The National River-Linking Project is the world’s most ambitious project of its kind to date, proposing to link 37 major river basins across India using 30 links, potentially redistributing around 174 billion cubic metres of water from ‘surplus’ to ‘deficit’ basins while generating some 34,000 MW of power.
Yet the Project has also raised serious concerns about its environmental costs. Experts have said the idea of ‘surplus’ and ‘deficit’ basins can mask seasonal and year-on-year variations in river flows, and that transferring water between basins can alter downstream flows, sediment transport, floodplains, deltas, and the habitats that depend on them. Dams, reservoirs, and canals can also break ecosystems up into pieces and disturb fish migration and other ecological processes.
Climate change has also been complicating assumptions about how much water a basin will reliably have available to transfer in the decades ahead. But it seems river-linking also poses another, less obvious problem.
‘Ecological highways’
Recently, researchers from the Ashoka Trust for Research in Ecology and the Environment (ATREE), Bengaluru, assessed the Project also possibly creating “ecological highways” that invasive species can travel on to new, ecologically sensitive areas.
Their findings were recently published in Scientific Reports.
Because of the ways in which India’s river basins are isolated from each other, many species in each one are endemic, meaning they inhabit a small area and are not found elsewhere on the planet. River links may then threaten them more than native species.
“There is no public or verifiable scientific basis that backs any of the claims of benefits of the National River-Linking Project, but more of a notional basis that if you connect a drier part to a wetter part of the country, there will be water balance, as opposed to how ecology actually works,” Siddharth Agarwal, director-founder of the Veditum India Foundation, a nonprofit working on environmental governance, said.
In the paper, the team showed that all Northeast and peninsular Indian basins are more vulnerable to biological invasions than those in Central and North India.
The Southwestern Ghats, Kaveri, Krishna Lower Ganga, and Brahmaputra basins support diverse habitats and complex ecological niches that host native species, threatened species, and invasive alien species.
‘Invasion hotspots’
“Right now, [the invasive alien species] are isolated, restricted to individual river basins,” the study’s lead author and ATREE senior fellow Aravind Neelavar Ananthram said. “By connecting rivers, we would not only introduce new species which are not naturally found but also increase the vulnerability of the native species that cannot compete with the invasive alien species.”
This finding is consistent with research worldwide, which has suggested that biodiversity hotspots can accumulate more invasive alien species, thus compromising the long-term prospects of native species and themselves turning into ‘invasion hotspots’.
For example, the Lower Ganga basin hosts 13-15 invasive alien species, and could become a major source of invasives for the Mahanadi, which is home to 69 threatened species. In fact, this is one of the Project’s most ecologically sensitive links, and it could increase the risk of extinction for the threatened species.
Water connections under the Project could also help aquatic pathogens to spread, disrupt the migratory routes of fish, and flatten the unique biota that individual river basins boast today.
“Fishes in one river basin may be well adapted or immune to the pathogens it harbours, while species in other basins may not be able to protect themselves against such pathogens,” Dr. Ananthram said. “If one reduces the water flow by taking out water from one river and putting it into another, the downstream water flow will be reduced. As a consequence, the downstream biodiversity will be severely affected and there is a high chance that the endemic species in the lower reaches might go extinct.”
“The river linking project is being sold as a solution (at least for the Ken-Betwa) to water scarcity (in Bundelkhand), but can it really serve the objectives that it is proposing?” Mr. Agarwal asked. “There is no way for us to verify. It is more of a capital investment than an ecological one.”
In need of foresight
“Rivers like the Ken have sand of great ecological value. But when the Ken-Betwa link is live, large quantities of water will be moved away from the river, lowering the flow volume and reducing sediment production rates in the river,” Mr. Agarwal said. “That could ultimately reduce the biodiversity in the river and potentially even trigger a food chain collapse.”
The Project’s consequences may also extend to downstream nations.
“Right now, we have only considered 15 freshwater invasive species for which data is available,” Dr. Ananthram said. “If one looks at all species across India, including terrestrial and marine systems, it would be approximately 350 to 400 species in different stages of invasion. Developed economies like Australia and in Europe have very strong policies for invasive alien species. It is an urgent need that India comes up with a specific policy targeted to regulate, manage and control” such species.
Embedding evidence-based management of river basins into national infrastructure planning could provide ecological foresight.
“The health risks, biodiversity, wildlife, and economic costs of [the Project] to India, especially for the agro-economy, farmers’ livelihoods, and fisheries, are matters of urgent attention,” he added. “While the government’s intention might be good to address water deficit, development plans and policy decisions should be holistic, addressing the ecological impact, the effect on biodiversity, and people’s lives.”
Jhinook Mitra is an independent researcher and ecologist, currently with the Nature Conservation Foundation, Bengaluru.
Published – September 30, 2026 09:15 am IST
