Context

• A parliamentary panel has expressed concerns over the safety of ageing dams in India.
• The Standing Committee on water resources, in its 20th report, has raised the issue of safety risks posed by more than 200 dams in the country.

Central idea

• Citing the National Register of Large Dams 2019, the panel says there are 234 large dams in India which are 100 years old – and still functional.
• Dams are normally designed for approximately 100 years of useful age.
• Their functional life gets decreased with progressive reservoir sedimentation concurrently reducing project benefits – is what has been submitted by the parliamentary panel in its report.

Ageing Dams of India

• India has 4,407 large dams, the third highest number in the world after China (23,841) and the USA (9,263).
• Over 1,115 large dams will be about 50 years old by 2025.
• In less than 30 years, by 2050, over 4,250 large dams would pass 50 years of age, with 64 large dams being 150 years old, cited a 2019 paper published in the Economic & Political Weekly.

Why discuss Dams?

• Cost overruns: The construction of dams can be expensive, and cost overruns are common. This can lead to delays in construction, reduced funding for other projects, and higher costs for consumers.
• Environmental damage: Dams can cause significant environmental damage, such as altering the natural flow of rivers and altering habitats for fish and wildlife. The creation of reservoirs can also lead to the loss of forests and other important ecosystems.
• Water scarcity: While dams can provide a source of water for irrigation, drinking, and other purposes, they can also lead to water scarcity downstream. The reduced flow of water can affect agriculture and the livelihoods of those who rely on rivers for their water supply.
• Seismic activity: The construction of large dams can sometimes trigger seismic activity in the surrounding area. This can lead to landslides and other types of damage.

Social Impacts of Dams

• Displacement: Dams often result in the displacement of people living in the area. The displaced people are forced to leave their homes and land, which disrupts their livelihoods and cultural practices.
• Dismay over resettlement: This is often promised as a means to compensate for displacement, is not always met.
• Cultural loss: The construction of dams often involves flooding of large areas, which can lead to the loss of cultural heritage sites and artifacts.  
• Environmental Impacts: Dams can have a range of environmental impacts, such as altering the natural flow of rivers, disrupting the habitats of aquatic species, and changing the water temperature and chemistry.  
• Economic Impacts: There may also be a loss of economic opportunities due to the displacement of people and disruption of traditional livelihoods.
• Health Impacts: These may include the spread of waterborne diseases due to changes in water quality, increased incidence of malaria due to the creation of stagnant water, and respiratory illnesses etc.

Woes of Ageing Dams

(1) Faster Rate of Storage Loss

• As dams age, soil replaces the water in the reservoirs, causing the storage capacity to decrease.
• In India, the storage space in reservoirs is receding at a faster rate than anticipated, with some reservoirs expected to become extinct in a few decades.
• The iconic Bhakra dam’s siltation rate is 139.86% higher than originally assumed, causing it to function for only 47 years instead of the estimated 88 years.

(2) Impact of Climate Change

• The increasing frequency and severity of flooding and other extreme environmental events can overwhelm a dam’s design limits and accelerate the ageing process.
• For example, development of crack on empty dams’ wall.

(3) Structurally vulnerable dams

• Most Indian reservoirs are designed with a poor understanding of sedimentation science, which can make them structurally weak over time.
• Large storage structures, whether concrete, masonry, or earth, can become vulnerable with age.

(4) Lack of storage information

• The loss of large dams’ storage capacity over time is part of the ageing process. Sort of river rejuvenation also changes the dam topography.
• However, this information continues to be sporadically documented in India, which makes it a blind spot in terms of understanding the water crisis in the country.

Issues related to Ageing Dams

• Decreasing Storage Capacity: As dams age, soil replaces the water in the reservoirs, leading to decreased storage capacity over time. This is a common problem faced by dams all over the world. In the case of Indian reservoirs, the storage space is receding at a rate faster than anticipated.  
• Design flaws: Many of India’s reservoirs are designed with a poor understanding of sedimentation science, leading to flawed designs. The designs underestimate the rate of siltation and overestimate the live storage capacity created.
• High Siltation Rates: High siltation rates refer to both the increased concentration of suspended sediments and the increased accumulation of fine sediments on bottoms where they are undesirable. This leads to the reduction of the storage capacity of the reservoirs and can have a detrimental effect on the functioning of the dam.

Consequences of Ageing Dams

The ageing of dams can have a significant impact on various aspects of life, including food security, farmers’ income, and increased flooding.

• Impact on food Security: As soil replaces the water in reservoirs, the supply gets choked, leading to less and less water for cropped areas. This can cause the net sown water area to either shrink in size or depend on rains or over-exploited groundwater, which can have an impact on food security.
• Impact on farmers’ Income: As crop yields may get affected severely, this can disrupt the farmer’s income. Water is a crucial factor for crop yield and credit, crop insurance, and investment. Therefore, the ageing of dams can have a significant impact on the livelihoods of farmers.
• Increased flooding: The flawed siltation rates reinforce the argument that the designed flood cushion within several reservoirs across many river basins may have already depleted substantially. This has led to floods becoming more frequent downstream of dams.  

Policy measures so far

(1) Dam Rehabilitation and Improvement Project (DRIP)

• The DRIP was initiated in April 2012 to improve the safety and operational performance of selected existing dams along with dam safety institutional strengthening with a system-wide management approach.
• Financial assistance for DRIP was provided by the World Bank. The budget outlay for DRIP is Rs 10,211 Cr, which includes rehabilitation provisions for 736 dams.
• The project is being implemented in three phases with a budget outlay of Rs 5,107 Cr each for Phase II and III.

(2) Dam Safety Act 2021

• The Dam Safety Act 2021 is a significant step taken by the government towards ensuring the safe functioning of all specified dams in the country.
• The act provides for proper surveillance, inspection, operation, and maintenance of dams to ensure their safe functioning.
• It also includes the establishment of the National Dam Safety Authority as a regulatory body and the constitution of a State Committee on Dam Safety by the State Government.

Way forward

• Timely reviews: Review dams that have reached 50-60 years of age to assess their safety and take an informed decision.
• Decommissioning: This should be given equal importance as dam building in water storage infrastructure development. Projects that pose serious safety risks should be listed and decommissioned in a phased manner.
• Accountability and Transparency: Ensure accountability and transparency while taking into consideration the views of downstream communities, the most at-risk group in case of a breach.
• Operational safety and drills: Update the rule curve, which decides how a dam should be operated, at regular intervals based on environmental changes like siltation and rainfall patterns that would change the frequency and intensity of incoming floods and the spillway capacity.
• Cumulative Assessment: Conduct a cumulative assessment of every upstream and downstream dam to ensure dam safety in terms of operations. 

Some major dams in India