Let’s start with some statistics first : India has over 5000 dams and reservoirs that can store around 257 billion cubic meters (BCM) of surface water per year which is ~40% of its annual water consumption . Present day availability is ~694 BCM which includes stored surface water and renewable ground water and not surprisingly our growing population will have a water demand that would almost double to ~1180 BCM by year 2050 with demand exceeding supply by two times.
Dams are engineered structures that have several purposes: water storage, agricultural irrigation, flood control, hydro power generation, as a recreation site to name a few. Hydropower is the world’s most reliable and renewable source of electricity and dams store river water which, when released, powers turbines and generators to create electricity.
Aging dams and flash flooding accelerated by climate change are a looming threat to our ecosystems, questioning dam sustainability
Why are dams seeming unsustainable?
Several important dams in India were built during the 1970s and are aging, in need of repair, rehabilitation or even decommissioning (dam removal having outlived their purpose).
Siltation: Sedimentation or gradual accumulation of soil in dams and reservoirs especially downstream results in reduced storage capacity. As an example, Bhakra dam in Himachal Pradesh, has a siltation rate 140% higher than when planned in 1963. Given the excess silt formation, the dam’s expected lifespan was for 47 years instead of the original estimate of 88 years which meant that Bhakra dam would have to be decommissioned by 2010. Every year, de-silting measures and dredging of the soil sediments is a continuous, expensive, and laborious maintenance process to keep these dams operational.
Environmental and social concerns: Dams disrupt flow of rivers, block seasonal flood patterns and its negative impacts on river ecosystems have worsened over the years. Dam failures have displaced millions of people, mostly tribals and submerged entire villages and towns.
The Uttarakhand tragedy in Feb 2021 due to Himalayan glacier melt resulting in flash floods not only killed several people but washed away two power projects generating hydroelectricity, destroyed Dhauliganga dam and emptied downstream dams to stop floodwaters reaching towns of Haridwar and Rishikesh.
More recently in March 2021 , Australia’s Warragamba dam started to overflow spilling water ( around 550 gigalitres/day about twice the average daily flow of Niagara Falls) resulting in evacuation and extreme flooding . What could have possibly prevented the spillover was keeping space in the dam for flood mitigation, but the dam’s main purpose as Sydney’s drinking water supply and keeping it full resulted in escape routes for water flooding the city and suburbs.
And, how can we forget activist Medha Patkar’s courageous fight to save the Narmada river from the Sardar Sarovar dam in Gujarat resulting in the Supreme court ruling in 2000 to stop work at the dam and cancelling World Bank’s loan to further increase the height of the dam. Sadly, displacement and rehabilitation of the tribals and villagers in the surrounding areas have been inequitable and forced relocation of thousands of people has created social unrest.
Until the early 2000s, dam inspections were minimal but with extreme weather and numerous dam disasters, dam safety came back to focus. Inspections found that a third were unsafe and states began to take their dam safety responsibilities seriously. One sure way to eliminate a dam’s danger is to dismantle it but removing a dam can cost as much as building the dam in the first place.
Incorporation of climate change into dam safety practices still has several challenges as the predictive science that can quantify frequency and intensity of flooding is still not advanced. Dam safety officials typically take decisions to release water based on readings of precipitation that has already occurred and technologies for forecasting of extreme events and flash flooding is being implemented in pilots. The Dam Rehabilitation and Improvement project(DRIP) of India has its objectives focused on improving safety and performance of key dams in a sustainable manner. Take a look at this dashboard that gives a picture of India’s dams , expenditure on dam safety and upkeep guidelines.
Are there alternatives to dams?
If we are thinking about dams mainly built for hydroelectricity generation, the alternatives are many: wind, solar, nuclear, bio-mass energy, small scale hydro-projects that run on river’s natural flows.
Sub-surface dams and coastal reservoirs are built to store natural flow of water near the riverbeds of seasonal rivers. Japan’s Fukuzato underground dam is a great example that saves water being wasted into the sea. Ananganandi dam in Kerala, Bhujpur underground dam near Mundra in Gujarat are good case studies of sustainable water projects that highlight the advantages of limited evaporation loss, no siltation, less susceptibility to pollution, no big dam failure disaster, no land submergence, and resettlement associated with surface dams.
America is dismantling dams faster than ever and looking at restoring free-flowing rivers because of its environmental value.
In conclusion : for developing countries like India, the need for construction of additional large dams to support and sustain economic development will remain. We need to find better ways to plan, build, and operate dams, reservoirs, and hydropower stations in a manner that their negative impacts on environment and society can be reduced.
Dams are erected assuming they would be eternal, would not fail, never be filled with sediments and be financially viable. Yet, all dams disintegrate eventually by the power of nature. Planning water administration of large river basins, inter-basin water planning, diversified sources of water management and careful decommissioning of dams can reduce huge costs related to people displacement, environmental damages and enhance resilience against negative impacts of climate change.