Subansiri Basin Study – Another Chapter of Environment Subversion in Northeast

The Study The study has been done by IRG Systems South Asia Private Limited (, a subsidiary of US based IRG Systems) and[i]. It is supposed to be a Cumulative Impact Assessment of 19 HEPs planned in the basin, out of which PFRs of 7 are available, DPR of two, and one of which, the 2000 MW Subansiri Lower HEP is under construction.

Subversion of Environment Governance in the Subansiri basin While looking at this basin study, the subversion of environment governance in Subansiri basin this very millennia should be kept in mind. A glimpse of it is provided in Annexure 1. In fact, one of the key conditions of environmental clearance to the 2000 MW Lower Subansiri HEP was that no more projects will be taken up in the basin upstream of the Lower Subansiri HEP, which essentially would mean no more projects in the basin, since LSHEP is close to the confluence of the Subansiri River with Brahmaputra River. That condition was also part of the Supreme Court order in 2004. The need for a carrying capacity study was also stressed in the National Board of Wild Life discussions. We still do not have one. In a sense, the Subansiri basin is seeing the consequences of that subversion.

Map of Subansiri RIver Basin  Source:

Map of Subansiri RIver Basin

Information in public domain not known to consultants The report does not even state that Middle Subansiri dam have also been recommended TOR in 41st EAC meeting in Sept 2010. This project will require 3180 ha of land, including 1333 Ha forest land, and 2867 ha area under submergence. Even about Upper Subansiri, the consultants do not know the area of forest land required (2170 ha). So the consultants have not used even the information available in public domain in EAC meetings.

Study based on flawed and incomplete Lohit Basin Study The Study claims that it is based on Lohit Basin Study done by WAPCOS. Lohit Basin Study is an extremely flawed attempt and does not assess cumulative impacts of the cascade projects. Civil society has written about this to the EAC and the EAC itself has considered the study twice (53rd and 65th EAC Meetings), and has not accepted the study, but has raised several doubts. Any study based on a flawed model like Lohit Basin Study should not be acceptable.

A house in the upstream of Subansiri River  Source:

A house in the upstream of Subansiri River

No mention of Social impacts Major limitation of the study has been absolutely no discussion on the severe social impacts due to cumulative forest felling, flux of population, submergence, livelihoods like riparian farming and fishing, etc. Though this has been pointed out by the TAC in its meeting and field visit, the report does not reflect this.

Some key Impacts Some of the impacts highlighted by the study based on incomplete information about HEPs are:

Þ    The length of the river Subansiri is 375 km up to its outfall in the Brahamaputra River. Approximately 212.51 km total length of Subansiri will be affected due to only 8 of the proposed 19 HEPs in Subansiri River basin.

Þ    Total area brought under submergence for dam and other project requirements is approx. 10, 032 ha of eight proposed HEPs. The extent of loss of forest in rest of the 9 projects is not available.

Þ    62 species belonging to Mammals (out of 105 reported species), 50 Aves (out of 175 reported species) and 2 amphibians (out of 6 reported species) in Subansiri Basin are listed in Schedules of Wildlife Protection Act, 1972 (as amended till date).

Þ    99 species belonging to Mammals (out of 105 reported species), 57 species belonging to Aves (out of 175 reported species), 1 Reptilian (out of 19 reported species), 2 Amphibians (out of 6 reported species), 28 fishes (out of 32 reported species), 25 species belonging to Odonata of Insecta fauna group (out of 28 reported species) are reported to be assessed as per IUCN’s threatened categories.

Even this incomplete and partial list of impacts should give an idea of the massive impacts that are in store for the basin.

Cumulative impacts NOT ASSESSED Specifically, some of the cumulative impacts that the report has not assessed at all or not adequately include:

1. Cumulative impact of blasting of so many tunnels on various aspects as also blasting for other project components.

2. Cumulative impact of mining of various materials required for the projects (sand, boulders, coarse and fine granules, etc.)

3. Cumulative impact of muck dumping into rivers (the normal practice of project developers) and also of also muck dumping done properly, if at all.

