Chennai is desperate for water and its residents continue to look up to the sky for rain. Weather experts note that the southwest monsoon has become more reliable in the past decade, but does not necessarily increase storage in waterbodies.
The Meteorological Department has forecast that there is a possibility of light rain in some parts of the city till Monday. But this will be preceded by sweltering day with the maximum temperature rising to 41 degree Celsius. On Saturday too, Chennai sizzled at 41.5 degree Celsius in Nungambakkam and 42.1 degree Celsius in Meenambakkam.
Chennai digging deeper for water
While there is a delay in the usual thunderstorm season in the city, weather experts note that the southwest (SW) monsoon has become more reliable than the northeast monsoon during the past decade. Rainfall picks up in Chennai only after mid-July.
Y.E.A. Raj, former deputy director general of meteorology, Chennai, said the city got an average rainfall of 45 cm during SW monsoon. Rains that come after a harsh summer would only prevent further decline in groundwater levels and not help improve the water table, he said.
In the past decade, 2011 was a good SW monsoon year, as Chennai received 85 cm of rainfall.
In recent years, Chennai has had a better SW monsoon, sometimes helping increase the volume of annual rainfall, despite a poor northeast monsoon.
For instance, Chennai received 53 cm of rainfall during SW monsoon in 2016. This was much more than the 33 cm that was received during NE monsoon. Rains between June and September pushed the annual rainfall to 106 cm during 2016, he said.
Indiscriminate groundwater extraction and unrelenting urban development are also reasons for severe water shortage, note weather experts. Monsoon has been favourable for several years and the volume of average rainfall cannot be changed according to growing demands, they add.
Weather blogger R. Pradeep John recalled that Chennai received a whopping 70 cm of rainfall in June 1996, leading to flooding. This is much higher than the normal rainfall of 8 cm recorded during June and was an exception.
“We often have only indirect benefits like inflows from Mettur to Veeranam tank and better groundwater recharge. We cannot expect SW monsoon rainfall to translate into storage in city reservoirs as rains will be sporadic,” he said.
Last year, while SW monsoon was near normal, the NE monsoon was poor. There was a possibility of rain in the city after June 20, he added.
Citing Cyclone Vayu for the sluggish progress of SW monsoon this year, Mahesh Palawat, vice-president, Meteorology and Climate Change, Skymet Weather Services said winds were diverted towards the cyclone and this had led to a prolonged dry weather.
Article source: https://www.thehindu.com/news/cities/chennai/southwest-monsoon-more-reliable-for-the-city-say-experts/article27952306.ece