Ageing Dams – An Emerging Threat

Content:

Highlights of the UN report

• United Nations University’s Canadian-based Institute for Water, Environment and Health released a report titled ‘Ageing water infrastructure: An emerging global risk’
• The report aims to attract global attention to the creeping issue of ageing water storage infrastructure and stimulate international efforts to deal with this emerging, rising water risk.
• Most of the 58,700 large dams worldwide were constructed between 1930 and 1970 with a design life of 50 to 100 years.
• A large concrete dam usually begins to show signs of ageing when reaching the age of 50 years.
• Ageing signs include increasing cases of dam failures, progressively increasing costs of dam repair and maintenance, increasing reservoir sedimentation, and loss of a dam’s functionality and effectiveness
• Such aging structures across the world pose a growing threat because by the year 2050 most people on Earth will live downstream of tens of thousands of dams built in the 20th century.
• The report said that 32,716 large dams (55 per cent of the world’s total) are found in just four Asian countries: China, India, Japan, and South Korea – a majority of which will reach the 50-year threshold relatively soon.

Ageing of dams in India

The following is the list of major dams that are older than 50 years in India:

Dam failures and dam decommissioned in India

• India has a long history and many cases of dam failures. 
• In 1958, the Kaddam dom in Andhra Pradesh broke down.  In 1959, Kaila dam in Gujarat collapsed due to weak foundation. Kodanagar dam in Tamil Nadu failed because of an earthquake

Other notable Dam related tragedies are as below: 

1961 Panshet Dam Tragedy:

• Panshet Dam, also called Tanajisagar Dam, is a dam on the Mutha river about 50 km southwest of the city of Pune. 
• The dam was constructed in late 1950s for irrigation and water supply for Pune
• In its first year of storing water on 12 July 1961, the dam wall burst. 
• It was because of the total absence of reinforced cement concrete (RCC) strengthening in the conduit through the earthen dam
• This caused massive flooding in Pune. An estimated 1,000 people died from it.

1979 Machchhu dam failure:

• The Machchu-2 dam was situated on the Machchhu river.
• On 11 August 1979, the dam burst, sending a wall of water through the town of Morbi in Gujarat, India.
• Estimates of the number of people killed vary greatly ranging from 1800 to 25000 people.
• The failure was caused by excessive rain and massive flooding leading to the disintegration of the earthen walls

2019 Tiware dam failure:

• On 2 July 2019, the Tiware dam failed. During the time it was overflowing after incessant rains the previous days.
• The water flooded at least seven villages situated downstream including Bhendewadi, Daadar, Akle, Riktoli, Ovali, Kalkavne and Nandivase with about population of 3000. 
• Several houses were washed away. At least 19 people died and four more went missing.

Dams and Disaster management

• Dams, and large dams in particular, even if structurally sound, are considered to be “high hazard” forms of infrastructure.
• The consequences of dam failure would be forced displacement, the destruction of livelihoods and potential loss of human life 
• Dam failure mechanisms include seismic activity, flooding, seepage/internal erosion, deterioration, and structural instability.
• Such triggers of failures are more likely in older dams because ageing increases the vulnerability of a dam to such triggers. 
• Also, climate change may accelerate a dam’s ageing process. Extreme weather events, especially floods, are expected to become more severe and frequent with the changing climate.
• Consequently, these events increase the threat to aging large dams designed using historical hydrological data
• Thus, a comprehensive safety review and audit of old dams in India is necessary as a precautionary and preventive measure.
• If a dam is found unsafe, suh dam should be considered for Dam decommissioning.
• Early warning systems and regular checks are also necessary for better preparedness during dam related disasters.

Critical functions of Large Dams in India

The dams and reservoirs world over have been playing a dual role of harnessing the river waters for accelerating socio-economic growth and mitigating the miseries from the vagaries of floods and droughts. 

Dams and reservoirs in India contribute significantly in fulfilling the following basic human needs, in the following ways:

Water for Drinking and Industrial Use: 

• Large dams are the source of water for nearby cities and towns. 
• Many cities are dependent on dams for meeting their drinking water and industrial water requirements.

Irrigation: 

• Using these dams, surplus waters during wet periods are used for irrigating arid lands. 
• Water flows can be regulated as per agricultural requirements of the various regions over the year.
• It is estimated that 80% of additional food production by the year 2025 would be available from the irrigation made possible by dams and reservoirs.

Flood Control:

• Dams and reservoirs are also being used to control floods by regulating river water flows downstream the dam.

Hydroelectric Power Generation:

• Large Dams are used for Hydro Power Generation which provides a cheap, clean and renewable source of energy.
• Hydro Power is the most advanced and economically viable resource of renewable energy.
• Reservoir based hydroelectric projects provide much needed peaking power to the grid.