This year, the Western Ghats along the Konkan coast in Maharashtra have seen record-breaking rainfall, followed by devastating floods and landslides.
In the first week of July, all the weather stations of the Indian Meteorological Department in the Konkan region had registered deficit rainfall, lower than the long-term average. By the end of the third week, however, all stations had seen excess rainfall: Mumbai Suburban recorded 251% of the long-term average, Ratnagiri 195%, and Thane 191%.
Many places along the Western Ghats saw extreme rainfall events. For instance, on July 22 and 23, Mahabaleshwar recorded 594 mm of rain. The previous high recorded in the hill station was 491 mm in 2008.
So far, 213 people have died in the Maharashtra floods. The highest number of deaths have taken place in Raigad district, where a landslide on July 22 killed 90 people in Taliye village. The district received 67% excess rainfall in the second week of July, which shot up to 138% in the third week, compared to the long-term average for the same period.
To understand the , Scroll.in spoke with KJ Ramesh, former Director General of the Indian Meteorological Department, and J Srinivasan, Distinguished Scientist at the Divecha Centre for Climate Change, Indian Institute of Science, Bangalore. Excerpts from the interviews:
What meteorological processes are behind the heavy rainfall in the Western Ghats?
KJ Ramesh: Since 2010, [global] warming has accelerated. The period between 2010 to 2020 is the warmest decade recorded in history globally. And warming has reached 1.2 degrees compared to the pre-industrial levels.
What this warming does is that it causes the atmosphere to hold more moisture than it used to hold earlier. And when the atmosphere holds more moisture, it will shell out that moisture somewhere. What this means is that regions which are traditionally heavy rainfall zones as well as those which are not can be expected to get heavy rainfall.
Now, traditionally also the Western Ghats and the North East India are heavy rainfall zones. We are seeing epochs of heavy rainfall events since 2018 along coastal Karnataka and Kerala: the Kerala floods in 2018, then floods in Coorg, and excess rainfall in Nasik and Marathwada region in 2018-’19. This year the phenomenon has extended to the Konkan coast.
J Srinivasan: In Western Ghats, most of the high rainfall occurs when moist air from the Arabian sea hits the mountains. If the winds are parallel to the mountain range you do not get much rain but when it is perpendicular to it we get heavy rain. Hence, the wind speed as well as direction is important. In Western Ghats, rainfall above 100 mm in a day occurs on a few days during every monsoon season – it is not unusual.
What could be the long-term impact of these heavy rainfall events on the fragile ecology of the Western Ghats?
KJ Ramesh: There are positive and negative sides to this. This will definitely increase the slope instability of the Ghats. Where mining activities happen, the slopes are destabilised by mining activity. Even roads and railway lines have an impact on slope stability. But there are technical solutions to this. You can identify the potential vulnerable areas of destabilisation and create structures to provide support to the slopes. And in areas where deforestation has happened in a big way, you have to undertake rapid afforestation.
On the positive side, if such excessive rainfall is happening for days in the river catchment area, then it will lead to accelerated rate of flow into the reservoirs, filling them quickly. Already in July, the Srisailam Project on Krishna river is full – this used to happen in August. This means that there will be more water availability for utilisation in activities like agriculture. But we have to build additional storage capacity.
The excess rainfall presents both opportunities and risks and this is especially true when all assessments of the Intergovernmental Panel on Climate Change estimate the monsoon rainfall will only increase, not decrease.
J Srinivasan: The Western Ghats ecosystem has evolved over thousands of years to tackle heavy rainfall. But, during the past hundred years, rapid deforestation, mining and road construction has upset the balance, and hence, there are landslides after heavy rainfall.
There need not be large-scale deforestation [to trigger landslides] – even if trees are removed from regions with high slopes, there will be landslides. Even in the current situation, if you look at the photographs of landslides in Taliye village in Raigad, you do not see many trees.
This year, apart from India, the Rhine valley in Western Germany, Henan district of China and New York also witnessed record breaking rainfall levels followed by floods. Are these events in India, Germany, China and the United States linked in any way?
J Srinivasan: What happened in Germany and China is different from what happened in India. The rainfall in Germany and China were truly extreme rainfall events. The rainfall in China was 200 mm per hour. Such heavy rainfall has not been seen before.
The destruction in China and Germany is mainly on account of heavy rainfall, while in Western Ghats, it is on account of land-use change.