Satellite-based data and models show that irrigation has contributed considerably to an increase in moist heat over the Indo-Gangetic Plain during the past four decades1.
Such an increase in moist heat creates a heat stress that could affect millions of people living in India, Pakistan and parts of Afghanistan, an international team of researchers has found.
The effects of moist-heat stress, they say, could have an adverse impact on agriculture, labour efficiency, mortality and public health.
Irrigation has been shown to alter near-surface temperature and humidity. However, its contribution to dry and moist-heat stress in India remains relatively unexplored.
Analysing a combination of satellite data and model-based simulations, scientists, including researchers from the Indian Institute of Technology in Gandhinagar, India, found that irrigation decreased land-surface temperature over the Indo-Gangetic Plain between 1982 and 2015.
During this period, the mean daily moist heat increased significantly across India but at a faster rate over the Indo-Gangetic Plain, with a decline in dry heat.
Excess moisture from plants on green roofs and in green urban areas can also increase the surface humidity, worsening the heat-stress conditions under a warmer climate, the researchers report.
The researchers estimate that the increased heat stress due to irrigation over the Indo-Gangetic Plain can affect about 37–46 million people in South Asia.
References
1. Mishra, V. et al. Moist heat stress extremes in India enhanced by irrigation. Nat. Geosci. 13, 722-728 (2020)
