India built thousands of dams in the last century to secure water, generate power, and control floods. But many of those lifelines are now choking on silt and Madhya Pradesh is at the centre of this crisis.
A new scientific study from the Indian Institute of Science Education and Research (IISER), Bhopal, has found that large reservoirs across India have already lost nearly half their designed storage capacity due to rising sedimentation. The study, published in the journal Stochastic Environmental Research and Risk Assessment, analysed over 300 major reservoirs and warned that, at the current rate, many could fall below 50 percent capacity by 2050.
While the problem spans the Himalayas to the Western Ghats, the Narmada basin in Madhya Pradesh shows how sedimentation is compounded by local human pressures, especially rampant sand mining. Since 2015, illegal extraction has surged, altering river flows, worsening erosion, and threatening reservoirs that are already losing storage space.
“Farmers who once grew melons and cucumbers on the sandy banks have lost their livelihoods. Fishers report smaller catches, and birds that nest in the sands are disappearing,” said an activist from the Narmada valley. Despite repeated bans by the National Green Tribunal, mechanised mining continues, deepening both ecological and social stress.
The findings show a steep decline in usable water storage. By 2050, even the largest reservoirs in regions such as the Himalayas, the Narmada-Tapti Basin, the Western Ghats, and the Indo-Gangetic Plains are projected to fall below half their original capacity if no action is taken.
The Narmada basin in Madhya Pradesh also shows how reservoir sedimentation links with other pressures on rivers. In Madhya Pradesh, large-scale sand mining has surged since 2015, with illegal operations dwarfing legal ones. This extraction alters river flow, worsens erosion, and threatens the same reservoirs already losing storage.
Farmers who once grew melons and cucumbers on sandy banks have lost their livelihoods. Fishers report smaller catches, while birds that nest in the sands face shrinking habitats. Despite bans by the National Green Tribunal, mechanised mining continues, deepening both ecological and social stress in the basin.
Debris Carried By Rivers
Sedimentation occurs when soil and other debris carried by rivers settle in reservoirs, reducing the space available to store water. Agriculture-related soil erosion, widespread deforestation, and heavy floods are the main drivers behind the rising silt deposits.
“This is not a problem of the distant future. It is already here. Many reservoirs are losing more than 50 percent of their rated capacity,” said Dr. Somil Swarnkar, assistant professor at IISER Bhopal, who led the study.
Swarnkar explained that India’s Dam Safety Act of 2021 mainly focuses on the strength of dam structures, such as walls and gates. But his research team points out that safety also depends on whether a dam can perform its functions.
“A reservoir that loses half its storage may not collapse, but it becomes functionally unsafe because it cannot provide water, regulate floods, or generate power for the people who depend on it,” Swarnkar said.
India is the third largest dam-owning country in the world, after China and the United States. It has about 5,700 large dams. Many of them are ageing. Around 80 percent of large dams in India are already more than 25 years old. Experts warn that this ageing infrastructure, combined with rising sedimentation, poses new risks.
Another concern is seismic vulnerability. Several large dams are located in earthquake-prone areas, raising questions about long-term safety. Financial constraints also affect regular maintenance and monitoring of these structures.
A Warning from Madhya Pradesh
In Madhya Pradesh, the Gandhi Sagar dam on the Chambal river, one of five reservoirs of national importance, shows how ageing structures and poor maintenance can add to risks. Built in 1960, it has faced repeated breaches and floods in recent years. A 2021 report by the Comptroller and Auditor General flagged choked drains, non-functional instruments, and absence of regular checks.
The dam was placed in Category II, meaning it has deficiencies that need urgent attention. But many recommended repairs were delayed or ignored. Millions of people in downstream districts like Sheopur, Morena and Bhind face heightened flood danger during heavy rains. Experts warn that without proper monitoring and timely action, both structural failure and mismanagement in operations could trigger disasters.
The IISER Bhopal team developed a vulnerability index based on sedimentation data. Using long-term government records and statistical modeling, the study identifies the dams most at risk. Several well-known projects already face severe storage losses.
The Chamera-I dam in Himachal Pradesh, commissioned in 1994, has suffered significant storage loss due to steep terrain and heavy monsoon rains. The Salal dam in Jammu and Kashmir, operating since 1987, shows very high vulnerability because of continuous siltation. Older reservoirs like the Nizamsagar in Telangana, built in 1930, now face critical threats to their usefulness.
“This is a silent process. Sedimentation does not make headlines the way a flood or a dam breach does, but its impacts are just as damaging in the long run,” Swarnkar said.
