GLOBAL WARMING AND HIMALAYAN GLACIERS
By Dr. AB Thapa
Swedish chemist Svante August Arrhenius, noted for his Nobel Prize-winning work in the field of electrochemistry had made the discovery that helped to understand about the greenhouse effect. In 1896 he had calculated that doubling the natural concentrations of carbon dioxide in the atmosphere would increase the global temperatures by 4 to 6 Celsius degrees. His finding is not too far from today’s estimates using more sophisticated methods. Arrhenius correctly predicted that when Earth’s temperature rises, water vapor evaporation from the oceans increases. The higher concentration of water vapor in the atmosphere would then contribute to the greenhouse effect and global warming. Unfortunately, the predictions about carbon dioxide and its role in global warming set forth by Arrhenius were virtually ignored for over half a century.
Global Warming
Towards the middle of the last century scientists began to detect a disturbing change in atmospheric levels of carbon dioxide. In 1957 researchers at the Scripps Institution of Oceanography, based in San Diego, California, began monitoring carbon dioxide levels in the atmosphere from Hawaii’s remote Mauna Loa Observatory located 3,000 m above sea level. When the study began, carbon dioxide concentrations in the Earth’s atmosphere were 315 molecules of gas per million molecules of air (abbreviated parts per million or ppm). Each year carbon dioxide concentrations increased—to 323 ppm by 1970 and 335 ppm by 1980. By 1988 atmospheric carbon dioxide had increased to 350 ppm, an 11 percent increase in only 31 years.
Scientists have now established that the earth’s temperature is rising. This heating process that raises the earth’s temperature is known as the global warming. It is now found that the Earth’s surface temperature rose by about 0.6 Celsius degrees over the last 100 years. Without remedial measures, many scientists fear that the global temperatures will rise 1.4 to 5.8 Celsius degrees by 2100.
It is feared that the warmer earth’s temperatures could melt parts of polar ice caps and most mountain glaciers, causing a rise in sea level of up to 1 m within a century, which would flood coastal regions. Global warming could also affect weather patterns causing, among other problems, prolonged drought or increased flooding in some of the world’s leading agricultural regions. The Himalayan glaciers would completely melt away within a period of about a century. In the process of melting new glacier lakes would be formed. Such lakes would pose serious threat to life and property of the people living in our region.
Glacier Lakes Danger to Nepal
At present glaciers are retreating in the Himalayan region, as a result, glaciers lakes are being formed. Such ephemeral lakes disrupt communication systems and various infrastructures like hydropower directly, or indirectly subjecting the mainstream to periodic catastrophic floods. Glacier lake outburst floods also produce peaks in sediment transfer.
In 1988 a joint team of Sino-Nepalese conducted the studies of the glaciers and glacier lakes in the Arun and the Sun-Kosi basins primarily in the Tibetan region of China. The Lanzhou Institute of Glaciology and Geocryology took part in the study from the Chinese side, similarly the Water and Energy Commission took part from the Nepalese side.
According to the findings of the above mentioned joint study, there are many glacier lakes in Arun, Tama Kosi, Bhote-Kosi, Trisuli, Buri Gandaki and Karnali basins within Xizang ( Tibet) of China which have some past records of the glacier lake outburst floods (GLOF) events. Sino-Nepal joint study carried out in 1988 had extensively covered only the Bhote-Kosi (Sun-Kosi) and the Arun rivers. The joint study report has recommended to conduct similar extensive studies to cover Tama Kosi and other basins also.
In 1990s Dr. Tomomi Yamada of Japan and Dr. B.P. Upadhyay, Professor of TU were involved in the study of glacier lakes within Nepal The study was conducted under the Water and Energy Commission. Their study covered Lower Barun, Chamlang Tsho, Naulekh, Sabai Tsho, Dudh Kund, Mojang, Tsho Rolpa, Duwo, Thulagi, Khyimjung and Kang Guru glacier lakes.
The glacier lakes study conducted jointly by experts from the JICA (Japan International Cooperation Agency) and WECS in 1991 provides detailed description of the Tsho Rolpa glacier lake on the end of the Trambau Glacier within Nepal in Tama -Kosi basin. The lake makes contact with the cliff-shaped glacier end, and it is covered with thick debris. This lake is extremely dangerous. The lake can be seen in a photograph presented in the report.
