Lockdowns Cut South Asia Smog. They Could Fill Reservoirs, Too.

Cleaner skies over South Asia that resulted from pandemic lockdowns last year likely affected the timing of snowmelt in the Indus River basin of Pakistan and India, researchers reported on Monday. From a report: The lockdowns cut emissions of soot and other pollutants, as people drove less and the generation of electricity, largely from coal, was reduced. That meant less soot was deposited on snow, where it absorbs sunlight, emits heat and causes faster melting. The cleaner snow in 2020 reflected more sunlight and did not melt as fast, the researchers said. In all, that delayed runoff into the Indus River of more than than one and a half cubic miles of melt water, they calculated, similar to the volume of some of the largest reservoirs in the United States. More than 300 million people depend on the Indus for water, much of which starts as snow in the high peaks of the Karakoram and other mountain ranges.

Timing of melt water runoff in the spring and summer can be crucial for managing water supplies over time. In many parts of the world, climate change has affected this timing, with warmer temperatures and a shift to more rain and less snow causing more snow to melt sooner. Slower runoff can thus be beneficial, helping managers of reservoirs store more water and maintain a steady flow over the year. Ned Bair, a snow hydrologist at the University of California, Santa Barbara, and the lead researcher, said that while they could not prove conclusively that the pandemic was the reason for the timing delay, 'it seems unlikely that anything else would have led to that.' India imposed a nationwide lockdown in late March last year that continued through early May. Several studies showed rapid improvements in air quality in that period, particularly in and around Delhi, which is notorious for having some of the most unhealthy air in the world.

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