Subansiri River in the Upper Reaches  Source: Lovely Arunachal

Subansiri River in the Upper Reaches
Source: Lovely Arunachal

4. Changes in sedimentation at various points within project, at various points within a day, season, year, over the years and cumulatively across the basin and impacts thereof.

5. Cumulative impact on aquatic and terrestrial flora and fauna across the basin due to all the proposed projects.

6. Cumulative impact of the projects on disaster potential in the river basin, due to construction and also operation at various stages, say on landslides, flash floods, etc.

7. Cumulative dam safety issue due to cascade of projects.

8. Cumulative change in flood characteristics of the river due to so many projects.

9. Cumulative impacts due to peaking power generation due to so many projects.

10. Cumulative sociological impact of so many projects on local communities and society.

11. Cumulative impact on hydrological flows, at various points within project, at various points within a day, season, year, over the years and cumulatively across the basin and impacts thereof. This will include impacts on various hydrological elements including springs, tributaries, groundwater aquifers, etc. This will include accessing documents to see what the situation BEFORE project and would be after. The report has failed to do ALL THIS.

12. Impact of silt laden water into the river channel downstream from the dam, and how this gets accumulated across the non-monsoon months and what happens to it. This again needs to be assessed singly and cumulatively for all projects.

13. Impact of release of silt free water into the river downstream from the power house and impact thereof on the geo morphology, erosion, stability of structures etc, singly and cumulatively.

14. Impact on Green House Gas emissions, project wise and cumulatively. No attempt is made for this.

15. Impact of differential water flow downstream from power house in non-monsoon months, with sudden release of heavy flows during peaking/ power generation hours and no releases during other times.

16. Cumulative impact of all the project components (dam, tunnels, blasting, power house, muck dumping, mining, road building, township building, deforestation, transmission lines, etc.,) for a project and then adding for various projects. Same should also be done for the periods during construction, operation and decommissioning phases of the projects.

17. Cumulative impact of deforestation due to various projects.

18. Cumulative impact of non compliance of the environment norms, laws, Environment clearance and forest clearance conditions and environment management plans. Such an assessment should also have analysed the quality of EIA report done for the Subansiri Lower hydropower project.

Wrong, misleading statements in Report There are a very large number of wrong and misleading statements in the report. Below we have given some, along with comment on each of them, this list is only for illustrative purposes.

Sr No

Statement in CIA


1 “During the monsoon period there will be significant discharge in Brahmaputra River. The peaking discharge of these hydroelectric projects which are quite less in comparison to Brahmaputra discharge will hardly have any impact on Brahmaputra.” This is a misleading statement. It also needs to be assessed what will be the impact on specific stretches of Subansiri river. Secondly, the projects are not likely to operate in peaking mode in monsoon.
2 “However, some impact in form of flow regulation can be expected during the non-monsoon peaking from these projects.” This is not correct statement as the impact of non-monsoon peaking is likely to be of many different kinds, besides “flow regulation” as the document describes.
3 “Further, during the non-monsoon period the peaking discharge release of the projects in upper reaches of Subansiri basin will be utilized by the project at lower reaches of the basin and net peaking discharge from the lower most project of the basin in general will be the governing one for any impact study.” This is again wrong. What about the impact of such peaking on rivers between the projects?
4 “The construction of the proposed cascade development of HEPs in Subansiri basin will reduce water flow, especially during dry months, in the intervening stretch between the Head Race Tunnel (HRT) site and the discharge point of Tail Race Tunnel (TRT).” This statement seems to indicate that the consultants have poor knowledge or understanding of the functioning of the hydropower projects. HRT is not one location, it is a length. So it does not make sense to say “between HRT and the discharge point of TRT”.
5 “For mature fish, upstream migration would not be feasible. This is going to be the major adverse impact of the project. Therefore, provision of fish ladder can be made in the proposed dams.” This is simplistic statement without considering the height of the various dams (124 m high Nalo HEP dam, 237 m high Upper Subansiri HEP dam, 222 m high Middle Subansiri HEP dam), feasibility of fish ladders what can be optimum design, for which fish species, etc.
6 “…water release in lean season for fishes may be kept between 10-15% for migration and sustaining ecological functions except Hiya and Nyepin HEP. Therefore, it is suggested that the minimum 20% water flow in lean season may be maintained at Hiya and Nyepin HEP for fish migration.” This conclusion seems unfounded, the water release suggested is even lower than the minimum norms that EAC of MoEF follows.

