At the receiving end

All of these enter the Bay of Bengal, carrying large volumes of water and silt. An extensive network of khal and beel (canals and wetlands) helps channel floodwater for agriculture and fisheries. The two systems are, therefore, central to Bangladesh's flood plain ecology. Simultaneously, a constant flow ensures silt removal, while the level at which rivers flow bear on navigation activities and groundwater recharge.

The vast flooding experienced by Bangladesh during the monsoon is not caused by local rainfall; it takes place as a result of water carried by rivers into the country. A total of 57 rivers enter Bangladesh, which is landlocked on three sides. Out of these, 54 rivers originate in India. Thus any intervention in the Himalayan river system in India is bound to affect Bangladesh. What needs to be ascertained is the extent of disturbance that the process is likely to create.
Impact simulation Questions were first raised about India's river networking scheme during the Third World Water Forum at Kyoto in March 2003, where both Nepal and Bangladesh expressed reservations. Interestingly, at the same meet, the river basin-sharing issue was also discussed widely. It was argued that unilateral intervention in river basins shared by more than one country should be avoided, as it leads to trans-boundary conflicts. A possible list of such zones was mentioned and the Ganga-Brahmaputra-Meghna basin figured in it.

Fearing an adverse fallout from the project, in September 2003 the Bangladesh government asked the Dhaka-based Institute of Water Modelling (iwm), a consultancy group, to find out the extent of likely damage. iwm used a default model of the Bangladesh river system as it runs currently. "We had to change the variables according to the river-linking project's proposed quantum of water withdrawal, since that amount won't be available to us," reveals Emaduddin Ahmad, the executive director of iwm. "But it was important for us to be aware about the amount of water transfer that would take place in each basin; merely knowing the total was not enough," he adds.

Another crucial bit of information the model-makers didn't have was the timing of the transfer, as water required for various activities is always season-specific. Not surprisingly, unavailability of this data seems to have raised the hackles of experts in Bangladesh. But unlike anti-river linking activists in India, iwm conducted extensive research using the basic data available in the public domain. It also studied India's agricultural pattern to understand the timing of water withdrawal, and so came up with a model that ran on various options.

Bangladesh has an annual average water endowment of 1200 billion cubic metres (bcm). Almost 93 per cent of this is through the 57 rivers entering from outside. According to published data, India is supposed to transfer about 224 bcm of water annually from Himalayan rivers, which is 25 per cent of the annual water endowment from the Ganga and Brahmaputra rivers.

There has been a major public outcry in Bangladesh over the siphoning of Ganga water by India through the Farakka barrage. With southwest Bangladesh reeling under increased salinity because of the low flow of the Ganga, the likely impact of the river-linking project on the flow of the Brahmaputra is fresh cause for concern.

Jahir Uddin Chowdhury, a professor in the Institute of Water and Flood Management of the Bangladesh University of Engineering and Technology (buet), is categorical about the expected damage due to any water transfer from the Brahmaputra (see table: Gauging the depth): "The effect of the Farakka barrage will be negligible compared to that of tinkering with surplus water in the Indian Brahmaputra." Crucially, the river gives Bangladesh about 60 per cent of its water endowment.