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Systematic operation of Sardar Sarovar dam 'helped avert' severe flood in Bharuch

By KV Sanghavi, JB Patel, Dr VM Yagnik, LS Sharma*

Narmada is the fifth largest river in the country and is the largest west flowing river. It also represents a classic example of integrated river basin planning and development, implemented successfully. Sardar Sarovar being the last terminal dam on this mighty river, has to face a typical tail end syndrome in terms of water management, as it has to absorb and adjust with the releases from the upstream major dams like Omkareshwar and Indira Sagar.
Almost 97% catchment of the Sardar Sarovar Project (SSP) lies in the state of Madhya Pradesh. Entire stretch of river Narmada from Amarkantak to Sardar Sarovar Project (1,163 km) was subjected to heavy rains during last one fortnight. Analysis of rainfall in Narmada basin was showing 7.4% deficit on August 16, 2020, and having 18.6% excess rainfall as on August 31, 2020.
Huge amount of water volume was received at Indira Sagar project (the largest dam in the basin), between August 20 and September 1, 2020 -- 14,660 million cubic metre of water as against the live storage capacity of Indira Sagar Project (ISP) of 9,745 million cubic metre, more than 80% of which was already filled at the beginning of this spell.
Major dams in the upstream of ISP, namely Bargi and Tawa, were also almost filled up and were not in a position to hold any more water. Consequently, Indira Sagar project continuously received more than 10 to 12 lakh cusecs of inflow, with the maximum inflow of 16.13 lakh cusecs on August 30, 2020 at 06.00 hours.
With ISP also filled up to more than 95% of its capacity, they had no other choice but to release it in the downstream. Same was the case at Omkareshwar which resulted into heavy outflow from Omkareshwar Sagar Project (OSP) and it got further added up due to heavy rains in the intermittent catchment between OSP and SSP. Compound effect of all these resulted into continuous huge inflow into SSP. 
Making use of the state of the art technology and with scientific analysis and coordinated operations of various reservoirs with the help of the Central Water Commission (CWC) and the Narmada Control Authority (NCA), the Sardar Sarovar reservoir was operated in such a way that the spillway discharge could be restricted to less than 10 lakh cusecs for most of the times with a maximum of (peak) to 10.72 lakh cusecs at 14.00 hours on September 1, 2020 (as against the spillway discharge carrying capacity of 30 lakh cusecs). 
Keeping in view the safety of the people in Bharuch city and about 30 villages on the banks of Narmada, spillway discharge was gradually managed, starting from 50,000 cusecs on August 28, 2020 at 18.00 hours to 2.65 lakh cusecs at 23.00 hours and further to 7.6 lakh cusecs at 22.00 hours on August 29, 2020. Every time advance alerts were issued to all the concerned authorities and in turn to the general public.
It is needless to state that flood routing using the available live storage capacity of the dam and keeping adequate cushion to accommodate future storms' run-off expected as per the stochastic hydrological analysis, are nothing but sound engineering principles and practices for operating spillway gates of any major dam.
Putting this into practice efficiently this year, Sardar Sarovar Dam has saved around 30,000 hectares of downstream area from the adverse hit of flood damages. This would be further evident from the fact that on August 28, 2020 at 8 am, the Sardar Sarovar Dam was already filled up 130.85 metre and was having live storage of 3,417 million cubic metre. This means that considering its live storage capacity of 5,760 million cubic metre its balance holding capacity was only 2,343 million cubic metres on that day.
Some well-known anti-dam activists have been attempting to curse Sardar Sarovar Dam and its project authorities by making false allegations
After that during August 28, 2020 to September 3, 2020, more than 10,000 million cubic metres of inflow was received at the Sardar Sarovar Dam which has been safely negotiated through scientifically carried out flood routing and that too without compromising with future flood absorption potential required to be kept on any given date.
Status of all major dams in Narmada basin as on Sepmtember 3, 2020 is as under:  
Some well-known activists who are anti-dam in general and anti-Sardar Sarovar in particular have been still attempting to curse Sardar Sarovar Dam and its project authorities by making false allegations of having created "avoidable flood disaster" (see  "Behind 'avoidable' flood disaster in Narmada from Aug 29 to Sept 1 in South Gujarat", Counterview, September 3, 2020).
Instead of allowing the people in the downstream areas to share their experience of having a great sigh of relief this year amidst very heavy rainfall in the Narmada basin, factually incorrect information is being deliberately disseminated. 
A few classic examples are: 
  1. Till Saturday, August 29, 2020 early hours, they (Sardar Sarovar Dam operators) were not releasing any water from spillway gates of dam (in fact, spillway gate operation was already started at 18.00 hours on August 28, 2020).
  2. In the evening of Tuesday September 1, 2020, they (Sardar Sarovar Dam operators) closed most of the spillway gates, thus reducing releases from spillway to less than a 10th of the earlier figure (in fact, maximum outflow from the Sardar Sarovar Dam was 10.72 lakh cusecs on September 1, 2020 at 14.00 hours which was reduced thereafter to meet with the challenges of full moon [Poonam] on September 2, 2020). 
  3. Sardar Sarovar powerhouses produced peak of 26.91 million units on September 2, 2020, this again shows underutilisation of power station (in fact, operation of the River Bed Power House was started on August 26, 2020 and gradually stepped up to operation of all the six turbines at 10.00 hours on August 30, 2020). 
  4. CWC also provided warning and advisories that Sardar Sarovar Project authorities clearly ignored (in fact, not a single warning or advisory has been ignored. on the contrary the Sardar Sarovar Narmada Nigam Limited has worked in close coordination with CWC, NCA and the authorities of upstream dams in Madhya Pradesh). 
Anyway, good part of even such misinformation campaign is that, staunch opponents of Sardar Sarovar Dam have also started believing that it has the potential to be flood moderator!
---
*KV Sanghavi is retired secretary, Government of Gujarat; JB Patel and Dr VM Yagnik are retired chief engineers, Government of Gujarat; LS Sharma is retired Managing Director, Electronics & Quality Development Centre, Government of India

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