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The river linking project of India may lead to up to 12 per cent reduction in rainfall in the month of September due to land atmospheric changes, a recent study has claimed.
Published in Nature Communications, the study through a computer modelling postulates an upset in the rainfall pattern with its impact upon several factors controlling the rainfall, such as atmospheric temperature, moisture in air, and wind speed.
India has long been mulling linking several of its rivers to offset its rainfall deficit and diverting water from surplus river basis to deficit river basins. The proposal was first mooted in the 19th century by a British colonial officer to bring water to the drought-prone southern region from the north where flooding was frequent. The idea has come a long way since with at least 30 river links already identified for feasibility report.
The grand project currently under various stages, from consultation to construction, aims to "keep the maximum possible water — which earlier used to reach oceans from river basins — on the land to meet the growing water demand of the country."
According to the Indian government's National Water Development Agency, the interlinking of rivers will lead to supply of irrigation water to an additional 35 million hectare of land – 25 million ha surface water and 10 million ha of ground water – increasing the total area under irrigation up from 140 million hectare at present to 175 million hectare.
The project involves linking of several rivers that flow through the northern Himalayan region and southern peninsular region of the country. The project that dates back to 1970s in its conceptualisation has been championed by almost all governments at the Centre that have come since, despite states' and activists' demurrals on several of its key points and claims.
The project has not been without its critics, with some studies claiming that such a move may lead to an adverse impact on the behaviour of aquatic creatures.
The present study conducted a computer simulation to predict a change in land’s atmosphere and its consequent effect on the rainfall pattern across the country.
The researchers studied the rainfall in months of June, July, August, and September, and considered variables such as latent heat, temperature, precipitation, relative humidity, and wind speed, to name a few.
"The results from these simulations show a systematic reduction of mean September precipitation of up to 12% in the western arid region (states of Rajasthan and Gujarat), central (state of Madhya Pradesh), central-eastern (states of Odisha and Chhattisgarh) and northern (states of Punjab, Haryana, and Uttarakhand) parts of India, which, based on our experimental setup, can be attributed to land-atmosphere feedback from interlinking," the study says.
The interlinking of river involves supplying surplus water from some rivers, called donor rivers, to those with deficit water, called recipient rivers. But this shifting is not without its consequences, according to the study.
"The perturbed hydrological processes of the receiving river basins send feedback to the Indian monsoon, potentially changing the spatial patterns, specifically in September. Such changing patterns of monsoon, in turn, affect the hydrology of the neighbouring basins," it says.
The researchers cite other studies to claim that this interlinking could particularly impact India, where land feedback to atmosphere has seen to be high.
"So far, no scientific studies have explored the possibility of feedback from the inter-basin water transfer to the water cycle. We hypothesize that the water transfer may impact the donor or adjacent basins through land-atmosphere feedback. Such possibilities could be high in the Indian region, where the land feedback to the atmosphere is also high," it says.
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