Viability not assessed The report concludes: “The next steps include overall assessment of the impacts on account of hydropower development in the basin, which will be described in draft final report.”

One of the key objective of the Cumulative Impact assessment is to assess how many of the planned projects are viable considering the impacts, hydrology, geology, forests, biodiversity, carrying capacity and society. The consultants have not even applied their mind to key objective in this study. They seem to assume that all the proposed projects can and should come up and are all viable. It seems the consultant has not understood the basic objectives of CIA. The least the consultant could have said is that further projects should not be taken up for consideration till all the information is available and full and proper Cumulative impact assessment is done.

The consultants have also not looked at the need for free flowing stretches of rivers between the projects.

Section on Environmental Flows (Chapter 4 and 9): The section on Environmental flows is one of the weakest and most problematic sections of the report, despite the fact that the Executive summary talks about it as being one of the most crucial aspects.

The study does not use any globally accepted methodology for calculating eflows, but uses HEC RAS model, without any justification. The study has not been able to do even a literature review of methodologies of eflows used in India and concludes that “No information/criteria are available for India regarding requirement of minimum flow from various angles such as ecology, environment, human needs such as washing and bathing, fisheries etc.”

This is unacceptable as EAC itself has been recommending Building Block Methodology for calculating eflows which has been used (very faultily, but nonetheless) by basin studies even like Lohit, on which this study is supposedly based. EAC has also been following certain norms about E flow stipulations. CWC itself has said that minimum 20% flow is required in all seasons in all rivers. BK Chaturvedi committee has recently stipulated 50% e-flows in lean season and 30% in monsoon on daily changing basis.

The assumption of the study in its chapter on Environmental Flows that ‘most critical reach is till the time first tributary meets the river” is completely wrong. The study should concentrate at releasing optimum eflows from the barrage, without considering tributary contribution as an excuse.

First step of any robust eflows exercise is to set objectives. But the study does not even refer to this and generates huge tables for water depths, flow velocity, etc., for releases ranging from 10% lean season flow to 100% lean season flow.

After this extensive analysis without any objective setting, the study, without any justification (the justification for snow trout used is extremely flawed. Trouts migrate twice in a year and when they migrate in post monsoon months, the depth and velocity needed is much higher than the recommended 10% lean season flow) recommends “In view of the above-said modeling results, water release in lean season for fishes maybe kept between 10-15% for migration and sustaining ecological functions except Hiya and Nyepin HEP. Therefore, it is suggested that the minimum 20-25% water flow in lean season may be maintained at all HEP for fish migration and ecological balance.”

The study does not recommend any monsoon flows. Neither does it study impact of hydro peaking on downstream ecosystems.

Shockingly, the study does not even stick with this 20-25% lean season flow recommendation (20-25% of what? Average lean season flow? Three consecutive leanest months? The study does not explain this). In fact in Chapter 9 on Environmental Flows, the final recommendation is: “Therefore, it is suggested that the minimum 20-25% water flow in lean season may be maintained at Hiya and Nyepin  HEP or all other locations for fish migration.” (emphasis added)

So it is unclear if the study recommends 20-25% lean season flows or 10-15% lean season flows. This is a very flawed approach to a critical topic like eflows.

The study keeps mentioning ‘minimum flows’ nomenclature, which shows the flawed understanding of the consultants about e-flows.

The entire eflows section has to be reworked, objectives have to be set, methodology like Building Block Methodology has to be used with wide participation, including from Assam. Such exercises have been performed in the past and members of the current EAC like Dr. K.D. Joshi from CIFRI have been a part of this. In this case, EAC cannot accept flawed eflows studies like this. (DR. K D. Joshi has been a part of a study done by WWF to arrive at eflows through BBM methodology for Ganga in Allahabad during Kumbh: Environmental Flows for Kumbh 2013 at Triveni Sangam, Allahabad and has been a co author of this report)

Chocolate Mahseer in Subansiri  Source:

Chocolate Mahseer in Subansiri

Mockery of rich Subansiri Fisheries Subansiri has some of the richest riverine fisheries in India. The river has over 171 fish species, including some species new to science, and forms an important component of livelihood and nutritional security in the downstream stretches in Assam.

