Can we gain from changing rains?

India is undergoing a major transition with changes in rainfall patterns leading to increased frequency of droughts, floods, heat waves amidst fear of a major water crisis in the years to come. Why are these threats increasing? Head of Indian Meteorological Department’s (IMD) Climate Application and User Interface Group, Dr Pulak Guhathakurta, speaks to India Water Portal on what the current research on rainfall shows and what can be done to cope with these changes.

Why do you think it is important to study the rainfall in India?

The average annual rainfall patterns over different parts of the country show that it ranges from less than 13 cm over Ramgarh in western Rajasthan to 984 cm in Mawsynram in Meghalaya. The rainfall pattern also influences the climate of the country which varies from humid northeast (with 180 days rainfall in a year) to arid Rajasthan (with less than 20 days rainfall in a year). Even the mean rainfall patterns for the country as a whole are variable with the mean monthly rainfall during July (289.2 mm) being highest, contributing about 24.4 percent of annual rainfall (1187.6 mm). The mean rainfall during August contributes about 22 percent of annual rainfall while that during June and September contribute 13.8 percent and 14.6 percent to the annual rainfall, respectively. 

Rainfall in India is currently undergoing further changes due to climate change, leading to increasing instances of floods, droughts, making it important to study the trends in rainfall patterns to design better coping strategies for the future. Also, the Indian economy is still dependent on agriculture and the SW monsoon. Droughts and famines can prove to be lethal for the country.

How are rainfall patterns changing? What are the trends seen? Are there any region wise variations?

A decreasing trend in rainfall during the south-west monsoon is seen in 10 subdivisions namely Chhattisgarh, Jharkhand, Uttarakhand, Himachal Pradesh, Arunachal Pradesh, NMMT (Nagaland, Manipur, Mizoram and Tripura), sub-Himalayan West Bengal, Kerala, east Uttar Pradesh and east Madhya Pradesh. Eight subdivisions that include Madhya Maharashtra, Saurashtra and Kutch, south interior Karnataka, coastal Karnataka, Konkan and Goa, coastal Andhra Pradesh, Lakshadweep and Gangetic West Bengal show increasing trends.

Has there been a rise in extreme events?

Heat waves are increasing in the north, northwest, central, east India and northeast peninsula during hot weather season (April-May-June). Similarly, during cold weather season (December–January–February), northern parts of the country including Jammu and Kashmir are experiencing cold waves. Studies also show that there has been a noticeable increase or decrease in frequency of heat or cold wave days during the El Nino or La Nina events.

Analysis of tropical cyclones and monsoon depressions based on data from 1901–2010 shows that the frequency of cyclones is increasing during the post-monsoon season (October–December). Studies also show that there has been a significant decline in cloud cover which is responsible for a good monsoon in most parts of the country leading to a loss of one rainy day during the study period. This decrease in cloud cover is seen in the central and the west coast of the country while an increase in cloud cover is seen over the Indo-Gangetic plains. The high rate of urbanisation and growing particulate pollution in the central and west coast of the country could be one of the reasons for this decline in cloud cover.

What do studies reveal about the frequency of droughts in India, specifically Maharashtra?

Droughts in India

The intensity of droughts is also increasing. The area affected by drought is showing an alarming increase in states like Uttar Pradesh, Uttarakhand, Jharkhand, Chhattisgarh, Kerala, Assam and Meghalaya and Tripura. Many districts of states like Tamil Nadu, Odisha, east Madhya Pradesh, Himachal Pradesh, Punjab, Haryana, Bihar, Vidarbha, Marathwada in Maharashtra, north interior Karnataka, Tamil Nadu and sub-Himalayan West Bengal are also showing worrying trends with a significant increase in drought-affected areas. Drought occurrences have also been found to be high in most of the southern districts of Tamil Nadu during the northeast monsoon. The ENSO has found to have a signi?cant role to play in the meteorological drought occurrences over the Indian region.

Droughts in Maharashtra

Rainfall activity is thus getting more and more confined to the monsoon months, which will not fare well for agricultural activities in non-monsoon months and result in less groundwater recharge. This will also impact pre-monsoon temperatures leading to very high summer temperatures and consequent soil-moisture loss. Mean summer temperatures are already rising in most parts of Maharashtra.

Why are these changes happening? Are these inevitable?

What do you think needs to be done to cope with these changes?

With so much rainfall over short spans of time, we must focus on harvesting and storing as much water as possible and catching the rainwater where it falls besides making efforts at saving our environment by preventing deforestation, focusing on reforestation, identifying and protecting groundwater recharge areas, saving and making judicious use of available water resources.