NEPAL FOR WHITEST OF WHITE ELEPHANTS: BEST HYDROPOWER OPTIONS IGNORED
- Dr. A.B. Thapa
At present our country is reeling from extreme shortage of electric power. Most of our industries are on the verge of collapse. People are facing great hardship due to daily 12 hours long load shedding. Concerned authorities have warned that the load shedding duration will be further increased and it will go to daily 16 hours. A state of power shortage emergency has already been declared.
Nepal is now facing acute power shortage problems despite the fact that we have at our disposal a wide range of hydropower projects and some of them could be ideally suited to resolve our present power shortage crisis. We never seriously cared to worry about our own problems. We are more concerned to please foreign multinational companies by handing them over the most lucrative hydropower projects. As a result, we are now pushed to an extreme desperate situation. It has now started to cross the mind of some of our decision makers that the introduction of diesel power plants on a gigantic scale is the only solution to end the present power shortage crisis.
White Elephant
Various agencies are floating their ideas to resolve the present power shortage crisis. Among them the idea to build immediately a 200 MW diesel plant has drawn everybody’s attention. Most of the Nepalese will not disagree that the proposed diesel plant would be the WHITEST OF THE WHITE ELEPHANTS for a poor country like Nepal. Unfortunately, our Government has not yet truly bothered to identify proper solution to resolve present power shortage crisis. There can be several options which have not yet been explored. As explained hereinafter the development of the Upper Karnali project is the most appropriate answer to expeditious resolution of the present power shortage problem.
Why Upper Karnali Best?
Extremely favourable topography of the run-of-river Upper Karnali project allows to upgrade this project virtually to the category of the best storage dam type projects. A narrow mountain on the project site is acting just like a high dam. As a result, there is a drop in elevation of about 150 meters. There is also a quite large minimum flow of the Upper Karnali near the intake site, which is around 100 cum//sec. Undoubtedly the Upper Karnali project is extremely attractive for generation of cheap energy particularly during the dry seasons.
Normally the investment cost of the high dam would be quite high if we want to prefer to have purely a high dam project to resolve the present dry season energy supply problems. Let us take the case of the Kankai High Dam Project. According to feasibility report of the Kankai High Dam Project the cost of the high dam was going to be two times greater than the cost of the hydropower station including its power station related civil works.
Short Construction Period
Construction period of the Upper Karnali project would be quite short by comparison with other projects earmarked to supply power mostly during the dry seasons. Hydropower projects greatly rely on high dam to store water for to generate enough power during the dry months. It takes a very long time to build a high dam. The construction period of the Upper Karnali project is going to be significantly short because this project does not need to have a high dam. On top of it the construction period of the power tunnel would also be quite short because its total length is only about two kilometers.
Development in Stages
The Upper Karnali run-of-river hydropower project can be developed in the following 3 steps. We can implement the whole project in one go or in more than one stages depending upon our demand for power and availability of funds:
(1) Without a diversion structure (2) Weir ( without gates) (3) Barrage (with gates)
Cheapest and the Quickest
Diversion of the Karnali with or without a weir is certainly the cheapest option to generate electricity. We would be able to implement such project within a short period particularly the one directly drawing the Karnali water without building a diversion structure. The proposed project can be planned to generate almost 100% firm energy. It can greatly help to minimize the power shortage constraint badly affecting the smooth supply of electricity during the dry seasons. The power station will be able to produce exclusively firm energy in contrast to other hydropower stations already in operation in Nepal that generate electricity mostly in monsoon season whereas they are able to produce far less electricity during the dry seasons when the demand for electricity is the highest.
There can be one major disadvantage in adopting this type of plan to draw water for power generation without building a weir. We may not be able to draw the entire dry season flow of the river. We might have to leave behind a significant proportion of the dry season flow of the river to control the entry of the sediments into the power conduit.
Diversion Without a Weir
We can partially use the dry season flow of the Karnali to generate electricity by drawing water into the headrace tunnel without building a weir. The 90% probable discharge of the river at Upper Karnali site is about 100 cumecs. We might be safely able to draw for power generation about 50 cumecs flow during the dry season, and the rest of the flow will keep the river channel clear by sluicing out the sediments away from the vicinity of the power tunnel intake. However, the whole plan must be tested in a physical model. Department of Irrigation had conducted with the help of delft hydraulics of Netherlands at the Asian Institute of Technology Bangkok, Thailand in 1992 the model test to build an intake structure directly drawing water from the Kosi without building a barrage or weir. Water drawn directly from the Kosi is first used for power generation; thereafter it is used for irrigation. The topographical condition of the project at Chatra is quite unfavourable. Sediments drawn through the intake into the desanding basin are dredged and pumped back into the river. It is not possible to flush out the sediment under gravity because the river bed level is higher than the bottom of the desanding basin. In case of the Upper Karnali the sediments can easily be flushed out under gravity into the Karnali from the desanding basin located at the far end of the headrace tunnel.
Electricity in Dry Season.
The total installed capacity of the Upper Karnali project (without a weir) could be about 60 MW if we want to use only up to 50% dry season flow of the Upper Karnali. Such hydropower station will be able to produce electricity in dry season about two and a half times more by comparison with the generation of the Marshyangdi Hydropower project, which is now in operation. Similarly the installed capacity of the Upper Karnali (with a weir) could be about 120 MW if we want to use 100% dry season flow. Such hydropower will be able to produce in dry season electricity five times more by comparison with the generation of the Marshyangdi project.
