When Dhansiri river broke the highest flood level mark at Numaligarh site in early hours of Aug 2, 2018 in Golaghat district in Assam, it was not only completely out of the blue, the whole episode was unprecedented.
The earlier Highest Flood Level of Dhansiri River at Numaligarh was 79.87 m. The new HFL, it seems, was 80.18 m, full 31 cm above the previous HFL. This is rather rare, normally the new HFL would be a few cm higher, not almost one third of a meter. Secondly, the water level remained above 79.87 cm, the old HFL, for over 60 hours. This is also unusual, normally the water level rarely remains above HFL for more than a day or so. Thirdly, the earlier HFL was achieved on Sept 24, 1985, so this sudden episode of flood was breaking 33 year old record.
But more surprising was that when we go through the IMD’s daily district level rainfall, we find that there has not been unprecedented rainfall in the Dhansiri River Catchment in the week preceding Aug 2, 2018, though there was some rainfall, the catchment has in fact seen deficit rainfall this monsoon. Similarly, there were no signs of such unprecedented rainfall or flood levels in other rivers around Dhansiri.
So what brought the unprecedented floods in Dhansiri River? The Assam Chief Minister, and groups like AASU and KMSS provide a clue when they allege that the Doyang Hydropower Dam upstream in Wokha district in Nagaland played a role. Did it?
Particularly when NEEPCO, the central govt company that owns and operates the dam claimed, on the contrary that Doyang dam helped moderate the flood peak in downstream river. But every dam operator makes such claims. Theoretically, every dam can help moderate flood in the downstream river, provided it is operated to achieve that objective. Most dams do not.
What are the facts about Doyang? Doyang dam has gross storage capacity of 535 Million Cubic Meters (MCM) and live storage capacity of 370 or 400 MCM as per different sources, NEEPCO website does not provide even these figures.This is substantial storage. The spillway of the dam has a capacity to release 5977 cumecs of water. This is massive, massive quantity for Doyang-Dhansiri rivers. So the dam certainly has the capacity to bring massive flood disaster in the downstream area if it is not operated properly.
So how was the dam operated? Shockingly, NEEPCO’s website provide no information about how the dam was operated in days preceding the Aug 2-4 Golaghat floods. NEECO website also does not provide any information as to how the dam is supposed to operate, particularly during monsoon.
We find a clue about this from a CERC (Central Electricity Regulatory Authority, a statutory body) order, which provides the month wise design power generation figures for the Doyang Project. It says the Doyang project is supposed to generate 14.28 Million Units (MU) of electricity in whole of July.
How much electricity did Doyang produce in July 2018? According to National Power Portal of Central Electricity Authority of Government of India, Doyang Project produced 45.52 MU in July 2018!!! That is more than three times the electricity it is supposed to produce in July. This also tells us that by design, NEEPCO is supposed to keep water level low during July 2018, so that there is minimum risk of floods to the downstream areas, but NEEPCO was completely violating that norm on daily basis. NEEPCO could not have produced three times the design energy without keeping the water level high in the dam, which is also completely against the basic principle of flood management.
And then when there was some heavy rainfall in the catchment area of Doyang project, NEEPCO claimed helplessness, saying we had no option but to open the gates to release the water. In press statement NEEPCO claimed that it had to open the dam gates on July 27, when downstream river was also flooded, creating unprecedented flood disaster in Golaghat.
But even July 27 onwards, NEEPCO continued to generate maximum electricity. So Doyang project generated, as per NPP website, 1.70 MU on July 31, 1.71 MU each on July 28-30, 1.76 MU on July 27, 1.78 MU on July 26, 1.67 MU each on July 20-24-25. This clearly means that the water level in Doyang dam even on July 24-31, was very high for NEEPCO to be able to generate so much electricity throughout this period. NEEPCO has clearly, completely violated the basic safety norms and design norms in order to generate maximum power in July 2018.
In Conclusion Some of the recommendations that flow from above analysis:
- NEEPCO must accept that Doyang dam did have a significant role in increasing the flood disaster in Dhansiri river, Golaghat district during Aug 2-4, 2018. NEECO should compensate all those who have suffered due to the floods.
- NEEPCO needs to assure everyone that it will adhere to the design norms and not increase the water level in dam to generate more power when it is not supposed to.
- NEECO must put on its website, on daily basis, what is the Doyang water level, how much was inflows and how much was the water out flow and power generation. It can be on the lines of what Narmada Control Authority does[i], see: http://nca.gov.in/dsr/dsr-aug-18/dsr-7-aug-2018.pdf.
- NEEPCO should also put up on its website the Dam Operation Manual, including the rule curve that would state how the dam is supposed to be operated in filling period.
- CWC needs to include Doyang reservoir in its inflow forecasting in its Flood Forecasting system.