But the study makes a mockery of this saying that the livelihoods dependence on fisheries is negligible. The entire Chapter on Fisheries needs to be reworked to include impacts on fisheries in the downstream upto Majuli Islands in Assam at least.

No mention of National Aquatic Animal! Subansiri is one of the only tributaries of Brahmaputra with a resident population of the endangered Gangetic Dolphin, which is also the National aquatic animal of India (Baruah et al, 2012, Grave Danger for the Ganges Dolphin (Platanista ganegtica) in the Subansiri River due to large Hydroelectric Project

Shockingly, the Basin Study does not even mention Gangetic Dolphin once in the entire study, let alone making recommendations to protect this specie!

Gangetic Dolphin is important not only from the ecological perspective, but also socio cultural perspective. Many fisher folk in Assam co-fish with the Gangetic River Dolphin. These intricate socio ecological links do not find any mention in the Basin study, which is unacceptable.

Agitation Against Lower Subansiri Dam in Assam Source: SANDRP

Agitation Against Lower Subansiri Dam in Assam
Source: SANDRP

Lessons from Lower Subansiri Project not learnt A massive agitation is ongoing in Assam against the under construction 2000 MW Subansiri Lower HEP. The people had to resort to this agitation since the Lower Subansiri HEP was going ahead without studying or resolving basic downstream, flood and safety issues. The work on the project has been stopped since December 2011, for 22 months now. In the meantime several committee have been set up, several changes in the project has been accepted. However, looking at this shoddy CIA, it seems no lessons have been learnt from this ongoing episode. This study does not even acknowledge the reality of this agitation and the issues that the agitation has thrown up. There is no reflection of the issues here in this study that is agitating the people who are stood up against the Lower Subansiri HEP. The same people will also face adverse impacts of the large number of additional projects planned in the Subansiri basin. If the issues raised by these agitating people are not resolved in credible way, the events now unfolding in Assam will continue to plague the other planned projects too.

Conclusion From the above it is clear that this is far from satisfactory report. The report has not done proper cumulative assessment on most aspects. It has not even used information available in public domain on a number of projects. It does not seem to the aware of the history of the environmental mis-governance in the SubansiriBasin as narrated in brief in Annexure 1. For most projects basic information is lacking. Considering the track record of Central Water Commission functioning as lobby FOR big dams, such a study should have never been given to CWC. One of the reasons the study was assigned by the EAC to the Central Water Commission was that the CWC is supposed to have expertise in hydrological issues, and also can take care of the interstate issues. However, the study has NOT been done by CWC, but by consultants hired by CWC, so CWC seems to have no role in this except hiring consultant. So the basic purpose of giving the study to CWC by EAC has not been served. Secondly the choice of consultants done by the CWC seems to be improper. Hence we have a shoddy piece of work. This study cannot be useful as CIA and it may be better for EAC to ask MoEF for a more appropriate body to do such a study. In any case, the current study is not of acceptable quality.

South Asia Network on Dams, Rivers & People (


Set Conditions to be waived Later – The MoEF way of Environmental Governance

In 2002, the 2,000 MW Lower Subansiri hydroelectric project on the Assam-Arunachal Pradesh border came for approval to the Standing Committee of the Indian Board for Wildlife (now called the National Board for Wildlife) as a part of the Tale Valley Sanctuary in AP was getting submerged in the project. The total area to be impacted was 3,739.9 ha which also included notified reserved forests in Arunachal Pradesh and Assam.  The Standing Committee observed that important wildlife habitats and species well beyond the Tale Valley Sanctuary, both in the upstream and downstream areas, would be affected (e.g. a crucial elephant corridor, Gangetic river dolphins) and that the Environmental Impact Assessment studies were of a very poor quality. However, despite serious objections raised by non-official members including Bittu Sahgal, Editor, Sanctuary, Valmik Thapar, M.K. Ranjitsinh and the BNHS, the Ministry of Environment & Forests (MoEF) bulldozed the clearance through in a May 2003 meeting of the IBWL Standing Committee. Thus a project, which did not deserve to receive clearance, was pushed through with certain stringent conditions imposed (Neeraj Vagholikar, Sanctuary Asia, April 2009).

