Quickest Cheapest and Easy Way to Solve Power Shortage Crisis
UPPER KARNALI DEVELOPMENT IN STAGES
AB Thapa
The Upper Karnali project is uniquely suited to serve the best to resolve our present power shortage crisis. This project can be developed at an astonishingly low cost to produce abundant firm energy during the dry months when our demand for electricity is the highest. Initially this project can be developed at the cost of only about US $ 150 million to produce in dry months firm energy two and a half times more by comparison with the energy generation of the Marshyangdi project. In future the firm energy generation can be doubled by providing new structures at an additional cost of about US $ 100 million.
Deepening Power Shortage Crisis
At present our country is reeling from deepening power shortage crisis. It is not just the prolonged countrywide daily load-shedding that has made the life of our people miserable. Worst of all, our industry, commerce, tourism and every other sphere of economy have already started to be badly affected. Needless to say that we are heading for a big economic disaster. Our country will greatly suffer if we failed to address satisfactorily the present power shortage problems without much delay. Unfortunately, the present power shortage crisis is getting worse and worse. There are not as yet good signs to be assured that we are going to overcome our present difficulty of power shortage in foreseeable future.
There is a great urgency to identify at least one medium-sized hydropower project comparatively cheap at the price and which can be implemented within a very short period to minimize the adverse impact of growing power shortage. It is attempted to explain in this brief article how under present circumstance the implementation of the Upper Karnali Project in stages can be the best choice to resolve the present deepening energy crisis.
Why Upper Karnali?
The topography of the Upper Karnali project has a unique feature that provides an excellent opportunity to dispense with the need for costly structures like the high dam to generate electricity on a moderately big scale. The narrow hill, that separates the upper and lower courses of the Upper Karnali flowing in directions opposite to one another, acts just like a high dam. The cross-sectional width of the hill is only slightly over 2 kilometers. Thus the Upper Karnali Project waterway starting from the intake of the headrace tunnel to the end of the tailrace will almost be the same in total length as the one needed for a purely high dam project. In case of the Karnali Chisapani high dam the total length of the waterway is also about 2 kilometers.
Very High Hydropower Potential
The Karnali river makes a big loop in its lower reach near a place called Asare. From here the river flows in the south-east direction for about 25 kilometers, after that the river makes a complete reversal in its direction. The river comes back to a point just two kilometers away from its earlier position near Asare. There is a drop of about 150 meters in Karnali river bed elevations between these two positions merely two kilometers away from one another The project to utilize this bend for power generation is known as the Upper Karnali Project. . There are very good sites to build a large storage dam at the beginning of the bend. Thus, it makes the Upper Karnali Storage Project far superior to the 10,800 MW Karnali Chisapani Project in terms of per unit capacity investment cost because its hydropower station would be operating at a firm head two times greater than that of the latter though the total length of the waterway of both these hydropower plants would be almost exactly the same.
Development in Stage
The Upper Karnali hydropower site can be developed in the following 4 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) (4) High dam.
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While drawing a plan to implement the hydropower project at Upper Karnali site, we should not let the conclusion of the past pre-feasibility study that the high dam alternative and the first three alternatives are mutually exclusive slip our memory. Thus, it would be desirable to give preference to the alternative involving less investment.
Cheapest and the Quickest Option
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 to draw water directly from the Kosi river at Chatra 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 Generation 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.
Project Cost and Construction Period
According to the 1989 pre-feasibility study report conducted with the financial assistance of the World Bank the cost of the 240 MW Upper Karnali project was estimated at US $ 250 million. This cost is exclusive of transmission and approach road costs. The present cost of the above proposed 60 MW and 120 MW alternatives of the Upper Karnali project based on 1989 pre-feasibility estimate exclusive of transmission and approach road costs could be about US $ 250 million and US $ 150 million respectively. It can roughly be said at this stage that it will take about 3 years to complete the construction of 60 MW alternative whereas 4 years for the 120 MW.
Compatibility with Mega Upper Karnali
Upper Karnali high dam project and other three above described alternatives are mutually exclusive. Thus, instead of a high cost barrage type alternative, it would be desirable to select for implementation one of the two low cost alternatives to minimize loss arising out of closure of the project if we foresee that the high dam project will be implemented within the life time of the barrage type alternative.
