MELAMCHI PROJECT MUST BE REVIEWED
- AB Thapa
Melamchi Project to be implemented with the assistance of the Asian Development Bank must be reviewed if we want to provide free of cost the Melamchi water to inhabitants of the Kathmandu valley and at the same time to overcome to a great extent the present power shortage problem within a short period at a relatively low investment.
Positive Attitude of the ADB
In the past the Asian Development Bank had been very flexible. They fully cooperated with the Government to make substantial amendment to the agreement whenever they were convinced that there is a room to make any of the projects financed by the ADB economically and financially more viable. Kankai Irrigation Project could be a typical example.
Feasibility study as well as the detailed design of the Kankai Project was done under a grant directly by the Asian Development Bank outside Nepal. We from the Nepalese side expressed our reservation about the detailed design. After completing various formalities the Bank decided to finance the Kankai Irrigation Project. The construction of this project commenced from around the middle of 1970s.
We proposed the Asian Development Bank to amend the loan agreement by substantially modifying the total design of the project even though the contractors had already started the construction works at site. The modification allowed the capacity of various structures ( involving about 2/3 cost of the project) to be increased by about 60% absolutely without rise in project cost. The Asian Development Bank agreed to amend the Agreement. A Supplementary Loan Agreement was signed to incorporate funding for the construction of the infrastructures needed to further extend the canals and to provide services to cover additional areas.
Melamchi Tunnel Hydropower
There exists a big potential to generate cheap electricity by using the diverted flow of the Melamchi River The elevation of the Melamchi intake weir is 1715 m and the inlet to the treatment works near Sundarijal is 1409 m. Thus there is an enormously big gross head of 306 m. The UNDP feasibility study report has clearly pointed out that the net increment in investment ( the cost of the powerhouse located near Sundarijal with electromechanical equipment ) needed to implement the hydropower element is relatively small as the intake, headrace tunnel and penstock are already in place for conveying water to the treatment works. According to the feasibility report of the Arun-3 Project operating at a head of about 300 meters ( same as the Melamchi Hydropower ) the cost of electromechanical equipments and power station civil works is only about 30% of the total project cost. The UNDP study has concluded that it would be worth constructing the hydropower and it could make a contribution to reducing the cost of drinking water to Kathmandu. The UNDP report explains that even before the diversion of the Yangri and Larke rivers the total annual generation of the Melamchi hydropower would be 60 GWh and out of it the firm power generation would be 40.5 GWh.
The Melamchi hydroelectricity generation would be close to 50% of the annual generation of the Kulekhani No.1 hydropower project. After the diversion of the Yangri and Larke the electricity generation of the Melamchi hydropower plant would have been further increased.
It is quite unfortunate that sometime back the hydropower component of the Melamchi Project was dropped ignoring the strong recommendation of the UNDP report. It is still not too late to reintroduce the hydropower component.
Additional Use of Melamchi Tunnel
The 28 km long Melamchi tunnel to divert the Melamchi water into the Kathmandu valley is the most expensive component of this project. This tunnel, apart from diverting Melamchi water into Kathmandu valley, could be developed as a trunk tunnel to provide transit to regulated flow of the Langtang river, and also the waters drawn from the Yangri and Larke rivers. Such conversion would not involve additional investment. A small portion of the combined flow of these rivers sufficient to meet the long term demand for water in the Katmandu valley could be provided for free after the generation of electricity at hydropower station located near Sundarijal. The bulk of the water could be dropped into the Kulekhani reservoir to generate abundant cheap electricity. Water thus pumped into the Kulekhani reservoir after being used for power generation in a cascade of hydropower stations (Kulekhani Nos 1,2 and even 3) could also be used to provide gravity irrigation in Chitwan valley
The Langtang Power Projects
The Langtang projects operating at a head of about one thousand meters and more could produce electric energy at a very low cost . Apart from it, water in abundant quantity could be supplied to the Kathmandu valley for free. The concept of the Langtang project solely for power generation was developed under the UNDP supported Gandak basin masterplan study . This concept requires some revision to include a new component to supply drinking water to Kathmandu valley. It necessitates dropping the regulated Langtang water at the end into the Melamchi river instead of the Bhotekosi (Trisuli).
According to the Gandak Basin Master Plan a 120 m high dam has been proposed on the Langtang Khola near Jaithang. The volume of the reservoir would be about 180 million cubic meters. Based on revised concept the water in the reservoir at a full supply level of 3995 meters would be first tapped by the Langtang-1 power station operating at a gross head of 950 meters. The installed capacity of the Langtang-1 power station located near Ghore Tabela about 15 km downstream from the storage reservoir would be about 70 MW.
Water from the Langtang-1 power station would be directly drawn into the Langtang-2 power station. For augmenting this flow the water from the catchment downstream of the storage dam would also be drawn into the headrace tunnel of the Langtang-2 power station. The installed capacity of the Langtang-2 power station operating at a head of about 1300 meters would be about 150 MW.
Why is Langtang Power Cheap?
Of all the site characteristics, head is the most important. Design guidelines, 1989 approved by the American Society of Civil Engineers has given some simple reasoning that would help to explain why the super high head Langtang power stations operating at many times greater head by comparision with other hydropowers could be built at very low cost. "Very simply if one doubles the head the quantity of water needed to produce a certain amount of energy is halved, Thus, for like site energy development the penstock area and reservoir volume are halved and further large cost reductions occur for powerhouse and machinery costs. This fundamental consideration is at the root of the large cost reductions that occur at higher heads."
A joint team of German, Japanese and the US consultants has made an interesting reference to a Canadian high head project vis-à-vis the Upper Arun project to be operated at moderately high heads. "It is worth mentioning that the search of the worldwide inventory of the existing hydropower installations identified only one plant with a combined head and flow magnitudes greater than that of the Upper Arun - Kemano in British Columbia, Canada". At present the electricity generated by the 896 MW Kemano Project with a 16.3 km long headrace tunnel operating at 800 m head provides power for Alcan's aluminum smelters at Kitimat at a cost below US cents 3 per KWh.
