EXPLAINED: The Monsoon effect and its overwhelming impact


Monsoon, the annual weather phenomenon which has a deep tryst with the vast swathes of India, has made its onset in Kerala on Wednesday.

Its four-month sojourn accounts for 80 per cent of the country's rainfall. Crucial for farming and replenishing the reservoirs and the groundwater table, Monsoon is also a key driver of the economy.

Farming accounts for nearly 15 per cent of India's economy and sustains more than half of India's 1.3 billion people. The southwest monsoon irrigates over 50 per cent of India’s farmlands.

The southwest monsoon had already made a splash in Andaman and Nicobar Islands, the India Meteorological Department (IMD) informed on May 21.

Initially, the southwest monsoon makes its landing on the south Andaman Sea and winds advance north-westwards across the Bay of Bengal.

Kerala rain

A good monsoon is instrumental in ensuring a good yield of some key kharif, or summer crops, like rice, pulses and oilseeds. Kharif crops, which account for 50 per cent of India's food output, are planted taking into account the arrival of monsoon rains in June.

In a normal monsoon season, farm output goes up, boosting demand for consumer goods as well as rural incomes. All of this leads to a robust economic outlook.

A poor monsoon season can lead to drought, supply issues and even accelerate food inflation. It can have a ripple effect on India's economy and growth.


Onset of Monsoon

According to the IMD, there are three major factors that determine the onset of monsoon.

The primary one is if, after May 10, 60 per cent of the fourteen weather stations along the southwest coast in Kerala and Karnataka report rainfall of 2.5 millimetres or more for two consecutive days.


Southwest monsoon normally graces Kerala around June 1.

The monsoon advances northwards, usually in surges, and covers the entire country by July 15.

Technicalities like the intensity of wind and the northernmost limit up to which the rain has advanced on a given day are the other factors taken into account.

Normal monsoon


The IMD foresees a normal monsoon this year. The Long Period Average (LPA), or the average of the season's rainfall across the country from 1961-2010, is forecast to be 98 per cent this time with an error margin of plus and minus 5 per cent.

The LPA is 88 centimetres.

Rainfall in Odisha, Jharkhand, eastern Uttar Pradesh and Assam is likely to be below normal. The rest of the country will have normal or above-normal monsoon, the IMD said.

Kerala braces for the worst


Having battled floods in 2018 and 2019, the Kerala government has laid out specific plans, keeping the COVID-19 situation in mind, to tackle the expected heavy rains.

The 2018 flood was one of the worst floods in Kerala in nearly a century. Over 483 people died and 140 were reported missing. About a million people were evacuated. The 2019 flood was equally severe with a death toll of 121.

According to the Kerala government, one-sixth of the total population of the state was directly affected by the two floods and related incidents.

The Kerala government has also initiated precautionary measures to avoid the overflowing of dams that may trigger floods during the monsoon.

In a directive issued to the Kerala State Electricity Board (KSEB) and Department of Irrigation, the government ordered the authorities to maintain water levels in major dams scientifically based on the rule curve.


The rule curve, or rule level, specifies the empty space to be maintained in a reservoir during different periods of the year.

Most dams in Kerala are under the jurisdiction of the Kerala State Electricity Board or the Irrigation Department.

A review of the water levels in dams would be carried out at regular intervals.

This year, the state is already battling the Covid-19 pandemic, which is peaking. It has asked concerned departments to be ready to tackle the situation in the event of floods.

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