Severity of Assam floods heightens old fears about dams in the Brahmaputra basin

After the Ranganadi – a tributary of the Brahmaputra – overflowed and submerged large swathes of land in Assam’s Lakhimpur district on July 9, calls to decommission the dam on the river have grown loud again. The dam, people in Lakhimpur claimed, exacerbated the floods worse than ever this year.

The Assamese press has also heavily criticised the North Eastern Electric Power Corporation Limited, the public-sector company that administers the dam.

Old accusation, new occasion

The accusation that the Ranganadi dam aggravates the problem of flooding in the downstream district of Lakhimpur is as old as the dam itself, which became operational in 2001.

The Ranganadi dam was touted as the North East’s first run-of-the-river dam. These dams differ from conventional dams as they do not have huge reservoirs but generate electricity by harnessing the energy of flowing water. The dam is located at Yazali in Arunachal Pradesh’s Lower Subansiri district. As water from the Ranganadi flows downstream from Arunachal Pradesh to enter Lakhimpur in Assam, the dam’s walls stop the flow. Then, a certain amount of the water is chanelled into a tunnel over a distance of 10 km. The tunnel drops 600 metres to another river called Dikrong. This is done so as to achieve the head – the difference in height – required for the water to rotate turbines that produce electricity.

Dikrong is one of the bigger north bank tributaries of the Brahmaputra. It originates in the Nyishi hills of Arunachal Pradesh, flows through the state’s capital Itanagar, before flowing downstream to the plains of Assam where it joins the Subansiri-Brahmaputra river system at Lakhimpur.

Environmentalists have contested the Ranganadi dam’s claim to run-of-the-river status, pointing out that the transfer of its waters through the artificial channel from Ranganadi to Dikrong has dried up the Ranganadi.

Besides, people living in the areas downstream say that the river bed has become shallow over the years as silt from the dam site at Yazali is periodically flushed into the Ranganadi river. While the exercise is imperative to keep the dam in good health, residents of Lakhimpur believe it has increased the frequency and intensity of flash floods in the district.

The North Eastern Electric Power Corporation Limited has consistently denied these allegations, which crop up every time there is a particularly harsh wave of floods in the district.

This year too, as news spread about the alleged role of the dam in the current wave of floods in Lakhimpur that has killed at least 11 people, the company said that the dam had, in fact, minimised damages. In a press-release, the company blamed the floods on the “incessant torrential rainfall in the catchment areas of river Ranganadi since June 30”.

Damage control

But with Assam’s civil society organisations refusing to buy that defence and threatening a mass agitation, the public sector organisation held a press conference at its headquarters in Shillong, where its chairman and managing director AG West Kharkongor addressed the media on July 18.

“There has been a lot of misinformation that the havoc that has been caused in the district has been attributed to the release of water by NEEPCO [North Eastern Electric Power Corporation],” Kharkongor reportedly said. He then went on to explain how the dam helped cushion the impact of the July 9 floods by diverting a portion of the Ranganadi’s water into the Dikrong.

Kharkongor was referring to the water that goes into producing electricity. As the Ranganadi is stopped by the walls of the dam, 160 cubic metres per second of its water is channeled into a tunnel. The water finally strikes three turbines with force, generating electricity. The chairman further added that inflow of water on July 9 had reached over 1,500 cubic metres per second, and since the capacity of Ranganadi’s reservoir was only 200 cubic metres per second, there was no choice but to release the excess water to protect the structure.

‘Abnormal and unusually fast’

However, Kharkongar’s first claim that the dam controlled the flood damage on July 9 was contradicted by the Ranganadi project’s senior manager, S Sharma.

Sharma told Scroll.in that the tunnel that transferred water from Ranganadi to Dikrong had “stopped working for some time” that day as the generator that drove the water in the tunnel malfunctioned, resulting in the water being released back into the Ranganadi. “It was a mechanical fault,” he said. “You cannot anticipate such things.” However, Sharma maintained that 160 cubic metres per second of water was a trivial quantity, and would have not have significantly added to the deluge. “It would have happened anyway,” he insisted.

According to Arup Kumar Sarma, professor of civil engineering at the Indian Institute of Technology in Guwahati, the significance of an extra 160 cubic metres per second of water was subjective. “It really depends on how much water Ranganadi could hold that day in the areas it overflowed,” he explained.

The capacity of the river is 1,291 cubic metres per second. People in Lakhimpur, thus, believe that a difference of 160 cubic metres per second may have made a difference. “We understand that they have to release water, and we have made peace with that,” said Dwarika Prasad, a resident of Gourighat Balijan village, one of the worst-affected places in the floods. “But since they have made the river bed shallow, even if a small amount is diverted it is a big respite [for people in downstream areas].”

A river that changes every season

By design, if the Ranganadi flow is greater than 160 cubic metres per second, the surplus water is released into the river downstream to protect the dam. In the winter, the river flow is, more often than not, less than that. Therefore, no water is released into the Ranganadi at all, which results in a practically dead river. “We can cross the river on foot in the winter,” several people living in downstream areas in Lakhimpur district said.

In the summer, however, as torrential showers strike the region, the river flow invariably exceeds 160 cubic metres per second. This leads to the release of water from the dam. The North Eastern Electric Power Corporation Limited argues that the water is the Ranganadi’s itself, so the dam could not possibly be held responsible for the floods.

