- New research finds that river interlinking could lead to a decrease in rainfall in September in dry regions of India.
- The study shows that changes in soil moisture from one river basin can affect soil moisture in neighbouring basins, leading to changes in precipitation patterns.
- Experts say that climatic impacts need to be factored in at the planning stage of river interlinking projects.
On October 3, the Ministry of Environment, Forests and Climate Change awarded the Ken-Betwa river interlinking project final forest clearance, six years after it was given ‘in principle’ approval. For decades, river interlinking has been extolled as an engineering marvel that could irrigate drought prone regions and do so, cost-effectively. Claims about the Rs. 44,000 crore Ken-Betwa project are no different. But new evidence suggests large scale river interlinking could have unintended consequences on rainfall patterns and urges policymakers to think more deeply about altering a river’s course in a changing climate.
Ever since it was proposed, river interlinking in India has been fraught with disagreements among many stakeholders. Much of the criticism arising from river interlinking has been rooted in its terrestrial effects. Environmentalists and activists have argued that river interlinking could change groundwater levels, introduce alien invasive species and reduce sediment deposits downstream, among other ecological concerns. In the case of the Ken-Betwa interlinking project – the first of 30 such projects to reach the implementation stage – 10 percent of the Panna Tiger Reserve stands to be submerged. Around 6,809 hectares of forest land will be diverted for the project, according to government documents.
Now, new research from the Indian Institute of Technology, Bombay, considers what the possible impacts of moving vast amounts of water could be on atmospheric feedback loops that regulate evapotranspiration and precipitation. “This research introduces a new dimension to the challenges of river interlinking,” said Jagdish Krishnaswamy, an ecohydrologist and dean of the School of Environment and Sustainability at the Indian Institute for Human Settlements (IIHS).
The paper finds that such movements through river interlinking can lead to a deficit in rainfall by up to 12 percent in already water stressed regions, when the monsoon is withdrawing in September.
River linking has historically been proposed as a solution to enduring drought in various regions across the country. Instead, the paper notes, river interlinking could “dry up the rivers in the subsequent months (after September) amplifying water stress manifolds in various parts of the country.”
On October 19, the National Water Development Authority, which is overlooking river interlinking in India, held its fifth meeting on the Ken-Betwa river interlinking project. Mongabay India reached out to Bhopal Singh, director general of the National Water Development Authority for his comments on the paper over email. There was no response till the writing of this story.
12 percent decrease in rainfall, says study
The National River Linking Project was first proposed in 1980, with the aim of transferring water from “surplus” river basins to “water-deficit” ones to improve irrigation along drought prone tracts. Of the 30 basins identified for interlinking, 16 are in peninsular India and 14 in the Himalayan region. Together, these projects would transport 174 billion cubic meters of water each year through a network of canals.
“The idea of this paper didn’t come from river interlinking per se,” said Subimal Ghosh, a researcher from IIT Bombay and co-author of the paper, which was published in the journal Nature on September 22. “Previous research we had done showed that changes in water (irrigation) practices, over a large scale, had an impact on the monsoon and so we decided to explore that further to see what could happen with river interlinking.”
The paper looks at land and atmospheric variables such as soil moisture, heat, humidity, precipitation and wind speed, among others, to project what changes might occur if river interlinking is undertaken. The results of the study work under the assumption that all projects are completed, and it finds that while rainfall remains largely unaffected in the months of June, July and August, there is a statistically significant decline in September across several rain-fed regions.
The highest median reductions in rainfall in September were found to be in Odisha (12 percent), Andhra Pradesh (10 percent), Rajasthan and Gujarat. (9 percent). Parts of central India in the core monsoon zone also show a decline in rainfall of 8 percent, along with declines in the western Himalayan foothills in Uttarakhand and east-central India (6.4 percent).
