A gigantic engineering plan to interlink Indian rivers, first put forth by British colonial rulers, was refined in 2015–16. If executed, it is likely to be the most extensive alteration to India’s hydrology in history. To transfer 174 billion cubic meters of water annually—roughly equal to Pakistan’s annual water use—from areas with an abundance of water to those in need.
The National Water Development Agency, which oversees the river-linking project, intends to build a network of 15,000 kilometers of canals and thousands of reservoirs. The project aims to retain as much water on land as possible to meet the nation’s increasing water demand for irrigation.
According to a paper published in Journal Nature Communications last month, this plan will be controversial for the environment and climate. The water transfer may impact the climatic systems that drive the Indian monsoon, resulting in a 12% decrease in September rainfall in some States.
A few scientists have advised against implementing the river engineering project since there is insufficient information regarding how it will shape future environmental conditions. Additional research has evaluated the project’s possible effects, such as silt deposition and the impact on aquatic ecosystems. According to Dr Subimal Ghosh, one of the study’s authors and a climate scientist at the Indian Institute of Technology Bombay, the water cycle involves interaction between atmospheric moisture, oceans, plants releasing moisture, and climactic patterns. The research team aimed to study how a river basin in one region impacts atmospheric processes and, therefore, impacts other areas as well.
Increasing the area under irrigation by 35 million hectares is one of the main goals of the river-linking plan. Higher amounts of evapotranspiration—releasing leaf moisture—would result in more crops. Local temperatures would drop, rainfall patterns would alter, and clouds would form in response to increased atmospheric moisture. The researchers examined the interactions between rainfall, humidity, soil moisture, temperature, and wind speed in seven river basins during the monsoon season, which runs from June to September, using computer modeling.
The research further showed that when crops reach maturity and evapotranspiration rises in September, the impact of the land-atmosphere interaction is most significant. As a result, the states of Rajasthan, Gujarat, Odisha, and Andhra Pradesh saw a 6.4%–12% decrease in September rainfall. The north-eastern states of Bihar and Jharkhand and the central regions of Maharashtra and neighbouring Telangana showed increases in September precipitation of up to 12% and 10%, respectively. So, less rainfall will reduce river flow in the following months, which might worsen water stress in already parched areas such as Rajasthan and Gujarat. The influence of fresh river water flowing into the ocean, which can potentially affect monsoon rainfall, is not considered by these impacts. In brief, the researchers argue that the river linking may considerably reduce or neutralize the claimed benefits envisaged in the original plan.
