Lower Subansiri Hydro Electric Project
Lower Subansiri Hydro Electric Project
Lower Subansiri Hydro Electric Project
The country's per capita consumption of electricity (PCCE) is about 631 Kilo watt hours (kwh) whereas the per capita consumption in the Northeast is 222.602 kwh. However, as the pace of development in Assam increases, demand for equivalent power is also picking up. In 2005-2006, the state's requirement of electricity was only 4261 million units (MU) whereas only 3537 MU was available. But the PCCE of Himalayan States of India such as J & K, Himachal, Uttranchal and Sikkim it is about 640 kwh which is greater than India's PCCE. It is in this perspective that the controversy over the Lower Subansiri Hydro Electric Project (LSHEP) should be seen. Unfortunately, the project has created much concern among different sections of people even though the latest methodology and technology for setting up a favourable hydropower are now available in this world. This output of this technology will be more perfect while advance remote sensing & GIS techniques is used in the relevant fields of water resources engineering, upstream and downstream hydrology along with environmental engineering assessment.
The controversial LSHEP has agitated the minds of the people of Northeast India particularly in Assam as the downstream area of the project falls in the northeast part of the state. Sections of people have justifiably protested the project's feasibility and also its impact on the downstream areas. The people's concern got a filling when an expert group committee report pointed out the negative aspect of the projects. The committee drawn from experts from Gauhati University, Dibrugarh University,and IIT Guwahati; said in its report the main areas of concern of the LSHEP were ; low foundation of depth ( 9 meter), located on Siwalik Rock Formation and in seismically active zone between the Foot Hill Thrust ( FHT) and Main Boundary Thrust (MBT). The group also pointed out flaws in the dam design (spillway, reservoir capacity), dam break assessment for flood inundation mapping in case of failure of Gravity Dam, disturbances to aquatic flora & fauna including the river dolphin, effect on the riparian culture and the possibility of depletion of ground water etc. All these are valid points and except for the parameters of foundation depth and design of the dam, the rest are common risk associated with such projects in any seismically active and natural hotspots of the world. The Expert Group has suggested to the NHPC who has been constructed the project, the 31 recommendations to avoid downstream impact and to restore biodiversity and the ecology of the region. In general, all big dams of the world are located in such type more or less similar conditions. Hence, it is always a challenge to tackle these problems and in this case all the relevant organizations like IIT Rurkee, North East Space Application Centre, Central Ground Water Board, Central Water Commission, ONGCL ,Water Resource Department's of Assam & Arunachal, Mines & Minerals, Forest & Environemnts, Brahmaputra Board, soil & Agricultural Departments should make relevant integrated and cumulative studies. This study should not be limited to Subansiri river only but should also cover other significant river basins such as Tsangpo (Siang / Dehang in India), Sikang Debang),Luhit, Jiabharali, Kopili, Manas, Barak etc.
The NHPC has replied in a workshop held at Bibekanada Centre Guwahati on 8th October,2010 that the depth of foundation has been reduced from 16 meter (m) to 9 m as because of height of the Dam is reduced proportionally from 225 m to 116m above mean sea level. From the seismic point of view Prof, D.K.Paul,IIT Rurkee stated that the project site may contain the value of Peak Ground Acceleration ( PGA) not more than 0.33 g for all possible focus depth and moment & surface magnitude of earthquake. But the Dam is being designed considering the PGA value of 0.38 g as approved by National Committee for Seismic Design. From the seismo-tectonic data Prof. Paul stated that the detachment surface ( basement/ earthquake source) is located at a depth of 6.5 km and distance between the HFT & MBT are meeting basement surface is about 25 km which can produce moment magnitude of about 0.32 g.
