River interlinking projects in India may aggravate water stress: Study

New Delhi: India's ambitious river interlinking projects, designed to address the country's increasing droughts and floods, may inadvertently worsen water stress and disrupt monsoon patterns, according to a study published in the journal Nature.

The research used several techniques, including regional climate models and reanalysis data, to shed light on the intricate web of hydro-meteorological consequences that could be unleashed by these massive infrastructure projects.

The researchers, including those from Indian Institute of Technology (IIT) Bombay and Indian Institute of Tropical Meteorology (IITM), Pune incorporated atmospheric variables, accounting for common drivers such as the El Nno-Southern Oscillation (ENSO).

The analysis focused specifically on the summer monsoon season, a crucial period for India's water cycle and agriculture. The study revealed intricate causal pathways between river basins driven by land-atmosphere feedbacks.

These feedback loops create connections between land variables, including soil moisture, and influence the moisture content of the air, temperature, and precipitation in different basins.

Certain river basins were identified as "donor basins" with more outgoing links, while others were labeled "recipient basins" with a higher number of incoming links.

This classification depends on the net transfer of moisture through atmospheric pathways, indicating that some basins contribute moisture, while others receive it.

The study noted both positive and negative land-atmosphere feedbacks between river basins. For instance, soil moisture from one basin could either reduce or amplify soil moisture in another basin, depending on the nature of the feedback.

The research suggests that inter-basin water transfer, as proposed in river interlinking projects, could perturb the land-atmosphere interactions, affecting the moisture content of the air and wind patterns. These perturbations could lead to changes in rainfall patterns across the country.

"The findings of this study carry significant implications for India's massive river interlinking projects," the authors of the study wrote in their paper.

"The proposed projects involve transferring water from surplus to deficit river basins through reservoirs and canals without a comprehensive understanding of the hydro-meteorological consequences," they said.

One of the most concerning outcomes highlighted by the research is the potential reduction of mean rainfall in September by up to 12 per cent in already water-stressed regions of India due to increased irrigation from transferred water, the researchers said.

This could exacerbate water stress across the country, rendering the interlinking projects ineffective or even counterproductive, they said.

The team, which also included researchers from the University of Hyderabad and King Abdullah University of Science and Technology, also observed that La Nina years, which are characterised by cooler sea surface temperatures in the tropical Pacific Ocean, can lead to more severe drying compared to El Niño years, intensifying the challenges posed by interlinking projects.

In light of these findings, the researchers emphasise the need for model-guided impact assessment studies of large-scale hydrological projects, not just in India but across the globe.

Such assessments should consider the intricate land-atmosphere interactions and feedbacks that can influence water availability and climate patterns, they said.

The study underscores the importance of a holistic understanding of the complex hydro-meteorological systems when planning and implementing infrastructure projects that impact water resources.

It urges policymakers and stakeholders to take into account the potential consequences of river interlinking on the country's water security and climate resilience.