India's monsoon rainfall deficit at 14%: When does it become a drought?

The IMD said that with the onset of the southwest monsoon, India's overall rainfall deficit fell to 14 per cent on July 9, down from 30 per cent on June 30

The southwest monsoon finally covered the entire India on July 9, after first making landfall over the Kerala coast on June 4. The India Meteorological Department (IMD) said that the southwest monsoon arrived one day later than scheduled and warned of a significant reduction in rainfall activity over central India, including Maharashtra, Gujarat, and Madhya Pradesh, from July 9 onwards, and over south peninsular India from July 10.

 

The IMD also said that with the onset of the southwest monsoon, India’s overall rainfall deficit has fallen to 14 per cent on July 9, down from 30 per cent on June 30.

 

 

But what difference does a drop from 30 per cent to 14 per cent actually make? Does a deficit at that level mean India is headed for a drought? Here's how IMD classifies rainfall and when a deficit actually becomes a meteorological drought.

 

What does a 14% rainfall deficit mean?

 

According to the IMD, a rainfall deficit happens when the cumulative rainfall received over a given period is lower than the Long Period Average (LPA), or the historical average rainfall for that period.

 

LPA, which acts as a benchmark for forecasting, means the rainfall recorded over a particular region for a given interval, averaged over a long period, like 30 years, 50 years, etc.

 

India is witnessing a 14 per cent rainfall deficit, which means the country has received 14 per cent less rainfall than the LPA during the southwest monsoon season so far.

 

Between June 1 and July 9 this year, India received only 205 mm against the country’s LPA of 233.1 mm, marking a deficit of 14 per cent, according to multiple media reports.

 

According to IMD’s classification, a 14 per cent deficit still falls under the 'normal' rainfall category, as cumulative rainfall between 19 per cent below and 19 per cent above the LPA is considered normal.

 

When does a rainfall deficit become a drought?

 

To understand when a rainfall deficit becomes a drought, we must look broadly at the IMD’s classification. See the chart below:

 

Departure from LPA	IMD classification
20% and above	Excess
-19% to +19%	Normal
-20% to -59%	Deficient
-60% or lower	Scanty/Large deficient

 

According to the IMD, a meteorological drought is declared when the seasonal rainfall received over an area falls below 75 per cent of its LPA. It is further classified as a moderate drought if the rainfall deficit is between 26 and 50 per cent, and a severe drought if the deficit exceeds 50 per cent of the normal rainfall.

 

When is an entire year called a drought year?

 

A meteorological drought alone does not make an entire year a drought year. According to the IMD, two conditions must be met for a year to be classified as an All-India drought year.

 

First, the seasonal southwest monsoon rainfall for the country as a whole must be at least 10 per cent below the LPA. Second, 20-40 per cent of the country's geographical area must be under moderate or severe meteorological drought.

 

If more than 40 per cent of the country's area is affected by moderate or severe meteorological drought, the year is classified as an All-India Severe Drought Year.

 

This means that a 10 per cent or higher all-India rainfall deficit does not automatically make it a drought year. The classification also depends on how widely meteorological drought is spread across the country, making it a measure of both rainfall deficiency and its geographical extent.

 

While these are the IMD's meteorological classifications, official drought declarations are made by state governments, which also consider factors such as soil moisture, crop conditions, vegetation indices, and reservoir levels while determining relief and compensation.

 

How does meteorological drought differ from other types of drought?

 

According to the IMD, drought is the consequence of a natural reduction in precipitation over an extended period, usually a season or longer. Climatic factors such as high temperatures, strong winds, and low relative humidity can further aggravate the severity of drought.

 

Drought is broadly classified into four categories: meteorological, hydrological, agricultural, and socio-economic.

 

A hydrological drought occurs when stream flows, reservoir levels, or groundwater supplies become inadequate to meet established water needs. Meanwhile, an agricultural drought starts when soil moisture becomes insufficient for healthy crop growth, causing crop stress and wilting.

 

A socio-economic drought is the final stage, when prolonged water shortages begin to affect livelihoods and the wider economy, leading to problems such as unemployment, migration and food insecurity.