Poor management of dams exacerbate floods, instead of mitigating them, it adds
There is no doubt that heavy and erratic rainfall is one of the reasons for floods in several states. But that is often coinciding with dams being full due to poor management, resulting in dam-induced floods.
With Maharashtra, Karnataka and Kerala among other states under deluge, questions are being raised over their flood management system. The disaster aggravates by the release of water from overflowing dams in the region at the same time that relentless rainfall hits it.
An assessment of the Krishna river basin by South Asia Network On Dams, Rivers and People (SANDRP) shows how mismanagement on releasing the water from various dams worsened the flood situation in Kolhapur, Sangli, and Satara districts of Maharashtra.
Three of the big dams in the region — Koyna, Radhanagari, and Warna — were almost 100 per cent full by August 5, when the current floods started.
The Radhanagri dam was close to 80 per cent full by July 25 and the Koyna and Warna dams were around 50 per cent full, according to the Central Water Commission live storage data. But no water was released from these till then.
The report says that if these dams had started releasing water from July 25, they would have had sufficient space during the first week of August when the districts received heavy rainfall and that would have helped reduce the floods. The dams, that were supposed to help moderate the flood situation, instead ended up exacerbating it.
Similarly, delaying the release of water from the Hidkal dam in Belagavi district of Karnataka had a huge influence on worsening the flood situation as operators waited for the dam to be almost full. This, despite the India Meteorological Department (IMD) giving a monsoon forecast at least five days in advance.
“Till August 5, the release was a paltry 2,400 cusecs. As soon as the dam was full, the water releases went up to 29,429 cusecs on August 6, which then kept climbing up to 100,945 cusecs on August 9. Then, excess release started on August 6, coinciding with the flood peak,” the report stated.
Experts say that due to uncertainty in rainfall and fear of dry conditions in future, dam operators think of storing as soon as water is available but that proves costly during flood fury as then there is no alternative but to release all the inflow downstream.
Shripad Dharmadhikary, founder of non-profit Manthan Adhyayan Kendra, said the management of operations of reservoirs was missing completely due to the lack of coordination both at reservoir level as well as the basin level.
“For example, at the beginning of the monsoon, reservoirs in Maharashtra and Karnataka were filled up. But the people responsible for operations work in silos and do not work with the IMD to understand the pattern of rainfall," he said.
"Hence, they thought of maximising the levels, thinking about the uncertainty of rain during the later monsoon. There is no accountability of the officials in charge of maintaining the reservoirs and hence they fail to communicate with IMD. There should be a clear-cut protocol for maintaining the reservoir levels,” he added.
However, the government has still not acknowledged the problem as no lessons were learnt after the Kerala floods of 2018 when dams violated the rule curve, which tells how the dam is supposed to be filled during the monsoon to optimise flood moderation for the downstream area.
AK Gosain from the Indian Institute of Technology, Delhi, said if the amount of water flowing to the reservoir was known beforehand, the water level in the reservoir could be managed. This could be done through the simulation models which depend on the size of the catchment.
“For example, we can evacuate the extra amount coming to the reservoirs and at the end of the event, can still capture the desired amount from the rivers,” he said, adding that even real time flood monitoring and methodologies calculating the flow of the river, which could effectively help in management of dam levels under variable rainfall patterns, were available in the country but were rarely used.
Resilient to climate change?
In an era of extreme climate episodes, another question that needs to be asked is whether India’s dams are resilient to climate change as concerns over dam safety have grown in recent times.
India’s dams are old and ageing and there is an urgent need to assess their safety, carry out repairs, or dismantle them to prevent dam failure-related disasters. Quality assurance of dams was once again brought to light after the Tiware Dam breach in July in Maharashtra's Ratnagiri that resulted in the death of at least 19 people.
During a debate on the Dam Safety Bill in the Lok Sabha, Union Jal Shakti Minister Gajendra Singh Shekhawat informed that there were 5,745 reservoirs in the country, of which, 293 were more than 100 years old. The age of 25 per cent of dams was between 50 and 100 years and 80 per cent were over 25 years old.
These dams pose a serious risk due to their ageing and structural deterioration.
An article published in the Economic and Political Weekly in June points out that the scenario will turn alarming as India approaches the years 2025 and 2050: 64 large dams will turn 125 years of age, 301 will turn 75 years of age, 237 large dams will turn 65 years and an additional 496 large dams will cross a minimum age of 50. In all, about 1,115 large dams would have aged at least 54 years by 2025.
“Dams that span decades, experience differential settlement of foundation, clog of filters, increase of uplift pressures, reduction in freeboard, cracks in the dam core, loss of bond between the concrete structure and embankment, reduction in slope stability in earthen and rockfill dams, erosion of earthen slopes, and deformation of dam body itself,” the article says.
Thus, dam components lose strength differently during their lifetime and every component within a large dam ages at a different rate. Hence, as a dam ages, the impact of the erosion of earthen components, through the dam body and foundations, and sedimentation occur at a rate different (or adverse) than what has been assumed by the policymakers and planners.
Experts highlight that dam management in India needs a complete re-look.
“There should be coordination at state and inter-state level for proper management of the dams and how operation of reservoirs should be done. There should be a body to oversee the coordination” said Himanshu Thakkar of SANDRP.
“In the era of climate change, following the rule curve is still more urgent. This is because we do not know when and how the rainfall will increase or decrease,” he added.
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