengal can be ignored.
What the Bengal Irrigation Department had handed down to the posterity have been published by the West Bengal District Gazetteers, Higher Education Department, Government of West Bengal, under the name of ‘Rivers of Bengal’. There are 5 volumes, which contain maps of the rivers drawn over a period of 150 years under the British rule.
The Map of Major Rennell drawn on the basis of the survey made by him between 1764 and 1777 reveals the following
(a) Coming down to the plane from the hills, the old Teesta bifurcated about 20 miles below after flowing past Siliguri. The left branch was known as the Karatoa and the right one bifurcated into channels known as the Punarbhaba and the Attreyi rivers. The former joined the Mahananda river and the latter, after flowing along the oldest course of the Koshi river and then through the Chalan Bill, used to fall into the Hoorasagar(Baral) river, emanating from the Padma at Sharda. The beheaded old Teesta still exists under those three names.
(b) Rounding the Garo hills, the Brahmaputra used to fall into the Meghna flowing past Mymensingh.
(c) There was a silted up old spill channel known as the Konai-Jenai, connecting the Karatoa near Goalanda, from a point a little below the turning point of the Brahmaputra.
(d) After meeting with the Hoorasagar river, the Karatoa river used to flow past Dhaka under the name of the Buriganga river.
A very high flood occurred in the Teesta in 1787. The old course having been blocked up by numerous logs brought down from above by the flood water, the Teesta diverted its flow into its thoroughly silted up very old former course. The devastation that the Teesta had caused has been described in detail in Hunter’s ‘Statistical Account of Bengal’ and in the Rangpur District Gazetteer. The new and the old courses of the Teesta have been shown in the Sheet No. 2 of the Map No. 1, attached with the Volume II of the ‘Rivers of Bengal”. Other maps, which have been referred to, are required to be correlated with this most authentic Map No. 1 as far as possible.
The above-mentioned map shows a peculiar direction of flow of the Teesta in the last part of its course. Suddenly turning to the south, it flowed for about 12 miles before falling on the head of the Konai-Jenai. It can be ascertained from that map that the last part of the Teesta was on another silted up spill channel of the Brahmaputra, originating from above that turning point and connecting the Karatoa below the town of Bogura.
The huge discharge of the Teesta set into motion the resuscitation of the Konai-Jenai. Getting scope to enter its water into its discarded spill channel, the Brahmaputra gradually enlarged the Konai-Jenai. Abdandoning its previous course past Mymensingh by 1830, the Brahmaputra started flowing, taking to the course of its former spill channel under the name of Jamuna . Having been reinforced by the water of the Teesta, the Jamuna became larger than the Brahmaputra.
Two barrages have been constructed on the present course of the Teesta, one at Gajaldoda in the Jalpaiguri district and another at Lalmonirhat in Bangladesh. The former has been constructed with a view to irrigating 9.22 lakh hectares of land spread over 6 districts of North Bengal. Apart from the construction of the barrage, only a quarter of the Teesta Barrage Project has been completed so far, in consequence of which only 60 thousand hectares of land can be irrigated at present.
The Teesta water-distribution treaty could not be materialized owing to the reluctance of the State Govt to spare more than 25 thousand cusecs of water during the lean period to Bangladesh, whereas their demand was 33 thousand cusecs of water from the Gajaldoba barrage. As because water coming down in the rainy season can only be stored in that barrage, there should not be any difficulty in meeting the present demand of Bangladesh at the present stage of the Project. So the problem must be lying elsewhere, which has not yet come to light.
It is stated in the ‘Rivers of Bengal’ that the Teesta flood water carries heavy silt change. The impounding capacity of a barrage across such type of river keeps on declining due to the heavy siltation. Sudden release of excess water is causing flood in Bangladesh. To irrigate as much land as is contemplated will remain as building a castle in the air.
It is also stated in the ‘Rivers of Bengal’ that the deltaic rivers do not care for the political boundaries and those also do not forget their past courses. There was a high flood in the koshi river in 2008. Flood water having been blocked up by the Koshi-Barrage,the river outflanked breaching the embankment and made for the Chalan Bill in Bangladesh through North Bengal following its silted up old course. The devastation that the river brought about in the State of Bihar is worth remembering.
In the event of a high flood, the Teesta, finding the barrage as a huge impediment on its way, may switch over to its old course past Siliguri. In order to forestall the destructive power that the Teesta can manifest in North Bengal and Bangladesh in its bid to flow through the three streams, early resuscitation of the old course is necessary. A canal dug from the nearby Brahmaputra may solve the problem of the Dalia barrage. There will be no dearth of water till the end of the lean period due to the early rainfall in the Assam Valley.
Construction of the two barrages on the course of the Teesta has weakened the Jamuna. Simultaneously, supply from the Brahmputra into the Jamuna has been on the wane on account of insignificance of the Teesta at the confluence. Back rush of the Brahmaputra flood will gradually close the gap. What is not being passed into the Jamuna from the Brahmputra is intensifying the flood in the State of Assam. Ultimately, the Brahmaputra is to take recourse to its previous course past Mymensingh for debouching into the Megha, which was , undoubtedly, an ancient course of a spill channel of the Brahmputra from its left bank.
In that region the Karatoa was the main river from time immemorial. Having been connected with at least two spill channels of the Brahmaputra from its right bank and the Hoorasagar/Baral river, initially an off-shoot of the Kalindri from below Godagari, the Karatoa was a large river below the town of Bogura. It bifurcated after it met with the Hoorasagar/Baral river. The upper channel flowing past Dhaka and Suvarnagram (Sonargaon) used to fall into the sea somewhere to the east of the town of Noakhali and the Padma is now flowing from Goalanda to the Meghna appropriating its lower channel [ Map of Van Den Broucke (1660 A.D)]. In Broucke’s time the Bhubaneswar and the Arial Khan rivers were the means for the flow of the water of the Padma to the sea. In Major Rennell’s time it used to debouch into the Tentulia estuary. The damming action of the Jamuna compelled the Padma to divert much of its flow into the Gorai-Madhumati combination. It is virtually the Brahmaputra which flows under the name of Padma from Goalanda to the Meghna, its ultimate destination. The Padma will be nowhere on the scene, if the Kalindri, the main stream of the Ganges till the 16th Century A.D [ Map of Joan De Barros( 1552 A.D)], becomes active once again as a result of heavy siltation in the up-stream of the barrage at Farakka. The Ganges-water will then pass through either the Kumar river [Sialmari + Mathabhanga + Lower Kumar] or the Bhairab river, or through both the rivers.
Lest the Brahmaputra deserts the jamuna completely, it is necessary to open the spill channel leading to Mymensingh as well as the spill channel on which the last part of the Teesta now exists. That will help prevent complete desertion of the Brahmputra from the Jamuna. Simultaneous flow of the Brahmaputra through those three channels will not only strengthen the Karatoa but reduce the fury of flood in the State of Assam as well. Unfortunately, the Karatoa was deprived of the head water-supply in consequence of the flood in 1787. Perenniality of the Karatoa must be restored as early as possible in the interest of North Bengal and Bangladesh. Late Satish Chandra Majumder, a famous Chief Engineer of the Bengal Irrigation Department, had laid emphasis on the diversion of a portion of the Teesta flood into its old course for amelioration of the drainage system of the then North Bengal.
All the maps are uploaded in http://swapankumarsinhasblog.blogspot.com/2010/05/in-context-of-farakka-barrage.html