Glacier Lakes Outburst History
On August 4th 1985 the nearly completed Namche hydropower plant was completely destroyed by the Dig Tsho glacier lake outburst flood( GLOF). The Dig Tsho glacier was on the terminus of the Langmoche Glacier. The GLOF damaged not only the entire Namche Hydropower station but also all the bridges, trails, cultivation fields, houses, livestock along its path to the confluence of the Dudh-Kosi and the Sun-Kosi rivers at a distance of 90 km from the Dig Tsho glacier.
Since the nineteen forties, according to Sino-Nepal study, there have been at least 10 cases of glacier lake outbursts within the basins investigated. Among them there have been five bursts in three glacier lakes of the Arun River Basin, and four in three glacier lakes of the Sunkosi River(Bhote-Kosi) basin.
In Arun basin the most common are the end moraine-dammed lakes. Because the end moraine-dammed lakes mostly consist of end moraines formed in the Little Ice Age and are closer to their source glaciers, or connect directly with the glaciers, changes in the glaciers directly influence the water level of the glacier lake and the stability of the dam. At the same time, owing to the fact that the end moraine dams are composed of new and loose till, they are uncompacted and therefore unstable. This type of glacier lakes are easy to burst and cause floods and debris flows. The end moraine-dammed lakes are distributed most at the source of several short and small tributaries in the left side of the Arun River. They are distributed over a transitional zone from maritime to continental glaciers.
Gelhaipuco is an end moraine dammed lake located in the headwaters of Gelhaipu Gully ( Natangqu River Basin , east of Riwo, Dinggye County). At 14.00 on Sept. 21, 1964, the lake burst abruptly. According to the study of the Chinese Academy of Sciences, there was a heavy precipitation in the Nantangqu River Basin, which caused the glacier of the Natangqu River to slide. Huge amount of ice slid into the lake. The generated shock waves triggered the lake water to overflow the moraine dam causing the burst. There was a breach across the dam which was 30 m deep. The debris flow rushed down to the lower reaches of the Arun River in Nepal, and caused heavy economic losses
At mid-night, July 11, 1981, an end moraine dammed lake located at the headwater of the Sunkosi River suddenly burst. A breach of 50m deep and 40-60m of bottom width was formed at the moraine dam. The highest burst discharge was about 1600 cu. m./ s, which was observed 23 minutes after the burst. The high flood lasted about 60 minutes and the burst water amount was estimated at 19 million cu. m. The debris flow damaged the Kodari Highway and the Sun-Kosi Power Station in Nepal. The flood destroyed the Friendship Bridge at Kodari. According to the investigation of 1984, there had been a similar burst in 1964 from that same lake, but the burst discharge and damage caused was smaller.
Comprehensive Solution
Global warming is the main reason why the Himalayan glaciers are now retreating, and, as a result, new glacier lakes are being formed. At present the world attention is drawn to find a way to resolve the global warming problems.
Due to overwhelming scientific evidence and growing political interest, global warming is currently recognized as an important national and international issue. Since 1992 representatives from over 160 countries have met regularly to discuss how to reduce worldwide greenhouse gas emissions. In 1997 representatives met in Kyôto, Japan, and produced an agreement, known as the Kyôto Protocol, which requires industrialized countries to reduce their emissions by 2012 to an average of 5 percent below 1990 levels. To help countries meet this agreement cost-effectively, negotiators are trying to develop a system in which nations that have no obligations or that have successfully met their reduced emissions obligations could profit by selling or trading their extra emissions quotas to other countries that are struggling to reduce their emissions. Negotiating such detailed emissions trading rules has been a contentious task for the world community since the signing of the Kyôto Protocol. A ratified agreement is still not yet in force, and ratification received a setback in 2001 when newly elected U.S. president George W. Bush renounced the treaty on the grounds that the required carbon-dioxide reductions in the United States would be too costly. He also objected that developing nations would not be bound by similar carbon-dioxide reducing obligations. However, many experts expect that as the scientific evidence about the dangers of global warming continues to mount, nations will be motivated to cooperate more effectively to reduce the risks of climate change.
(Dr. Thapa writes on water resources)
