Comment to the Article

"Threat to Super High Head Langtang Projects" by Dr. A. B. Thapa

Dr. A.B. Thapa published an interesting and thought provoking technical article in the August 16, 2002 issue of Spotlight magazine entitled "Threat to Super High Head Langtang Projects" in which he provided his insight and thoughts on the integrated water resources planning and development for the Langtang, Melamchi and Kulekhani rivers. The rivers are the sources for large, complicated and successive transbasin diversion projects. These projects criss cross the country from the most Northern point to the Southern borders of Nepal. His theory lacks consideration of technical, economical and socio-political realities. Let us take a realistic look at his theories in comparison to actual conditions. The Gandak Basin Master Plan Study identified the hydropower potential of the Langtang river based on the initial head and assumed discharge data available at different locations along the river. The proposed high dam at Jaithang for Langtang-1 would have to be approximately 300 m high to realize the suggested full supply level of 3,995 meters (amsl). At this altitude the backwater level would reach the tongue of Langtang glacier which would cause the reservoir to contain ice particles most of the year. The back water level would directly threaten the existence of the glacier and could have a disastrous impact on the ecology of the World famous Langtang National Park. The 30 - 40 m thick loose moraine deposit underneath the dam renders the proposition of a high dam technically and economically impractical. The river gradient at the dam location is very steep and the assumed 180 million m3 storage capacity (compared with 7.4 million live storage of Ghodatabela) site is not a very realistic figure. The minimum measured flow of the river, 15 km downstream at Ghodatabela (3,000 m/amsl), is below 4 m3/s and the average annual flow calculated by the Nepal Electricity Authority (NEA) is approximately 10-12 m3/s. Therefore, the average annual flow at 4,000 m amsl would be substantially less than the 10 m3/s, instead of 15m3/s mentioned in the article. Since, between the 3,995 m elevation and the Ghodatabela there are several smaller tributaries that join the river. Hence, the generation figure would be much less than the 70 MW mentioned. Concerns on environmental impacts and consideration of the technical and economical factors for this site indicate further studies would be wasted and of no practical use.

The Langtang-2 storage project, dam site located at Ghodatabela (3,000 m amsl) with a very high (1,570 m gross) head is an excellent medium sized storage project identified by NEA after pre-feasibility level studies of several alternatives. Preliminary design shows there is a cumulative 12 km long 5 drop shafts cum horizontal pressure tunnels and 93 m high dam with 7.4 million m3 live storage capacity. The project is designed to have a 218 MW installed capacity. It yields 950 GWh per annum with 304 GWh dry season energy and specific energy cost is forecasted to be approximately 3.85 cents/kWh. The tail water of the Langtang-2 is dropped in the Bhote Koshi river at an elevation of 1,421 m amsl. (for more information refer Nepal Electricity Authority, Fiscal year 2001/02 - A Year In Review.

The issue raised here is that if you direct the Langtang river flow to Melamchi basin from Ghodatabela, you would then need to have an approximately a 22 km long tunnel crossing the National Park from west to east and impinging on the fragile ecology and geology of the area which could have unknown impacts. The generation cost per unit for this alternative would be substantially higher than 4 cents/kWh compared with the unsupported 2 cents/kWh stated by Dr. Thapa.

The Mini Langtang Project on the tailend of Langtang-2, is licensed to a Private Developer. It is a 14 MW project with a 200 meter head. This project, still being considered would overlap with Langtang-2. With the full development of the bigger project, this mini project may well be bought back by the other developer.
The theory offered that with the Langtang Diversion, the Melamchi Tunnel would be expected to run at full capacity of approximate 15m3/s throughout the year and generate 35 MW power is simply not true. During the dry season (January - April) the maximum flow in the tunnel would only be 8 - 10 m3/s and would generate 15 - 20 MW power. If this option is to be considered, then the suggested power could be generated right in the Melamchi Valley itself without any need to divert the river flow to the Kathmandu Valley.

The question of water supply to the Kulekhani river is a difficult one. The difference in elevation between the Kathmandu Valley (1,430 - 1,450 m) to the Kulekhani Reservoir with an elevation of 1,530 m is approximately 100 m higher. In addition to about 15 km surface channel, it would necessitate a pump station to lift water and a further 13 - 14 km of tunnel for diversion or extra tunnel caverns are needed to go round the valley mountains. It would add a further 10 to 15 km to the tunnel length. Technically, this can be done. The Kulekhani reservoir is designed to accommodate the full flow of Kulekhani river water and generate 60 MW of power. If it is necessary to increase the capacity to generate an extra 300 MW power, dam height must be increased. Environmentally, technically and economically these issues require to be seriously studied. A separate parallel tunnel to divert the additional water and new power house would be needed. The current Kulekhani Project does not have the capacity to handle this added burden. The old system would have to be dismantled and a new system constructed.

Analysis of Dr. Thapa's proposal shows that after traversing close to 100 km of terrain mostly utilizing underground pressurized water conduits would produce a gross total head of less than 2,300 m. Ghodatabela, at an elevation of 3,000 m, is the highest point technically and economically feasible for the diversion of Langtang water for a detoured journey to the Hetauda at an elevation of approximately 700-800 m. Recent hydrological information shows that the annual average diversion discharge is not more than 10 m3/s (refer recent NEA studies). Assuming a net head of 2,000 m and an average annual flow through the turbines of 10 m3/s could produce a maximum of approximate 175 MW base load with a continuous generation capacity of 1,534 GWh of energy. Considering the significant cost for generation of this energy, the idea of providing cheap or almost free drinking water to the Kathmandu Valley at the cost of the electricity is nothing more than a dream. Please remember that Langtang 2 is already under consideration and estimated energy yield is 950 GWh.

The another serious issue raised by Dr. Thapa was "Inhabitants of the Valley, however, are unaware that they would have to pay a monthly bill of about Rs. 4,000 at present price levels after the Melamchi Project" which is not based on the actual facts and is totally incorrect. If all financing for the Melamchi Project and related components were to be passed on to the Kathmandu Valley Water Utility (KVWU) as loans, then the tariff would be approximately NRs. 57/m3 in 2007 (at 2000 prices) to meet operating costs and debt servicing at an interest rate of 8%. The minimum level of Project cost repayable by KVWU is likely to be only 50% with the balance booked as a Grant. In this event the financial analysis allows for a tariff of Rs. 25 /m3 to meet full debt service in 2007 (Refer Melamchi Project, Financial Analysis, Nov. 2000). Therefore, the average tariff level to be set in the post Melamchi scenario is estimated to be between NRs. 26-28/m3. This allows that for a medium income family consisting of an average of 5 members would be paying approximately Rs. 560 as a normal monthly tariff for their water consumption.

The theories of Dr. Thapa although interesting are not based on actual considerations and need to be more properly studied and supported with more accurate facts and figures than was presented in the article.

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