Alarm bells over shifting rainfall pattern

This year saw the highest post-monsoon rainfall in 50 years

The post-monsoon rainfall from October through November across Karnataka this year was the highest in the last 50 years. This accentuated the growing concerns that the shifting monsoon patterns being witnessed in recent years is induced by climate change and, in turn, could have a bearing on agriculture and crop output.

Two years ago, there was a prolonged dry spell during the south west monsoon and the reservoirs in the State had only 4% of their gross storage capacity till the end of July. But between August 3 and 10, 2019, the State received 224 mm of rainfall and the departure from normal for the period was the highest for more than 120 years.

Since the last few years, the timely onset of south west monsoon in the first week of June is followed by a monsoon-break during July. But come August, and there is a downpour that neutralises the rainfall deficit in a span of a week, resulting in loss of life and widespread damage to property.

‘August rains’

Kodagu has been witnessing such a trend since the last few years and the local community have come to dread “August rains”, as it is termed colloquially. This year, the rainfall during the south west monsoon – from June through September – saw a deficit. But post-monsoon rains made up for the shortfall.

According to the Karnataka State Natural Disaster Monitoring Centre (KSNDMC), Karnataka received 332 mm of rainfall against a normal of 173 mm from October 1 to November 30h this year and the cumulative rainfall for the period was the highest in five decades.

Though the post-monsoon rains neutralised the shortfall for the period June through September and ensured that the reservoirs were full, they brought in heir wake crop damage and misery to farmers.

“All reports indicate a shift in the monsoon pattern and this may have an impact on the agricultural pattern in the long run,” according to N. Narendra Babu, Research Associate at the Agro Met Field Unit of Indian Meteorological Department at Naganahalli in Mysuru.

A team of scientists at KSNDMC who analysed the rainfall pattern and data from 1960 to 2017, published their findings in “Climate Change Scenario in Karnataka: A Detailed Parametric Assessment.” The scientists say that there is a shift in rainfall pattern over Karnataka and the quantum, intensity and distribution varies across the regions.

While the amount of annual rainfall and number of rainy days have increased in south interior Karnataka and Malnad regions, there is a reduction in the amount of rainfall in Kodagu, Kalaburagi, Yadgir, Dakshina Kannada and Uttara Kannada districts.

Drought and flood

The findings also indicate an increase in extreme weather events such as drought and flood. Across the State, there is an increase in annual rainfall in 39 taluks, pre-monsoon rains have increased in 28 taluks and north east monsoon rains have increased in 33 taluks.

The study indicates that areas with steady rainfall experience extreme precipitation events and regions are experiencing longer spells of little or no rainfall between two heavy rainfall events. Between 2001 and 2019 the State has experienced drought of various severity for 15 years, according to the KSNDMC study. In 2016, 139 out of 176 taluks in the State were drought-affected in the Kharif season and 162 taluks in the Rabi season. In 2018, about 100 taluks were drought affected in Kharif and 156 taluks in Rabi season, underlining the severity of the impact on agriculture.

The emerging evidence, according to the scientists, calls for measures to mitigate the impact of such extreme weather events on agriculture which otherwise, could have a bearing on food, nutritional and water security.

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