Overview of Indian Monsoon 2018 – Was it a “Normal” Monsoon?

The summer monsoons have retreated. In a detailed scientific analysis, the India Meteorological Department (IMD) concluded that 2018 monsoon season has led to over 9% less rainfall. And the distribution of the rainfall remained uneven throughout the country; some are facing drought while some places have suffered the loss of lives and vegetation in a furious flood. Let us see a compiled overview of Indian monsoon 2018.


In one of our May 2018 blogs, titled “Rainfall in India – Current Scenario, Prediction and Harvesting” we presented a predictive analysis by India Meteorological Department (IMD) which stated that Monsoon 2018 is going to be “normal”, making it a good year for the farmers. Now that the four-month-long southwest rainy period has ended, the numbers are out to see how close we are, to the predictions made earlier.

Overall, this monsoon, our country has recorded 9.4% rainfall deficient, making it a sixth monsoon drought of the century (following 2002, 2004, 2009, 2014 and 2015). The present statistics are contradicting the speculations made before the advent of the monsoon season. Here is the compilation of those statistics.

But before getting into percentages & numbers, here are some threshold values concerned with, what we call “normal” and “deficient” rainfall.

Understanding the Thresholds

The IMD categorises monsoon rainfall at a state or a district level, into the following segments:

  • Deficient” monsoon if it received 20-59% less rainfall, compared to the long-term average rainfall.
  • “Large deficient” if it received is 60-99% less rainfall.
  • “Deficient Monsoon” if the cumulative rainfall across the country remains -10% or above.

In India, the southwest monsoon accounts for 70% annual rainfall of the country. This means that the rainfall plays a highly crucial role in our agricultural economy, which is being valued at Rs.18 lakh crore or 11% of Gross Domestic Product (GDP).

Region-Wise Indian Monsoon 2018 Overview

This monsoon season has showed extreme deviation, as far as different regions of India are concerned- rain, drought, floods, all at once. Here is a summary of rainfall, in various states and regions of our country.

Northeast India

By 1st.September 2018, northeast India has experienced 24% shortfall of rains.

There were many low-pressure systems over the Bay of Bengal. Their movement was recorder westwards, moving across central India. Out of 10 low-pressure areas being formed during the season, one system intensified into a Cyclonic Storm, one into a Deep Depression and, four into Depressions.


Northern India

The day-to-day variability of rainfall has led to floods in the regions of Himachal Pradesh and Uttarakhand.

Southern India

23 out of total 30 districts of Karnataka state are declared to be hit by drought. 274 blocks in six districts of Andhra Pradesh are under “severe drought” conditions. On the contrary, Kerala has received 24% more rainfall than the normal threshold.

Western India

Jaisalmer and Barmer districts of Western Rajasthan get less than 60% of normal rains. The Marathwada and Vidarbha regions of Maharashtra have met with a drought-like situation.

 Northwest, Central India, and South Peninsula

These regions have been luckiest so far, and have received a well distributed satisfactory rainfall, with only a marginal deficiency of 2% in Northwest, 7% in Central and 2 percent in South Peninsular area.


The Changes in the Monsoon Trends

We can all feel that something is not right with the monsoons, from last many years. The researches have pointed out the reasons as well – the pollutants, global warming, et. al.

Kerala floods 2018 can be misleading. Too much rain that caused the dams’ overflow, happened because it rained heavily in a smaller span of time (24 hours). But it doesn’t mean that the overall rainfall was heavy.

A huge mismatched-trend is into action here. There are long dry spells between the heavy rainfalls. The heavy rainfall gets concentrated over a few days, making the overall rainfall season unaffected, rather rainfall deficient. The number says, in a 121-day southwest monsoon, an average 95% of monsoon rainfall occurs for only 3 to 27 days.

A Report by NASA’s Integrated Multi-satellite Retrievals for GPM (IMERG)

Global Precipitation Measurement (GPM) is a joint mission satellite by NASA and Japan Aerospace Exploration Agency (JAXA). It was built to estimate the rainfall around the world. NASA’s Goddard Space Flight Center in Greenbelt, Maryland through IMERG showed that a short period between 9 to 13 July 2018 witnessed the heavy rainfall along Arabian Sea Coast and large areas of north-central India. For instance, Mumbai was reported to have at least 525 mm (20.7 inches) of rain within this period.

This trending behaviour of Indian monsoon has other ill-effects. Based on the report published in the journal called Nature Communications, the scientists of IIT Kanpur imply that this uncertain nature of the monsoon is supporting the increase in suspended particles or aerosols, in the atmosphere. Though these aerosols are important in the formation of clouds, their too much quantity is interfering in timely formation of clouds, resulting in extreme rainfall patterns.


 Some Positivity

Even though the analysis of monsoon 2018 does not seem to be too impressive, few occurrences are still making people smile.

  • There is an increase of 2.6% in sowing of the Kharif crop, as compared to the last year.
  • There is also a 5% rise in water reservoir levels, compared to 10-year mean storages.
  • The rainfall has manifested a good soil moisture in the land, distributed across the country. This adequate soil moisture may help Rabi crops to grow well, during 2018-19.


A solution for preventing water deficit, by Chaitanya

This analysis of the rainfall in the current year 2018 reveals two things – overall rain fell below the expected normal amount and the shorter period of time has experienced heavy rainfall which caused floods. Rainwater harvesting and groundwater recharging, at individual levels or at a larger scale could be one of the solutions to harness the heavy rainfall, received in short time span.

We at Chaitanya make sure that you find every rainwater harvesting solution under one roof. Even though other factors are also needed to bring back the stability and even distribution of rainfall across India, RWH system can contribute its bit.

You can shop for RWH products such as rainwater drainage gutter, rooftop RWH filters, gravels and RCC Hume pipes for recharge structures.

Read our blogs to understand more about rainwater harvesting and call our expert team for the RWH survey at your premises.


Leave a Reply

Your email address will not be published. Required fields are marked *