VOL. 27, NO. 36, May 23, 2008 (Jestha 10 2065 B.S.)

AB Thapa

It has been reported in local newspaper Kantipur  dated May 15, 2008 that  the Chief  Executive Officer of the Himalayan Bank has announced the decision  to finance on the request of Nepal Electricity Authority six billion rupees in construction of the Upper Tamakosi  Project. It is a well known fact based on  information provided by Chinese to Water and Energy Commission that the proposed Upper Tamakosi Project is very close to major glacier lakes located further upstream of the project site inside the Chinese territory. There is a need to conduct a thorough study to insure that we may not have to face again the terrible situation similar to the one that resulted from  the GLOF ( Glacial Lake Outburst Flood)  when  the newly built  Namche Bazar Hydropower  was completely wiped  out without a trace.  It is also necessary to verify thoroughly the final cost estimates of this project to prevent later on  huge jump in project cost giving due consideration to bitter fact that the NEA tended in the past  to approve blindly the project cost estimates if they  were endorsed by foreign engineers regardless of whether they are adequately experienced or not.  

Upper Tama-Kosi Project

The Tama- Kosi River is the second largest tributary of the Sun -Kosi River. Originally 6 hydropower stations in a cascade were planned.   

The Tama-Kosi No.6 according to the Kosi basin Master Plan is the uppermost project.  The intake of the  proposed Upper Tama-Kosi Project is said to be further  to the north  close to the China-Nepal border. This  reach of the Tama-Kosi  is very close to places in  Nepal  and Tibet where very dangerous glacier lakes are located.  Thus, any GLOF incidence would have left in its wake the most horrific destruction  on this stretch of the Tama-Kosi. 

The 309 MW Upper Tama-Kosi Hydropower project is surrounded by much doubts  about  the  completeness of the  study to justify to take the decision to go for its implementation in immediate future. It appears based on  previous studies of other similar projects that the proposed Upper Tama-Kosi project might be entangled in few other serious technical problems also.  

Glacier Lakes Dangerous For Nepal

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  past records of the glacier lake outburst  floods (GLOF) events. The joint study report has recommended to conduct  extensive studies to cover Tama Kosi and other basins also.  

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.  This glacier lake is extremely dangerous.   

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).  

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  basin.  

Gelhaipuco is an end moraine dammed lake located in the headwaters of Gelhaipu Gully (Natangqu River Basin , east of Riwo, Dinggye County) in Arun basin.   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.  

Dam Height Could  Be Much Higher

The bed slope of the  Upper Tama-Kosi is expected to be extremely steep. A very high dam is needed to provide a daily storage reservoir adequate in volume.  JICA study under the Kosi Basin Master Plan had ruled out the possibility to provide daily storage pond to serve Tama-Kosi-5 and Tama-Kosi-6 projects. We have learnt  from  our past Arun-3 Project planning experience that  the provision of a  daily storage reservoir by damming the river course itself in case of the rivers like the Arun or Tama-Kosi  is going to be  extremely  difficult task that would certainly involve a huge investment. In case of the Arun-3 Hydropower Project, it was planned that a dam only 20 meters in height would suffice to provide daily storage pond but at the final stage we had to raise the height to 65 meters.

Accuracy of Cost Estimates

It is very important to know about the accuracy of the cost estimate before making a final comment in favour or against any project. Unfortunately the bitter past experience of  blindly believing  in  the manipulated cost estimate of  the Khimti Hydropower is still fresh in the minds of Nepalese people. An unacceptable level of inaccuracy in cost estimate of the 60 MW Khimti Hydropower project had forced our country to buy electricity from the private developer based on a very high  US $ 140 million revised  cost of that project though the original cost of the project based on the feasibility study carried  out  by the NORPOWER just before the commencement of the construction was only US $ 60 million.

In Conclusion

It is hoped that the Himalayan Bank will not  put  the hard earned savings of their depositors in jeopardy by  taking the decision in haste to  finance  the construction of the Upper Tama-Kosi Project without  a thorough study.