However, it is not a wise option to oppose the few favorable Mega Dams rigidly, though the Northeast is seismically active region. This is also true that many of the mega dams are operating in the high seismic active zones like Mexico, Michigan, California, Arizona, Japan, Sichuan Province of China, lesser & high Himalaya of India & Pakistan. This LSHEP site is 243 km away from the epicenter of the Great Assam earthquake of 1950. It may also be mentioned that the distance between the epicenter of 1950 quake and the Sichuan earthquake of 2008, both located in the tectonic plates of India & Eurasia forming a convergent boundary, is 550 km. The time of the two earthquakes is also interesting from the point of view of earthquake return period though both the earthquakes' origin is the nature of plate and intra tectonic plates. It is also important to remember that we need multipurpose water resources projects which can provide flood cushion during peak monsoon period, irrigation facility in the pre & post monsoon season, drinking water facility, navigation system, recreational activities besides provision for geo-tourism spots. The project can also provide water flow to marshy and wetlands to maintain ecological balance and livelihood by spilling water or by transferring of river basins. These options are also feasible to maintain the ecological balance post the completion of LSHEP. Though it is true that big dam can affect the ground water table by depleting the aquifer zone but that is unlikely to happen more in LSHEP's case. Assam has good ground water resources as it falls within sub tropical climatic zone which gives maximum precipitation besides having a favourable rock formation which is good for ground water movements. In the three districts to be affected by the LSHEP, the ground water volume in Dhemaji (1023.65 million cubic meter), Lakhimpur (707.80 mcm) and Sonitpur (1023.65 mcm) is very high. The point to remember is that water is a renewable resources and its proper exploitation is necessary for mankind as well as for development of the region. Harnessing a renewable resource like water is very useful as it can help in uplifting the socio-economic status of the people by generating various employment schemes through involvement of community participation processes. The Brahmaputra and Barak basins are very rich in water resources and Northeast India which forms 8% of the country's spatial dimension is endowed with 33% of the country's water resources. But 35% of the water in the Brahmaputra comes through Tsangpo (Siang) in the Tibetan Plateau of China. All total 50.52 % of the catchments area of the Brahmaputra basin falls in the part of Tibetan China. This as we all know is uncertain strategic water for the country more so with the knowledge that China is planning to divert the Tsangpo to her own northwest territory by setting up a series of mega dams and has already started a small Run of River project (Zangmu Hydropower Station) on the river for facilitating the electricity to the construction Company. Eventually this will lead to the completion of series of mega dams for her own development putting aside the interest of global and transboundary countries. China is quite advanced in water borne technology and made the world's largest Dam, Three Gorges. Moreover, China always plays a negative policy to wards India's growth & economy and development in the international arena as India is growing as a superpower country in the forthcoming days.
Coming to the LSHEP, the Expert Group has recommended that around 450 cumec of water volume be released from the Subansiri River for survival of the aquatic flora and fauna including the river dolphin. The mean natural flow of Subansiri River during the four months periods of pre monsoon, monsoon and post monsoon is 1360 cumec, 6570 cumec and 2994 cumec respectively. Again the minimum and maximum discharge of the river is 180 cumec and 12000 cumec respectively except 21230 cumec on 11th july 1971, Whereas total capacity of discharge of LSHEP is 14603.2 cumec by spilling and head race tunnels. Of course, concept of maximum discharge is a theoretical one and may repeats after hundreds and hundreds of year. The problem of LSHEP will face is during the lean period for a few hours till the reservoir received inflow for running at least one turbine for a whole day for releasing 320 cumec as recommended by the Expert Group.Though the project is purely a run-of river project but it has a capacity to retain 441.6 MCM of water tentatively, it can retain a 5111 cumec of flood water for a day.
Perennial flood is a serious problem for Assam due to global warming, river morphology, landscape pattern and its hydrodynamic conditions. The timing and intensity of the floods is also changing continuously. Though, flood in Assam is not dependent on rainfall distribution in the Assam but it dependent on its distribution of rainfall in adjacent states in a decreasing order such as Arunachal, Meghalaya, Mizoram and Nagalnd. In 2010, rainfall intensity was normal throughout the year but abnormal rainfall was noticed in the pre-monsoon period (30% more than average) while it was minus 6% during monsoon, yet it had affected 3630 villages in 21 districts and a population of about 25 lakhs. More than 50 breaches had occurred and nearly 1.88 hectares of crop land damaged and more than 7 lakhs people had to be sheltered in relief camps. These damages to public property and infrastructure, human live , huge land erosion , huge economic losses could have been minimized if there had been a favorable water resources development projects and policies to the significant rivers in place.
The Case of the heritage Majuli Island can be cited here. A numbers of Structural mitigation measures taken up by the Ministry of Water Resources, Government of India and Government of Assam have been able to control the rate of erosion, though slowly since the year 2000. The biggest river island in the world was under severe threat from the north bank of Brahmaputra and the South east bank of Subansiri and its various tributaries coming down from the foothills of the Arunachal Himalayas. After the completion of Matmara dykes fabricated by the Geo-tube technique along with the implementation of various water resources developments project, it is expected that main Majuli Island can be preserved. However, huge amount of money will be required to take up such type of works in different areas which are being continuously eroded. The Government though has been expending thousand of crores of rupees only for the structural mitigation which is basically a short term measure. Hence, the only alternative solution is the creation of a flood water storage reservoir and a structure for flood mitigation as a long term measure.
At the same time an efficient disaster management system is also required in this region keeping view in occurrences of hydro-meteorological, geological and man made disasters. The Government of Assam is adopting various high-tech warning methodologies like the Satellite based Flood Level Early warning System (upto village level), GPRS based National Database for Emergency Management through PDS device, US-INDIA based Incident Command System (Indian Respond System) for better and an efficient preparedness. A Doppler radar will also be installed in the North-east within a short time which will give an estimate of the precipitation which will in turn help in the formation of an efficient flood regulation plan in a real time. Moreover, various structural mitigation like porcupines, geo-textiles tubes, dykes, embankment, check- dams etc and non-structural mitigation measures like building byelaws, seminar/workshops, various flood and seismic disaster management plan for the state as well as every element of social infrastructure are seriously being taken into consideration by the Government of Assam as a means of disaster risk reduction.
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