Uncertainties About Upper Tama-Kosi Project
AB Thapa
Amid much fanfare sometime back the signing ceremony of the MoU to provide Sanchaya Kosh loan to the NEA to implement the Upper Tama-Kosi project was accomplished. Ministry of Water Resources is now saying that the load-shedding will continue until the completion of the 309 MW Upper Tama-Kosi project. The announcement of the NEA has greatly disappointed those who like to see quick end to present power shortage crisis.
There are few critical issues very important to resolve the present power shortage problems. (1} Are we paying due attention to proper maintenance of the existing hydropower projects and strict adherence to dates earmarked for the completion of the projects under construction? (2) Have we explored all possibilities to expand the capacity of the existing hydropower projects at least cost and time to significantly enhance the generation? (3) Can the 309 MW Upper Tama-Kosi project be considered a dependable project to fulfill the need to solve the present load-shedding problem.
Proper Maintenance
It appears according to newspaper reporting that the present deep cut in power supply has been resulted from the complete shut-down in operation of the Kulekhani No 2 project. It is reported that the shut-down of the hydropower was necessitated to carry out repair and maintenance works of the electromechanical equipments. Unfortunatyely it is not a proper time to conduct maintenance and repair works requiring suspension of the operation. At present the power demand is at the peak, whereas the capacity (KW) is greatly reduced ( not necessarily energy KWh).
Kulekhani No 1 and Kulekhani No 2 operate in tandem. Due to lack of adherence to proper operation and maintenance procedures we are now compelled to spill the scarce regulated flow of the Kulekhani river earmarked for the operation of the Kulekhani No 2
Project Under Construction
The Middle Marshyangdi project is the biggest among the hydropower projects under construction at present. The impact of present load-shedding would have been far less severe if this project would have been completed in time. It might not be wrong to say that the construction of this project is in a state of total neglect. Ministry of Water Resources and other branches of the Government such as the Planning Commission must regularly visit to provide necessary supports to those directly involved in the construction works.
Expansion of Kulekhani Hydropower Generation
It might be possible almost to double the generation of the Kulekhani Nos 1, 2 &3 hydropower stations by pumping water drawn near Chobar into the Kulekhani storage reservoir. The total cost of such diversion could be only about US $ 25 million. The value of additional annual power generation at the price of US Cents 6 could be about US $ 12 million.
At present the average annual flow of the Bagmati at Chobar is about 15 CUMECS. The monthly average flow in seven months from June to December is over 4 CUMECS. In the rest five months from January to May the average flow is 2 CUMECS. We might not be wrong to assume that we would be able to divert enough Bagmati flow into the Kulekhani reservoir to supply average annual 4 CUMECS flow to Kulelhani hydropower stations
The diversion of the surplus Bagmati water from Kathmandu valley to the Kulekhani reservoir could be a very simple and at the same time the most cost effective proposition. The NEA can easily build this scheme at its own cost. The entire construction works can easily be completed within three years.
We might have to build a 15 MW pump station at Chobar to lift 4 cumecs water to a height of about 300 meters which might be equivalent in height to the full supply level (FSL) of the Kulekhani storage reservoir. It is equally possible that instead of one big pump station we might need more than one pump station with a total capacity of about 15 MW depending on nature of topography. A 15 km long waterway might be needed to carry the water into the Kulekhani storage reservoir out of it the length of the tunnel could be about 9 kilometers.
Melamchi and Langtang Diversion
If the whole plan of diversion of the Langtang, Melamchi and Bagmati into the Kulekhani reservoir as laid down in the WECS study reports is implemented, it would be possible to generate about 2,500 GWh additional electricity at the cost of only about US Cents 3 per KWh. The combined diverted flow of the Langtang, Melamchi, Bagmati and Kulekhani will significantly augment the dry season flow of the Rapti river, which can be used to increase the area under gravity irrigation in Chitwan valley.
Schemes on the Tama- Kosi River
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 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.
We may need the cooperation from the Chinese side to conduct study related to GLOF. Such study would be necessary to design vital structures. Apart from it we may need to set up monitoring mechanism for early warning. The conclusion of the Arun-3 feasibility report is presented here “ It is indispensable to have close cooperation from China in the area of surveillance of GLOF prone glacier lakes and monitoring river flow in its territory”. All these are time-consuming works.
Actual Project Cost Could Be High
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 originally 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.
In case of the 60 MW Khimti project operating at exceptionally high head of about 650 meters the estimated construction cost according to the feasibility study report of the NORPOWER was only US $ 60 million. The NEA found that the estimate is not accurate. The revised estimate of that project is US $ 150 million, which has been applied to determine the purchase price of the electricity by the NEA from the developer of that hydropower.
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.
Nepal Hard Hit by GLOFs
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.
In Conclusion
Upper Tama-Kosi can be an attractive hydropower project. However, we must conduct a through study of this project before we take decision to implement this project. The study can take quite some time since at certain stage China’s involvement might become necessary.
