Is Cauvery Basin heading for another poor year?


It is almost exactly a year back on August 1st 2016 we published this post about how the Southwest Monsoon has been showing a dichotomy in terms of rainfall pattern with coastal Karnataka & Kerala getting a much more raw deal compared to the Konkan coasts of Maharashtra.  If one were to look at the sub division wise performance one can clearly see a pattern, Konkan & Goa along with rest of Maharashtra seeing near normal rainfall while Kerala, South Interior Karnataka, Coastal Karnataka all seeing less rainfall with S.Int Karnataka & Kerala seeing high deficits.

It is indeed very disheartening to see the storage levels of dams in Karnataka not very different from last year overall at the same time.  The worrying trend is despite a decent start to Monsoon in June and 1st fortnight of July except for Harangi the other three Cauvery Basin dams in Karnataka are showing levels which are lower than last year.

This poor performance in these areas is reflecting in how the Cauvery River Basin has been performing so far this year. It is a worrying read that Cauvery River Basin is seeing the highest deficit among all river basins in the country recording 38% lesser rains compared to long term average as of 4th August 2017.

Regular weather observers know that July & August are the critical months for this river and for that matter both Karnataka & Kerala in order to ensure a successful monsoon season.  With July seeing deficit rains will August change the fortunes, unfortunately if one were to look at the OLR maps which give an indication of how things could pan out in the immediate future, it does not look great with possibly suppressed phase of monsoon conditions likely to continue for the next couple of weeks at least with initial forecasts for September looking better.

The numbers that stack up are very clear, most of core monsoon zones in South India need rainfall in excess of 35% for the remaining period.  For these numbers to be achieved a poor August does not augur well if one looks at the normal rainfall pattern of September which contributes only between 10 to 20% of the seasonal monsoon rainfall.  For the sake of farmers & the governments in power we need monsoon to revive quickly.

But there is a  larger question one needs to find an answer “Is Monsoon dynamics over the southern parts of Peninsular India going through long term changes and should we consider Cauvery River Basin as a perennially deficit river?” 

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