Ghosh explains that these changes are triggered by changes in soil moisture. “When soil moisture is changed in one basin, it can cause changes in neighbouring basins by affecting evapotranspiration, cooling and precipitation. We find that river basins are linked to each other by these feedback loops,” he said. According to the paper, increased moisture in the soil can supply moisture to the atmosphere by evapotranspiration, which can either lead to recycled precipitation in the same basin or can get transported to faraway regions by the wind.
The cooling resulting from the evaporation can cause fluctuations in temperature across different land regions, “changing wind patterns and, subsequently, the moisture transport and rainfall,” says the paper.
While rainfall is projected to decrease in drier regions, some regions are expected to see a rise in rainfall in September, such as the states of Bihar, Jharkhand, and eastern Uttar Pradesh (12 percent increase), as well as some parts of Maharashtra and Telangana (10 percent).
Far from distributing soil moisture equally across all basins, river interlinking could create greater imbalances, says the study, because rivers don’t share the same balance of linkages to land, ocean, and the atmosphere. River interlinking could increase soil moisture in the Krishna basin, the western portion of the Godavari and Narmada-Tapi basins, and the eastern Ganga basin. But there is a “pronounced decline in soil moisture of the Mahanadi, Godavari, and western part of Ganga basin in Indian states of Odisha, Chhattisgarh, northern Maharashtra, Madhya Pradesh, and Rajasthan,” says the study.
“The atmosphere is as important a component as land in the water cycle. The role it plays when there are changes to land and water use should be considered when designing projects like this, so the impacts can be managed,” said Ghosh.
According to Krishnaswamy, this paper’s findings coupled with a 2018 paper on the effects of river interlinking on downstream sedimentation “give enough reason to seriously question the benefits of interlinking.” The 2018 paper by scientists at the University of Colorado found that river interlinking could decrease silt deposition in the Ganga and Brahmaputra deltas by 30 percent, making the area more vulnerable to sea level rise and coastal erosion. It also found that discharge from 24 out of 29 rivers assessed would decrease, which “may damage wetlands and contribute to the deterioration of freshwater and estuarine ecosystems.”
The IIT Bombay paper relies on rainfall data from 1991 to 2022 and compares the outcomes of river interlinking with current patterns of precipitation. It does not, however, factor in the future effects of climate change over the country. “We aren’t exactly clear about the effect global warming will have on the Indian monsoon, so we have only used the present case scenario for our study. But what we’ve seen over the last 50 to 70 years is that there has been a decline in the monsoon,” said Ghosh, adding, “Before modelling for the future, it’s important to see that the climate change projections are reliable.”
Status of river linking
Despite being conceived decades ago, progress in implementing river interlinking has been slow, with many disputes along the way. In the plan to link the Godavari river with the Kaveri, states have raised concerns about the availability of water in the former to divert to the latter and called for reassessments of the water basin capacity. This linkage, which involves three components across the states of Telangana, Andhra Pradesh, Karnataka, Tamil Nadu and Chhattisgarh, is still stuck because there is no consensus yet on the water sharing agreement between states.
A.K. Bajaj, former chairman of the Central Water Commission, told Mongabay India that it was not necessary that all 30 river interlinking projects would go through, in light of the disagreements between states on the water available in rivers.
The Ken-Betwa river linking plan is the first to reach the implementation stage, after Madhya Pradesh and Uttar Pradesh signed an agreement in 2021 and the project received Cabinet approval. The forest clearance awarded earlier this month, however, comes with 46 conditions attached. According to a recent news report by the Indian Express, the project’s wildlife clearance is still under dispute in the Supreme Court and it may need fresh environmental clearance before it is implemented on the ground.
“We may not see the kind of results the IIT Bombay study is projecting because not all states may agree to river interlinking,” said Bajaj, adding, “The interlinking project will also result in many storage dams, which can help tide over periods of drought or reduced precipitation.”
Banner image: Betwa river flowing through Ashoknagar in Madhya Pradesh, near the Uttar Pradesh border. Photo by PankajSaksena/Wikimedia Commons.