KOCHI: With the extreme mood swings of the monsoon bringing Kerala under the shadow of an impending drought, scientists are confused over the reasons over the sharp dip in rainfall this season. Though it has been nearly two months since the southwest monsoon set in, the state’s reservoirs have less than 20 per cent storage.
As on August 1, there was a 32 per cent deficit in rainfall with Idukki and Wayanad districts recording an alarming 50 per cent decline in rainfall.
“The situation is alarming as we get 70 per cent of the annual rainfall during the southwest monsoon. Only two months are left for the withdrawal of monsoon and if we don’t get continuous rainfall in the next two months, there will be a water crisis during the summer season. This year, there was a 55 per cent deficit in summer rainfall and the southwest monsoon also has failed to recharge the declining groundwater level,” said V P Dinesan, head, Geomatics Division, Centre for Water Resources Development and Management (CWRDM).
The winds that bring the monsoon clouds to the Kerala coast originate in the equatorial belt of the Indian Ocean. As it crosses the equator, the winds change direction and become westerly. Carrying the moisture from the Indian Ocean, the winds enter India through Kerala and advance to cover the subcontinent by the end of July.
However, according to scientists, change in the wind flow pattern and Cyclone Vayu have diverted the monsoon clouds to Central India. While Kerala received torrential rainfall in 2018, this time the rain gods have blessed Maharashtra. Cyclone Vayu, which developed in the Arabian Sea soon after the onset of monsoon, sucked the moisture from the air above the ocean and carried it northwards as it moved.
The monsoon entered a dry phase after Cyclone Vayu and the state witnessed an unusually dry spell in July. “The change in the weather pattern is unexplainable. The monsoon winds blow at a height of 1.5km over the surface. The winds blow at 90-degree angle to the surface while entering the subcontinent and cause widespread rainfall after hitting the Western Ghats.
However, this time winds are blowing at 45 degrees angle, which has led to flow of the monsoon clouds to Central India,” said K Satheesan, Assistant Professor at Cusat’s Department of Atmospheric Sciences. However, the Indian Meteorological Department is expecting good rains from August 4 onwards as depression is developing in the Bay of Bengal.
“Earlier we used to get continuous rainfall over a period of time which enabled deep percolation of water and recharge of groundwater resources. However, nowadays we are getting heavy rainfall over a short period. Excessive rain will lead to fast draining of water into the sea which limits groundwater recharge,” said S N Kumar of Department of Geology, University of Kerala.