Lower Subansiri HEP Source: The Hindu

Lower Subansiri Dam
Source: The Hindu

The EC given to the project was challenged in Supreme Court (SC) by Dr L.M Nath, a former member of the Indian Board for Wildlife. Nath pleaded, these pristine rich and dense forests classified as tropical moist evergreen forest, are among the finest in the country. Further the surveys conducted by the Botanical Survey of India and the Zoological Survey of India were found to be extremely poor quality. The Application mentions that the Additional DG of Forests (Wildlife) was of the view that the survey reports of the BSI and ZSI reports were not acceptable to him because these organisations had merely spent five days in the field and produced a report of no significance.

The SC gave its final verdict on 19-4-2004, in which the Court upheld the EC given by MoEF to NHPC but with direction to fulfill some important conditions. Out these conditions there were two conditions which were very significant – “The Reserve Forest area that forms part of the catchment of the Lower Subansri including the reservoir should be declared as a National Park/ Sanctuary. NHPC will provide funds for the survey and demarcation of the same.”, and “There would be no construction of dam upstream of the Subansri River in future.” These conditions were also mentioned in the original EC given to the project in 2003.

In May 2005, two years after the EC was given the Arunachal Pradesh govt and NHPC approached the SC to waive or modify the above two conditions. The state government calimed that following these conditions would imply loss of opportunity to develop 16 mega dams in the upstream of Lower Subansiri (this including 1,600 MW Middle Subansiri and 2,000 MW Upper Subansiri to be developed by NHPC). The SC sent it back to National Board for Wildlife to review the conditions.

The petition was done strategically. “The strategy of the dam proponents is simple. They raised no objection to the terms until the construction of the Lower Subansiri project had proceeded beyond a point when it could have been cancelled. Armed with this fait accompli, they asked for a review of the clauses on the very basis on which the original clearance – laid down by members who were subsequently dropped from the wildlife board – was granted.”[ii]

Then nonofficial members of NBWL expressed their dissent to the proposal. In a May 2008 communication to the Chairman of the NBWL Standing Committee, member Dr. Bibhab Talukdar observed: “If the Standing Committee agrees to waive the conditions, we would be setting a dangerous precedent and sending a wrong signal regarding the credibility of decision-making by us. This would mean that projects impacting rich wildlife habitats can receive clearances based on stringent conditions, only to be up for review later. Such an approach is undesirable both from a perspective of good governance as well as the long-term interest of wildlife in the country.”

Dr. Asad Rahmani of the BNHS, who was part of a sub-committee of the NBWL Standing Committee conducting a site visit to the project area, stated in his report: “Under no circumstances should new projects be allowed in the Subansiri river basin until an advance cumulative assessment of proposed projects and a carrying capacity study of the Subansiri river basin are completed.”

In the December 12 2008 meeting of NBWL Standing Committee, even after these dissenting opinions from nonofficial members MoEF managed to do a dilution of the above two conditions. Assam that time was witnessing a major protest concerning the downstream impacts of Lower Subansiri HEP but it was not even consulted. Shockingly the “no dam upstream” condition was removed and it was decided that “any proposal in the upstream of the SubansiriRiver would be considered independently on its merit by the Standing Committee as and when submitted by the proponents”.

Now the Arunachal Pradesh government needs to declare a smaller area of 168 sq. km. as a sanctuary and “make serious efforts” to bring an additional 332 sq. km. reserved forest under the category of Conservation Reserve (CR) in consultation with the MoEF. The latter part of the condition (declaration of CR) is non-enforceable because of the choice of words. Even the demand to at least conduct an advanced cumulative impact assessment of proposed projects and a carrying capacity study of the Subansiri river basin has been ignored[iii].