Expert views
The study has drawn attention from researchers working on water and river systems across India. Professor Rajiv Sinha, from the Department of Earth Sciences at IIT Kanpur, described the findings as both timely and actionable.
“This study is highly useful for government agencies. It gives them a clear idea of where they need to focus, whether it is management, safety assessment, or reducing ecological impacts. The data-driven approach makes it reliable for policy planning,” Sinha said.
Experts agree that India must move beyond seeing dams as permanent assets. Sedimentation, if unchecked, can undermine decades of public investment in water infrastructure.
The problem is not confined to India. A 2023 study by the United Nations University Institute on Water, Environment and Health warns that around 3,700 dams in India will lose 26 percent of their total storage by 2050 because of sedimentation. Globally, nearly 50,000 large dams have already lost up to 19 percent of their capacity, and by mid-century the loss is expected to reach 26 percent. That is equivalent to the annual water use of India, China, Indonesia, France, and Canada combined.
The Central Water Commission had reported similar concerns in 2015, noting that one quarter of India’s 141 oldest reservoirs had already lost 30 percent of their storage. Compared to China, which is projected to lose about 20 percent by 2050, India faces sharper risks. Researchers say this puts millions at greater risk of water shortages, power deficits, and flood damage.
“Without proactive management, reservoirs that communities rely on will choke with silt. By 2050, many may no longer serve their intended purpose, leaving millions exposed to water shortages, power crises, and more frequent flood disasters,” Sinha added.
When Dams Fail People
The decline in dam capacity is already affecting people. Hydropower plants linked to silted reservoirs generate less electricity. Farmers in drought-prone regions are struggling with reduced irrigation water. Flood-prone districts face higher risks when reservoirs cannot buffer excess rainfall.
For example, residents near the Kaddam reservoir in Telangana report reduced water supply for both drinking and farming. Built in 1958, the reservoir has been flagged as highly vulnerable due to degraded catchments.
Communities in Bihar also face similar challenges. The Chandan dam, built in 1967, has suffered severe siltation. Local residents say floods have become more frequent in recent years, and the reservoir does not hold as much water during dry months.
The IISER study recommends a range of measures to slow down sedimentation and restore storage capacity. These include afforestation in catchment areas, soil conservation practices in farmland, construction of small check dams to trap sediment upstream, and the installation of sediment flushing systems in existing reservoirs.
Regular hydrographic surveys, detailed studies of water depth and sediment buildup, are also seen as essential for long-term monitoring.
“These interventions are not optional. They are critical if we want to safeguard water security and energy supplies for the coming decades,” Swarnkar said.
Government agencies have acknowledged the scale of the challenge. The Central Water Commission has previously reported sedimentation as a growing concern, though its estimates are often based on limited survey data. The new IISER study adds statistical rigor and a national-level perspective to the debate.
Rethinking India’s Dam Future
India has also promoted small hydropower projects (SHPs) as a cleaner and less disruptive alternative to large dams. With capacities ranging from 2 to 25 megawatts, these projects are often seen as sources of local employment and rural electricity supply. Because they involve smaller submergence areas and little displacement, they are frequently classified as low-impact.
But ecologists caution that the reality can be different. A 2016 report found that small dams, especially when built in clusters, can cause significant ecological harm. Their research showed that SHPs fragment forests, alter river flow, and reduce fish diversity in the Western Ghats. They warned that for every kilowatt of power generated, small dams can damage river ecosystems as much as large ones.
The study also noted that many SHPs in India bypass environmental impact assessments because of policy exemptions. This has allowed several projects to come up in biodiversity-rich regions without proper scrutiny. Scientists argue that cumulative assessments, considering all dams within a river basin, are needed before expanding such projects.
India’s dependence on large dams is set to continue as demand for water and power rises. But the current findings underline the need to rethink long-term strategies. Building new dams may not solve the problem if existing ones are left to choke with sediment.
“The message is clear: dams are not forever. They require continuous management, not just construction and structural checks. If we fail to act, we will face severe consequences by mid-century,” Swarnkar said.
For millions of households, the issue is not academic. Reduced dam capacity could mean fewer hours of electricity each day, crops lost to drought, and lives endangered during floods. The sediment quietly filling India’s reservoirs is already reshaping how these massive structures serve the country.
The IISER study calls for urgent cooperation between scientists, engineers, and policymakers. Without such steps, India risks losing half the capacity of its most critical reservoirs within a generation, a loss that will directly touch every aspect of daily life, from drinking water to food and electricity.
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