Inter-basin water transfer

It is possible that the water availability in a basin (Watershed) is not sufficient to meet the maximum demands within the basin. This would require Inter-basin water transfer, which is described below:

The National water policy adopted by the Government of India emphasizes the need for inter-basin transfer of water in view of several water surplus and deficit areas within the country. As early as 1980, the Minister of Water Resources had prepared a National perspective plan for Water resources development. The National Perspective comprises two main components:

a) Himalayan Rivers Development, and

b) Peninsular Rivers Development

Himalayan rivers development

Himalayan rivers development envisages construction of storage reservoirs on the principal tributaries of the Ganga and the Brahamaputra in India, Nepal and Bhutan, along with interlinking canal systems to transfer surplus flows of the eastern tributaries of the Ganga to the west, apart from linking of the main Brahmaputra and its tributaries with the Ganga and Ganga with Mahanadi.

Peninsular rivers development

This component is divided into four major parts:

1. Interlinking of Mahanadi-Godavari-Krishna-Cauvery rivers and building storages at potential sites in these basins.

2. Interlinking of west flowing rivers, north of Mumbai and south of Tapi.

3. Interlinking of Ken-Chambal rivers.

4. Diversion of other west flowing rivers.

The possible quantity of water that may be transferred by donor basin may be equal to the average water availability of basin minus maximum possible water requirement within basin (considering future scenarios).

Note: A Donor basin is the basin, which is supplying the water to the downstream basin.

The minimum expected quantity of water for recipient basin may be equal to the minimum possible water requirement within basin (considering future scenarios) minus average water availability of basin.

Note: A Recipient basin is the basin, which is receiving the water from the Donor basin.

National Water Development Agency (NWDA) of the Government of India has been entrusted with the task of formalizing the inter-linking proposal in India. So far, the agency has identified some thirty possible links within India for inter-basin transfer based on extensive study of water availability and demand data.

Note:

The National Water Development Agency (NWDA) was set up in July, 1982 as an Autonomous Society under the Societies Registration Act, 1960, to carry out the water balance and other studies on a scientific and realistic basis for optimum utilization of Water Resources of the Peninsular rivers system for preparation of feasibility reports and thus to give concrete shape to Peninsular Rivers Development Component of National Perspective. In 1990, NWDA was also entrusted with the task of Himalayan Rivers Development Component of National Perspective.

Possible components of an inter-basin transfer project include the following:

•         Storage Dam in Donor basin to store flood runoff

•         Conveyance structure, like canal, to transfer water from donor to recipient basin

•         Possible pumping equipments to raise water across watershed-divide

Possible implications of inter-basin transfer: Since a large scale water transfer would be required, it is necessary to check whether there shall be any of the following:

•         River bed level rise or fall due to possible silt deposition or removal.

•         Ground water rise or fall due to possible excess or deficit water seepage.

•         Ecological imbalance due to possible disturbance of flora and fauna habitat.

•         Desertification due to prevention of natural flooding (i.e. by diversion of flood water)

•         Transfer of dissolved salts, suspended sediments, nutrients, trace elements etc. from one basin to another.