- CWC, IMD and NEEPCO needs to provide the daily rainfall in catchment of Doyang Dam on daily basis. For this they will need to put up rainfall measuring and transmission system. Today, even IMD’s daily district wise rainfall bulletin has blank spaces for every single day during July 25-Aug 6 for Doyang-Dhansiri catchment districts like Phek, Peren and Zunheboto districts in Nagaland.
More details about the Dhasiri Floods in Aug 2018 and role of Doyang Dam:
One of the earlier reports[ii] said on July 31, 2018 about the floods in Golaghat district: “A total of 36 villages of Golaghat district have been reeling under flood waters due to discharge of water from the dam of the Doyang Hydroelectric Project (DHEP) located in Wokha district of Nagaland. This has triggered panic among the affected villagers in the district. The DHEP authority opened its sluice gates on Friday (July 27) to discharge excess water of the Doyang reservoir which keeps on increasing due to the incessant rains that have been continuing for the last couple of days in Wokha.”
The report quoted Rony Rajkumar, Project officer of District Disaster Management Authority of Golaghat district: ““The DHEP authority has informed us that once the water level in the Doyang reservoir comes below 324 meter, they will close the gates. They have also refuted all the rumours about the vulnerability of the dam due to the flood.” This thus officially confirmed that Doyang reservoir did have a role to play.
Reconfirming Doyang Dam’s role, the same report quoted Nina Barua, district information and public relations officer of Golaghat district saying: “As informed by the North Eastern Electric Power Corporation Limited (NEEPCO) authority due to continuous rains in the catchment area, the water level of Doyang reservoir has been on the rise. In the meantime, all the gates are open for release of excess water from the dam”.
This was also confirmed by NEEPCO statement published in the Shillong Times: “The reservoir water level started increasing abruptly since July 25, 2018 with incessant rainfall in the upper catchment area. The inflow to the reservoir increased from over 600 cum/sec to over 1150 cum/sec on July 31, 2018, which is much higher than the normal range of inflow and necessitated release of excess water in a controlled manner by opening the radial gates at 5:30 am of July 27, 2018,” the NEEPCO statement said.
The gates were closed at 5 am on Aug 5, 2018, once the water level in Doyang reservoir went below 324 m.[iii] According to DDMA authorities, the stagnant flood waters will take about a week to recede completely even if there is no more rain.
According to Daily power generation reports[iv] on National Power Portal, the Doyang project generated 1.73 MU on July 29, 2018 (1.70 MU on July 31, 1.71 MU each on July 28-30, 1.76 MU on July 27, 1.78 MU on July 26, 1.67 MU each on July 20-24-25, 1.43 on July 23, 1.54 on July 22, 1.46 each on July 9-10-21, 1.66 each on July 16-19, 1.68 on July 18, 1.65 on July 16, 1.24 on July 15, 1.57 on July 14, 1.53 on July 13, 1.47 on July 12, 1.52 on July 11, 1.41 on July 8, 1.36 each on July 1-2-6-7, 1.14 on July 5, 0.91 on July 4, 1.26 on July 3), against normal program generation of 1.35 MU. The project generated 25.08 MU during April-May 2018 and 26.99 MU during June 2018. During July 1-31, the project has generated 45.52 MU power.
Some salient features of the Doyang Project as per National Register of Large Dams[v]:
- Dam has live storage capacity of 216.5 MCM at EL 324.0 M and intercepts a catchment area of 2606 sq.km.[vi]
In the past too downstream affected people in the ten villages of Mengshanpen, Tsopo, Chudi, Longtsung, Sheruechuk, Morakjo, Lotsu, Pyangsa, Moilan and Pyotchu have said that the Doyang project led to very serious impacts in the downstream areas[vii]. The ten affected villages, under the banner of the Downstream Affected People’s Organization (DAPO), had in Aug 2015 submitted a representation to the Chairman and Managing Director of the North Eastern Electric Power Corporation Limited (NEEPCO), their grievances include:
- Death of at least five persons between 2003 and 2014 due to the sudden “release of huge volumes of water”.
- Very large number of people have suffered loss of livelihood. Movement of people across the river has been severely hampered.
- Destruction of access to river, fisheries, water sources, hanging bridges, sand and boulder sources and river bed cultivation.
[ii] https://nenow.in/north-east-news/assam-doyang-dam-waters-inundate-36-golaghat-villages.html, this was largely repeated the next day in TELEGAPH: https://www.telegraphindia.com/states/north-east/doyang-water-floods-assam-249078. There were more reports: https://northeastlivetv.org/2018/08/01/flash-floods-hit-upper-assam-after-neepco-releases-excessive-water-from-nagalands-doyang-hydro-project/, http://www.assamtribune.com/scripts/detailsnew.asp?id=aug0618/at062