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The links between air pollution in Delhi and the water crisis in India

  • The links between air pollution in Delhi and the water crisis in India

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Air quality is a big problem in India’s capital city Delhi every year as the winter starts. Last November was no exception and high air pollution levels led to partial lockdowns and school closures. In a new BBC article, climate and water expert Mridula Ramesh explores the links between Delhi’s smog and the water crisis in India.

Air pollution worsens in the winter months in cities across the world; some factors to blame for it are temperature inversions that trap pollution close to the ground, and increased burning of fossil fuels for heating. Those causes add to year-round sources such as vehicle and industrial emissions.

But in Delhi and much of northern India, more factors come into play: dust storms, firecrackers during the Diwali festival, and crop fires. Both the firecrackers and crop fires play a large role; in fact, crop stubble burning accounted for 42% of the city’s PM2.5 levels in the first week of November 2021. Ramesh looks in depth at this practice and how it links to agricultural water use.

The fields that are burned grow two crops per year, rice and wheat. Just the rice crop needs much more water than rainfall can provide, so groundwater is used to grow it. In the past farmers used to grow crops based on locally available water, then the green revolution expanded agricultural production, thanks in part to increased groundwater use. But groundwater depletion is an ongoing issue, and rice is a water-intensive crop. India is now the world’s largest consumer of groundwater, and aquifers are rapidly becoming depleted across the country.

India is now the world’s largest consumer of groundwater, and aquifers are rapidly becoming depleted across the country

Measures to conserve groundwater, however, have an effect on air pollution, found a study by Cornell University. In order to reduce groundwater withdrawals in the summer, farmers must transplant rice after a certain date, thus shrinking the time farmers have between the rice harvest and sowing winter wheat. Following the rice harvest, farmers have to quickly clear residues to prepare fields for planting wheat, and the quickest way is to burn them.

Possible solutions include advances in agronomy, for example, seeder devices to allow farmers to drill through crop residues and plant seeds with no need to burn stubble, and shorter-duration varieties of rice that may help with planting and harvesting timing.

Moreover, adaptation strategies proposed to conserve groundwater include switching from wells to irrigation canals that divert water from lakes and rivers. But researchers from the University of Michigan concluded that canal expansion will not fully compensate for the expected loss of groundwater in Indian agriculture, leading to a reduction in cropped acreage. Surface water is subject to rainfall variability, so a greater reliance on it would result in increased sensitivity to precipitation fluctuations, as well as any trends due to climate change.

Other options include switching to less water-intensive crops, and increased irrigation efficiency, such as through the adoption of sprinklers and drip irrigation.

Something is clear, there are complex relationships between food security and water availability, and sustainable water management involves multiple offshoots and trade-offs that need to be accounted for.

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