UN Report on Ageing Dams

UN Report called “Ageing Water Infrastructure: An Emerging Global Risk” highlights a concerning issue. By 2025, more than 1,000 large dams in India will be around 50 years old. This aging infrastructure isn’t unique to India; it’s a global problem. The report, put together by the Institute for Water, Environment, and Health in Canada, suggests that we won’t see a new wave of massive dam construction like we did in the mid-20th century. Instead, the dams built during that era will start showing signs of age. The report also looks at case studies of dam decommissioning and aging in countries like the USA, France, Canada, Japan, and Zambia and Zimbabwe.

Key Points

Global Scenario:

Many of the world’s 58,700 large dams were built between 1930 and 1970 and were designed to last 50 to 100 years.
By 2050, a significant portion of the global population will be living downstream of tens of thousands of these older dams, many of which are already operating beyond their intended lifespan.
When a large concrete dam reaches around 50 years of age, it typically starts showing signs of wear and tear.
These signs of aging can lead to more dam failures, higher costs for maintenance and repairs, increased sediment buildup in reservoirs, and a decrease in the dam’s overall functionality and effectiveness. These issues are closely connected.
Interestingly, 55% of the world’s large dams, which amounts to 32,716 dams, are concentrated in just four Asian countries: China, India, Japan, and South Korea. A significant number of these dams are approaching the 50-year mark.
Similar challenges are also being faced by many large dams in Africa, South America, and Eastern Europe.

Indian Scenario:

India ranks third globally for constructing massive dams.
Out of the 5,200 large dams built, around 1,100 have already celebrated their 50th birthdays, and some are more than 120 years old.
By 2050, we’ll have around 4,400 such aging dams, which means that 80% of our large dams might become outdated, ranging from 50 to over 150 years old.
The situation with hundreds of medium and minor dams is even more concerning, as their lifespan is even shorter compared to large dams.
For instance, the Krishna Raja Sagar dam, built in 1931, is now 90 years old, and the Mettur dam, constructed in 1934, is 87 years old. Both of these reservoirs are situated in the water-scarce Cauvery river basin.

Problems:

Decreasing Storage Capacity: As dams age, soil replaces the water in the reservoirs. Therefore, the storage capacity cannot be claimed to be the same as it was in the 1900s and 1950s. The storage space in Indian reservoirs is receding at a rate faster than anticipated.

Flawed Design: Studies show that the design of many of India’s reservoirs is flawed. Indian reservoirs are designed with a poor understanding of sedimentation science. The designs underestimate the rate of siltation and overestimate live storage capacity created.

High Siltation Rates: It refers both to the increased concentration of suspended sediments and to the increased accumulation (temporary or permanent) of fine sediments on bottoms where they are undesirable.

Consequences:

Decreased Water Supply: When soil replaces the water in reservoirs, it leads to a reduced water supply. This means that the areas used for farming receive less and less water as time goes on.

Impact on Groundwater: As a result, the land available for planting crops either becomes smaller or relies heavily on rainfall or groundwater, which is often overused and depleted.

Farmer’s Income Affected: Farmers may see a drop in their income because water is a critical factor for crop yield, along with factors like access to credit, crop insurance, and investment.

Climate Adaptation Challenge: It’s important to recognize that any plans to adapt to climate change will struggle to succeed if the dams are filled with sediment and not functioning properly.

Increased Flooding: Many reservoirs with designed flood control mechanisms may have lost their capacity over time, leading to more frequent downstream flooding. This has been the case in places like Bharuch in 2020, Kerala in 2018, and Chennai in 2015, where downstream releases from reservoirs contributed to flooding.

Government Action: Recently, the Cabinet Committee on Economic Affairs has given the green light to the Dam Rehabilitation and Improvement Project (DRIP) Phase II and Phase III. This initiative aims to comprehensively repair and upgrade 736 existing dams all over the country and complements the Dam Safety Bill of 2019.

Way Forward

In the 21st century, as our population continues to grow, finding enough water for people, agriculture, cities, and progress will become a major challenge. It’s crucial for all of us to work together to address this issue promptly.
To prevent dam failures, we need a solid safety mechanism. When a dam fails, no punishment can bring back the lives lost, so prevention is key.
We should consider dam decommissioning just as important as building new dams when planning our water storage infrastructure. It’s a part of responsible development.
With our climate changing, it’s more important than ever to think carefully and take proactive steps to manage our water resources effectively.

Read Also: What is Flood Plain Zoning?