Opinion (Spotlight Weekly)

Challenges Of Harnessing Himalayan Water Resources

By A.B. THAPA

Finding new ways of exploiting the vast water resources in the Himalayan region poses a major challenge to scientists and technicians in the 21st century. The diversion of the Brahmaputra through Nepal into the Ganga could be one such engineering problem. Hydro-electricity development has enormous potential for the Himalayan region. Glacier-fed rivers are notorious for their very high sediment load. Glacier lakes are also important elements in the catastrophic variation of downstream river regime. All these problems would require extensive study. Leading international institutions like the Global Infrastructure Fund (GIF) taking keen interest in Himalayan water resources study or the International Center for Integrated Mountain Development (ICIMOD) could be appropriate institutions for this type of study. About two decades ago, the Royal Nepal Academy of Science and Technology (RONAST) had carried out an exercise to set up a regional center on snow and ice in Nepal. At the time, it was thought that the proposed center would facilitate such a study.

Growing Demand For Water

The supply of water is gradually dwindling in the Ganga basin of South Asia because of the ever-growing demand for water. It was one of the main causes of the souring of relations between India and Bangladesh in the past. The recent Farakka agreement between India and Bangladesh on Ganga water sharing has helped, to a great extent, to resolve this problem. However, both countries accept the fact that sooner or later the present dry season flow of the Ganga must be augmented. There are two scenarios being discussed. India proposes to divert the Brahmaputra at Jogighopa in Assam through Bangladesh into the Ganga near Farakka. Bangladesh proposes to build storage reservoirs in the Ganga basin itself to augment the dry season flow. Each country is sticking to its own proposal and a compromise appears remote. There could be other alternatives also. One possible option is briefly explained in the Water and Energy Commission Secretariat (WECS) study on the Kosi river. It relates to Brahmaputra's diversion through Nepal into the Ganga.

In the book "Eastern Water Study", scientists at Harvard University have stressed the need of creative thinking about assessing inter-basin transfer of water options, including trans-Himalayan prospects using the Gandak or Kosi for diversion from Tsangpo (Brahmaputra). Such diversion could be very effective in mitigating the problem of growing shortages of dry season flow of the Ganga and also in the generation of cheap electricity.

Brahmaputra River

The source of the mighty Brahmaputra river, known as Tsangpo in China, lies in the Cheme-Yungdong Glacier near Lake Manasarobar in Tibet. This river flows for 2,900 km from its source to its confluence with the Ganga in Bangladesh. This river enters Bangladesh as the Jamuna. The mingled water of the Ganga and the Jamuna (Brahmaputra) empties into the Bay of Bengal. Not until early in the last century was it certain that the Tsangpo and the Brahmaputra were the same.

WECS Concept

The diversion of the Brahmaputra into the Arun river from a suitable place not too far away from Sigatse (in China) could be one option. The Brahmaputra is a very big river and its valley must be deep compared to Arun's. This implies that a long tunnel would be required to create such a diversion. The tunnel length could be considerably reduced by adopting the following two measures. (1) Building a high dam across the Brahmaputra to elevate the water level and for storage. (2) Building a pumping station if further elevation of water level is desirable. This could be single or multi-stage pumping for delivery of water into the Arun system. Due to vast differences in the climatic conditions of the tropical Indian subcontinent and alpine-type environment of the Tibetan plateau, the adverse effects of Brahmaputra's diversion on Tibet might not be too significant. The diversion is required mainly in spring and winter. In the rainy season of the summer, the diversion is not necessary because there is always plentiful water in the Ganga.

In the Brahmaputra region of Tibet, like in all similar regions of the north, spring is the time of plentiful water. The Brahmaputra must be in high floods in spring when snow lying below the perpetual snow line completely melts. Such abundant floodwater could be diverted into the Ganga. On the other hand, spring is a period of acute shortage of water in the Ganga.

The diametrically opposite spring-season hydrological characteristics of the upper reach Brahmaputra and the Ganga make trans-Himalayan diversion an attractive option. The prospect of diversion of the Brahmaputra into the Ganga in autumn and winter also is worthy of study.

Tibet needs water for irrigation mostly in the summer when the ambient temperature is sufficiently high to support agricultural crops. After a very short warm period of summer, the temperature starts to drop. Towards the middle of autumn, before the temperature plunges close to freezing point, harvesting and sowing for the next season's crops should be completed. This signifies that during autumn, the use of Brahmaputra water in Tibet would be only limited. Thus a good proportion of the autumn flow could also be diverted without adverse effect on Tibet's agriculture.

In winter, everything on the surface, including the top layer of river water, remains frozen in Tibet. Beneath the ice, however, the water of the Brahmaputra would be flowing even in the coldest day of the year. There could hardly be any chance of utilization of such water in Tibet in appreciable quantity. A good proportion of Brahmaputra's winter flow could be diverted to augment the Ganga.

The diversion of the Brahmaputra into the Ganga would allow the generation of cheap electricity on a large scale. There is a drop of about five kilometers in elevation between the Tibetan plateau and the Ganga plains. This big drop could be used for power generation.

Study Of Snow And Ice

Snow and ice, representing both valuable resources and natural hazards, are significant elements of the world's hydrological systems, which occur subject to tremendous variations in space and time. Nowhere is the change more significant than in the advancing and retreating tides of snow and ice. RONAST was hoping that the proposed regional center would be engaged in scientific studies of the snow and ice balance of individual catchments and of regional groupings of catchments forming the headwaters of major rivers.

The proposed regional center was also to promote sustainable economic and social development. As such, it would have consisted largely of applications-oriented studies with both scientifically and socially valid objectives.

Hydropower development has enormous potential for the Himalayan region. Effective site analyses, as well as decisions on scale of capital installation, depend on determination of annual water supply and its seasonal variation. In addition, glacier-fed rivers are notorious for their very high sediment load. This, of course, relates to the rate of reservoir sedimentation and rate of capitation damage to turbines. Response to these problems can be made through dam, reservoir, and penstock intake design, which in turn will be influenced by detailed glacio-hydrological studies.

In the Himalayan region, glaciers disrupt communication systems and various infrastructures like hydropower plants directly or indirectly by impondment of an ephemeral lake which subjects the mainstream to periodic catastrophic floods. Such floods also produce peaks in sediment transfer.

Regional Cooperation

RONAST established relations with the Italian National Research Center (CNR) to carry out joint Himalayan studies. A big research center equipped with modern facilities has been set up near the Mount Everest base camp at Lobouche. The CNR provided invaluable assistance to Nepal in reconfirming that the Everest is the highest mountain in the world. On March 7, 1987, the New York Times declared that, according to measurement taken by an astronomer of the University of Washington, the highest mountain in the world was K-2. The CNR disproved that claim and re-established Everest's position.

The proposed regional center on snow and ice would have been the most appropriate institution to help the Brahmaputra diversion and similar studies. The actual study could be undertaken by GIF or ICIMOD or any similarly capable organization.