The different natures of flooding

That is a contention that environmentalists and people living in downstream areas strongly disagree with. “This is not about the volume of the water,” claimed Partha Jyoti Das, head of the Water, Climate and Hazards Programme of the Guwahati-based non-profit Aaranyak. “The nature and patterns of the floods would have been very different in the absence of the dam. People living in downstream areas always lived with natural floods always, but with the dam, the river’s course has been altered and the nature of floods has completely changed. Yes, there would be floods even without the dam, but the hazards would be much less.”

Residents of the many downstream villages Scroll.in visited agreed, saying that the force of the water has become much greater ever since the dam came into existence. “You should see the way the water came this time,” said Dipen Bora of Amtala village, which was ravaged by the floods on July 9. “It did not seem like river water, it was like water in a drain.”

Also, people claim that the continuous flushing of sediments at the dam site at Yazali has raised the river bed significantly, so it was unfair to say that the dam has not increased the intensity of the floods.

National security vs research

However, Das, who is currently working on a report on the Ranganadi, conceded that in the absence of scientific data it was difficult to counter the North Eastern Electric Power Corporation Limited’s claims. “The government just won’t release data to researchers, citing national security issues,” claimed Das, co-author of Damming Northeast India, a study of hydropower development in the region. “That is why NEEPCO gets away always.”

He added: “The last time there was a huge flood in 2008, IIT Guwahati was supposed to come out with a fact-finding report. The report hasn’t been made public till date.”

Other academics who have tried studying the Ranganadi also bemoaned the lack of transparency. “They can never be wrong technically, because they provide no information to prove them otherwise anyway,” said a researcher who had studied flood forecasting systems in context of the river, who did not want to be identified. “It is like being asked to validate black holes without a telescope or scientific equipment.”

In India, flow data of the rivers in the Indo-Gangetic and Brahmaputra basins is treated as classified and covered under the Official Secrets Act. This has often hampered research. For instance, in 2010, a government glaciologist VK Raina was refused access to his own work that he had done during his tenure in the Geological Survey of India, on the grounds of secrecy.

Of warnings

In Lakhimpur, however, people want something much simpler: an early warning system that informs them of the incoming water from the dam. “Earlier we’d see the river, and know what to expect and prepare accordingly,” said Keramat Ali, a resident of Bogoleejaan village near North Lakhimpur town, where the river wreaked havoc earlier this month. “But now with the dam, it all depends on when they release water. And now the water comes in much faster than earlier, so we have no time to react, and, say, take our cows to higher grounds at least, if nothing else.”

Although a siren goes off 30 minutes at the site of the dam before water is released, people living in downstream areas of Lakhimpur, which is almost 100 km from the dam, are too far to hear it. Additionally, the dam authorities inform Lakhimpur’s district administration, which is supposed to make public announcements.

According to people living in downstream areas of the district, the district administrator has often failed to warn people. Public announcements are rare. Even if they are made, it is only in and around the town or North Lakhimpur, said residents of villages along the river in Lakhimpur. “I’ve never heard any kind of public announcement, informing us of water being released,” said Bhadreshar Baruah of Amtala village.

Lakhimpur deputy commissioner Barun Bhuyan claimed information was erratic and often not relayed on time. “NEEPCO [North Eastern Electric Power Corporation] should also make public announcements in the downstream villages, but they do not,” he said. “After all, it is their dam.”

In 2015, the North East Electrical Power Corporation pledged to sponsor a community-based flood early warning system on the downstream of Ranganadi river in Lakhimpur. However, no such system exists, an official from the district administration claimed.

Professor Sarma of IIT-Guwahati said that since the water stopped by the gates of the dam came down with considerable force when released, it was important to have a series of alarms. “One alarm won’t work because of the distance, so there could be a series of alarms, each at a fixed distance from the previous [one],” he said. “It is called a relay alarm system, each alarm triggering off the next.”

The big dam looming

As Lakhimpur recovers from one of its worst floods in almost a decade, residents are keeping their fingers crossed. Even as they get used to the Ranganadi dam, they may have to confront a much bigger dam soon: the 2,000-megawatt Lower Subansiri hydropower project on the Subansiri river. (The Ranganadi dam’s power-generation capacity is 405 megawatts – almost one-fifth of the Lower Subansiri.)

The Subansiri is another tributary to the Brahmaputra, albeit much bigger than the Ranganadi. Construction of the dam has been kept on hold since 2011 following an order of the National Green Tribunal and mass protests by various indigenous groups.

But recently, the Assam Assembly’s voiced unanimous support for the project and the chief ministers of Assam and Arunachal Pradesh promised to fast-track it, so construction may resume soon.

In the wake of the floods, fears about the Lower Subanisiri project have increased even more among residents in Lakhimpur. “The Ranganadi, they say, is a small dam,” said a farmer in Bogoleejaan. “If a small dam can cause so much damage, I don’t know how much a big dam will.”

“Well, if they build that dam, our Lakhimpur will become a rich place,” remarked another resident of North Lakhimpur town. “After all, only the rich can afford to stay in water-proof houses on five-metre high platforms, isn’t it?”

This is the second of a two-part series on the floods in Assam. Read the first part here.