Nepals total hydropower potential Update requirement

The first ever elected government of Nepal after the People’s Movement in 2062/63 put forward a target of developing 10,000 MW of hydroelectricity in 10 years. In doing so, it ratified some of the existing rules and regulations. Increasing the license fees, decreasing the period of survey license, waiving projects below 50 MW from mandatory environmental impact assessment, etc The present government has gone a step further and has targeted 25,000 MW in the next two decades. All this is very encouraging for the people who are engaged or intend to become engaged in the hydropower sector. It also very important for the overall development of the country because enhanced hydropower could lead Nepal to the utmost heights of development. Nepal is a Himalayan country with many rivers and streams which could easily yield thousands of megawatts of hydroelectricity. However, there is a question as to how much electricity could be generated if all rivers of Nepal are used for the purpose? The need arises to find reliable and justifiable answer to this question.

In 1966, i.e. 43 years ago, Dr. Hari Man Shrestha assessed the total hydropower potential in Nepal as 83,500 MW. He did so during the research work for his Ph.D. Since then, no further study has, so far, been done in this field. And, that finding seems to have been accepted as full and final to date. Much water has flown down river Bagmati during these four decades, and the world has seen sea changes in the fields of science and technology. Moreover, the revolutionary changes in the fields of computer and information technology has helped find new dimensions in research and study approaches and many findings of the past have been proved wrong in recent years. But, in Nepal, not much initiative has been taken to carry out further investigations and research works to justify the findings of Dr. Shrestha. This probably could be due to the lack of research-friendly atmosphere here. For most of the time during these past four decades, Nepal has seen either an autocratic regime in the form of Panchayat system or the processes of revolutionary changes in quick successions. However, after the successful culmination of such processes and at a time when hopefully the country is going to complete the drafting of the people’s constitution, it is high time to initiate new research and study works in the field of hydropower as well. This is important because of certain complications in planning and execution of hydropower projects due to the lack of reliable information. For example, Dr. Shrestha put the total hydropower potential of Nepal as 83,500 MW but there are already projects totaling 96,000 MW awaiting issuance of survey license at the Department of Electricity Development.

A team of researchers including Rupesh Shah and Sudip Prakash Adhikari led by the author of this article at the Institute of Engineering, Pulchowk Campus, has recently carried out a basic research work in this field. The team has attempted to assess the total hydropower potential of Nepal using modern day technology. In the process ArcGIS, a mapping tool used worldwide and Hydropower Model, a software, specifically developed by the author for this purpose using FORTRAN LANGUAGE, has been used.

In the research, the observed monthly discharge (river flow) data of 10 years (1997-2006) are processed and design discharges at different percentile are calculated. The SRTM (Satellite Radar Topographic Mission) Digital Elevation Model is used as basic input to GIS software. The hydropower model takes the input of DEM, River Network, Elevation of river, Flow Accumulation and stream Order in ASCII format, processed in GIS software. The model calculates the head, i.e. the height difference between the intake site where water is diverted from the river and the powerhouse where electricity is generated, and discharge using the monthly normalized discharge and catchment area and finally calculates the potential power as well as energy.

The outcome of the research is rather surprising. Gross installed power potential and total annual energy of Kanakai, Koshi, Bagmati, Narayani, Rapti, Karnali and Mahakali are 241 MW, 17,008 MW, 424 MW, 17,800 MW, 438 MW, 15,661 MW, 2261 MW and 1517 GWh, 10,8816 GWh, 2574 GWh, 113,373 GWh, 2951 GWh, 102,324 GWh, 14,980 GWh respectively. The total installed power and annual energy of Nepal is estimated as 53,836.00MW and 346,538.00 GWh respectively. Thus, in a way it could be concluded that approximately 54,000 MW is the maximum hydropower that Nepal could get from all of its rivers considering 40 percentile discharge in wet season. The potential is more with dams like Kulekhani.

The ROR potential of 53,836 MW, as estimated by the author and his associates, could be considered as the basic potential without considering environmental discharges, etc. Nepal’s total hydro potential with all types of schemes will thus include this ROR potential and the variable storage potential presently under study by the author and his associates.

Dr. Jha is currently associated with Pulchowk Campus, IOE, TU