CHENNAI: Believe it or not, among the major cities in the southern Indian peninsula, Chennai has the ‘dismal’ number of automatic rain gauges (ARGs) and automatic weather stations (AWSs) that relay rainfall information on a real-time basis.
For four river basins, Adyar, Cooum, Kosasthalaiyar and Kovalam, which put together form a gigantic Chennai river basin spread across 4,000 sq km, there are only 17 ARGs/AWSs. In contrast, the Bengaluru urban district, measuring 2,190 sq km has 82 ARGs and even a smaller place like Hyderabad has 26.
What does this mean? When an extreme weather event like that December 2015 or even Thursday’s evening spell, wherein the DGP office (Marina-Mylapore) received as much as 300 mm of rainfall in a span of just a few hours, Chennaites will be caught unawares in the absence of ‘live’ data.
An automatic rain gauge shows the intensity of spell and quantum of rainfall received every 15 minutes, which allows people to stay away from harm’s way and helps disaster management authorities take appropriate action.
Take Mumbai. It witnessed humongous flooding on July 26, 2005 due to 944-mm rainfall in a day. Over 60% of Mumbai was inundated to various degrees. At that time, there was no reliable real-time rainfall forecast mechanism and the IMD was unable to issue advance warnings due to lack of the state-of-the-art equipment. Post-2005, the Municipal Corporation of Greater Mumbai (MCGM) set up a network of 35 weather stations with tipping bucket rain gauges along with Indian Institute of Technology-Bombay within a year.
Currently, the MCGM has a network of 60 rain gauges. Most of them are installed on the roof of the fire station control rooms. These rain gauges have been programmed to give rainfall intensity in real time (every 15 minutes) to the emergency control room in the MCGM headquarters. The rain gauges also have a console capable of giving an audible alarm if the preset rainfall intensity exceeds 10 mm in 15 minutes.
So what did the Indian Meteorological Department (IMD) or Tamil Nadu government did after the 2015 Chennai floods on that front? Answer: Nothing.
When contacted, Kanduri Jayaram Ramesh, Director General of Meteorology, IMD, New Delhi acknowledged that it was a problem. However, he put the blame on the Tamil Nadu government for the shortcoming. “The State governments of Karnataka, Maharastra, and Telangana have put up a good network of ARGs, which should be emulated by the Tamil Nadu government,” he said.
The IMD is sending data on heavy precipitation and potential pockets where heavy rainfall is expected, using Doppler weather radars, to the Chennai Corporation, but more ARGs are needed to know what is happening on the ground and validate the forecast. “Actually, the Union Agriculture Ministry is in discussion with the Tamil Nadu government to set up more ARGs/AWSs and the high-power committee has listed out the specifications. I will raise the issue at the next review meeting,” IMD chief said.
Ramesh said a good network of ARGs/AWSs will enable monitoring of rainfall in real time and benefit disaster managers for mobilising rescue and relief.