As Bittu Sahgal, Editor, Sanctuary Asia says, “The Lower Subansiri is one such, where the PMO has placed a very dubious role in forcing clearances, agreeing to clearance conditions and then starting the project, only to loosen the environmental conditions. In this whole scam the Zoological Survey of India and the Botanical Survey of India have been co-conspirators that have suppressed the ecological value of the forests to facilitate the building of the dam, which will drown pristine elephant, tiger and clouded leopard forests and cause havoc downstream as well.”

The above sequence of events are very pertinent to remember as we see the Subansiri basin study.


[i] Website says: “More than 200 successful environmental Impact Assessment Clearance from Ministry of Environment & Forests, Government of India for Industry, Infrastructure & Construction projects” Sounds strange from an EIA consultant.

[iii] For more details please see – “Forest Case Update”, Issue 1, June 2004 and “The Subansiri Subversion” by Neeraj Vagholikar published in Sanctuary Asia, April 2009 issue

3 Comments on “Subansiri Basin Study – Another Chapter of Environment Subversion in Northeast


    Doubts raised over CWC study on Subansiri project
    STAFF Reporter
    GUWAHATI, Oct 11 – The consultants IRG Systems South Asia Private Limited, a subsidiary of US based IRG Systems, have not used even the information available in public domain in carrying out the ‘Basin wise environmental Impact Assessment Study on Subansiri sub basin in Arunachal Pradesh’ on behalf of the Central Water Commission (CWC). The study is based on flawed and incomplete Lohit Basin Study and has no mention of the social impacts of the projects being executed in the sub-basin.
    Above were the observations made by voluntary organization South Asia Network on Dams, Rivers and People (SANDRP) in a letter to the chairperson and members of the Expert Appraisal Committee (EAC) on River Valley and Hydroelectric Projects of the Union Ministry of Environment and Forests on the July 5, 2013 Revised Interim Report, Volume 1 of the CWC on the matter.

    Further, the voluntary organization said the consultants have not assessed the cumulative impacts of the hydroelectric projects proposed on the sub-basin.

    For example, it said the cumulative impact of blasting for tunnels as also blasting for other project components, cumulative impact of mining of various materials required for the projects like sand, boulders, coarse and fine granules etc, cumulative impact of muck dumping into the rivers etc have either not been done at all or not done adequately by the consultants.

    There are a very large number of wrong and misleading statements in the report. Citing examples of such misleading information provided by the report, the voluntary organization alleged that the claim of the consultants that during the monsoon period there will be significant discharge in Brahmaputra river and the peaking discharge of these hydroelectric projects which are quite less in comparison to Brahmaputra discharge will hardly have any impact on Brahmaputra was one such misleading information.

    Moreover, the consultants have failed to assess the viability of the projects proposed in the sub-basin area.

    Besides, the section on environmental flows in one of the weakest and most problematic sections of the report, said the voluntary organization.

    It further maintains that the entire environment flows section of the report has to be reworked.


  2. on Oct 14, 2013

    EAC on CEIA Study: Directs CWC to include major parameters of proposed HEPs for Subansiri basin study

    Oct 14: The Cumulative Environmental Impact Assessment (CEIA) of Subansiri Sub-Basin by the Central Water Commission (CWC) was discussed by the Expert Appraisal Committee for River Valley and Hydroelectric projects in its 68th meeting.
    8As per the minutes of the meeting, CWC, represented by the consultant it appointed for the Basin study, presented that 19 hydroelectric projects are envisaged in the Subansiri sub-basin with 7 pre-feasibility study reports and two DPRs available of the 19 projects.
    8While CWC’s consultant apprised that 10,032 ha of land will be brought under submergence due to nine proposed HEPs, the extent of loss of forest in the rest of the other projects are not available.
    8Considering the information presented by the consultant, the EAC discussed the matter in detail and advised the consultants to provide the report on downstream impact study and also suggested that micro HEPs be included in the study for a more holistic and integrated examination.
    8Directing the consultant to upload the draft report in the web portal for gathering comments and opinions from the general public, the EAC also directed to include major parameters of proposed projects in the final report. The report may also recommend dropping certain projects if necessary for the overall interest of the environment, added EAC.


  3. Pingback: Experts call for major redesign of India’s largest dam | The Third Pole

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