Over the last few days, torrential rainfall has wreaked havoc in north India, particularly in parts of Himachal Pradesh, Punjab, Haryana, Delhi, and Chandigarh. It has triggered landslides and flash floods, leaving hundreds of people stranded. As of Monday, at least 22 related deaths were reported.
Map 1 | The map shows the amount of rainfall recorded in the 24-hour period ending at 8.30 a.m. on July 9, 2023.
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North India, where rainfall exceeded 200 mm, stands out. On the other hand, except for some parts of Gujarat and central India, the rest of the country received scant rainfall. While the map only depicts the rainfall for the latest day available, this trend holds true for most days of July.
Chart 2 | The chart shows the cumulative deviation from the usual rainfall recorded, on all days of July 2023, across meteorological subdivisions.
The graph shows, on any given day, the percentage change (increase/decrease) from the Long Period Average rainfall recorded cumulatively this monsoon. Each line corresponds to one of the 36 meteorological subdivisions. The subdivisions in north India, especially the areas in and around the places highlighted in Map 1, are given a distinct colour. India’s overall deviation is also highlighted.
As the chart shows, nearly all the meteorological subdivisions which recorded high increases from normal rainfall were in the north. Punjab led the list with an increase of over 200% from normal rainfall on all the days of July this year. In Himachal Pradesh, the increase from normal ranged from 85% to 110% on all the days of July. The increase from normal rainfall in Uttarakhand and Haryana surpassed even Himachal Pradesh’s deviation in the past four days, peaking at 115% and 113%, respectively, on July 10. Western Uttar Pradesh has also recorded a sudden increase in rainfall in the past few days — an 84% increase from normal on July 10. The grey lines, which show the deviation of non-northern subdivisions, are closer to or even lower than the zero-line, showing that rainfall was either on expected lines or was deficit in these regions. The only exception was western Madhya Pradesh, which also recorded rainfall that was much higher than usual.
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Notably, the deviation from normal rainfall for India on the whole, which had remained below zero on all days since the start of the monsoon this year, entered positive territory on July 9 for the first time. But it is important to note that many parts other than north India are still experiencing a monsoon deficit.
Chart 3 | The chart shows the actual rainfall recorded on a July day in millimetres across select north Indian cities. Each grey circle corresponds to a July day between 1952 and 2022. The highlighted crosses correspond to a July day in 2023.
On July 9, Chandigarh recorded a 24-hour rainfall of 283 mm. The second highest level of rainfall of 144 mm was recorded in Chandigarh on July 6, 1988. In fact, 283 mm is the highest-ever 24-hour rainfall for the city for any day since 1952. Kullu in Himachal Pradesh also recorded its wettest July day, and second-wettest day ever. With 51.8 mm rainfall on July 9, Delhi recorded its wettest July day since 2006.
In the last few days, at least 10 stations measuring the water level in rivers/tributaries spread across Himachal Pradesh and Uttarakhand recorded the highest flood level recorded in history. Rivers/tributaries in Giri, Bata, Meenus, Tons, Satluj and Ropa Khad in Himachal Pradesh, and Bhagirathi-I, Fica, Mandakini and Pinder in Uttarakhand either touched or surpassed their highest flood levels in the last few days.
Source: Indian Meteorological Department, IMD’s Yearly Gridded Rainfall Data, and the Centre for Monitoring Indian Economy
vignesh.r@thehindu.co.in
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