Implementation of the proposed run-of-river type 900 MW Upper Karnali Project would be extremely harmful to Nepal’s western terai irrigation and it would also ruin the prospect to supply abundant cheap peaking energy to India badly needed there to supplement energy generation from their coal fired, combined cycle and nuclear power stations which can not be economically operated to meet the demand for peaking. The proposed hydropower to meet the demand for three hourly sharp peaking energy without reregulation immediate downstream would lead to very serious land sliding, bank erosion, retrogression and other types of flooding problems. There is a far better alternative solution.
Energy Export to India
The 4180 MW mega storage project and the proposed 900 MW run-of-river project are two variants of the same hydropower project to be built at the Karnali bend site acclaimed for generation of cheap electricity. Originally the capacity of the run-of-river variant was only 240 MW but recently it has been raised to 900 MW to meet the demand for peaking in India. Despite these differences the annual firm energy generation of both these variants would be exactly the same which is estimated to be just about 1000 GWH.
In contrast to a mere 1000 MWH annual firm energy generation by the run-of-river type variant, the annual firm energy generation of the 4180 MW storage project would be about 9000 MWH. Thanks to extremely favourable topography, the peaking energy generation cost of the Upper Karnali storage project operating at a head of about 400 meters is expected to be exceptionally low not only in comparison with that of its run-of-river type variant but also in comparison with other mega storage projects like the Kosi Dam Project and Karnali (Chisapani) Project operating at a head of just around 200 meters. Nepal would be able to supply abundant cheap peaking energy to India if the 4180 MW storage type Upper Karnali Project is implemented.
The firm installed capacity of the Upper Karnali storage project could be raised even further up to 8000 MW if the peaking hour is limited to daily 3 hours as in case of the proposed 900 MW variant. The increase in installed capacity to 8000 MW could greatly facilitate to improve the energy supply situation in very big areas of India’s northern grid which is mostly depend on thermal generation.
We should not shut our eyes while taking final decision on implementation of the Upper Karnali Project to the fact that we will have to completely decommission the 900 MW Project if we want to implement in future the 4180 MW Karnali Storage Project . It has been clearly explained about it in the World Bank financed detailed prefeasibility study report of this project.
Disastrous to Existing Irrigation in Nepal
The designed discharge of the 900 MW Upper Karnali Project is expected to be about 750 cumecs and the 90% probable discharge of the Karnali river at Upper Karnali project site is only 97.6 cumecs. According to the data recently published in a local newspaper there are already three irrigation canals drawing water directly from the Karnali to irrigate 57.5 thousand hectare lands. Those canals in the absence of diversion barrage and proper regulating structures must be having very low conveyance as well as irrigation efficiency. If the crop grown in summer is paddy, the water requirement could be as high as 2 litres per hectares. Thus the total diversion from the river could reach up to 100 cumecs though a substantial proportion of this flow would come back to the river immediately downstream in the form of regeneration due to high seepage and other losses.
Bheri river is soon going to be diverted into Babai river. If the limited flow from the West Seti river is not considered the water supply to existing Karnali canals would be completely cut off for 21 hours each day during dry season after the completion of the proposed 900 MW storage project. This will have disastrous consequences for agriculture.
The proposed hydropower to meet the demand for three hourly sharp peaking energy without reregulation immediate downstream would lead to very serious land sliding, bank erosion, retrogression and other types of flooding problems. Possible retrogression of the river bed could greatly hamper full entry of water into irrigation canal intake.
The Alternative Solution
It would be better not to implement the run-or-river type Upper Karnali Project. However, a very low cost variant of this project could also be considered for implementation in near future to resolve our present energy shortage problem if there is going to be a very long delay in implementation of the storage type project.
A simple 120 MW run-of-river type hydropower without the provision of daily storage could be the best option for the time being. This project would be decommissioned later on when we intend to implement the storage project. The low cost floating type weir of that project could be later on used as coffer dam and the power tunnel for temporary diversion during the construction of the storage project.
The proposed 120 MW small Upper Karnali Project would also be able to generate 1000 GWH firm energy annually as much as the 900 MW variant though it would be mostly to meet the demand for base load. This project must preferably be built by the government itself for greater flexibility in taking any type of appropriate decision in future.
Comparative Investment Cost
The proposed 120 MW Upper Karnali Project with a very short headrace tunnel just 2.5 km long and a simple floating type weir might be able to generate three times more firm energy during the dry months when we are facing acute energy shortage than the existing 144 MW Kaligandaki A hydropower with a very complex regulating barrage and relatively a long headrace tunnel. The investment cost of the proposed 120 MW Upper Karnali project could be only half of the latter.
The demand for cheap energy to meet the base load would remain unfulfilled even after completion of the projects like the Upper Tama-kosi. The proposed 120 MW project could be quickly implemented by our Government to provide immediate relief for our people from the present power shortage crisis at relatively a very small investment. Moreover, the proposed 120 MW hydropower would not have any adverse impact on irrigation in Nepal.