Tamil Nadu’s Precarious Position

Tamil Nadu is a water deficit state. The state government acknowledges this and its own report on the extent of deficit and its impact on depleting ground water is a scary read. The  state’s water demand exceeds its known sources by 16%. If TN had a UP like population growth, it’s unimaginable what the water situation might have been. If you consider the state as an entity and compare it to that other state which is in the news for serious drought, California, Tamil Nadu is actually worse off. It’s worse off both seasonally and on a long term civilizational basis. Except water scarcity in Tamil Nadu is not the subject of obsessive focus for news outlets unlike in the Golden State.

The simple truth is: Tamil Nadu will deplete its already perilous ground water even if the rainfall is normal, given its current demand estimate. This makes “normal” a bare necessity. Now let’s look at the past two months of rainfall. The Indian Meteorological Department classifies the rainfall as normal since it’s only 5% below estimate. But that hides the real problem: the 5% deficiency is an aggregate across the state. The networks of water conservation don’t normalize water distribution like the Met Office aggregates the entire state’s data.

The deviation from the norm, if measured by each region, looks thus,

TN Rainfall


What’s striking is that the excess rainfall in just Coimbatore and Theni, both with greater than 100% excess rainfall, have had an outsized effect on the statewide aggregation. The Met Department’s own threshold of excess rainfall, greater than 20% the estimated norm, has been achieved in only 5 of the 34 regions. While 15 of them have less than 20% the estimated rainfall and are thus deficient by that yardstick. More significantly, 24 of the 34 regions have had lower rainfall than the normal.

We know that Least Mean Squared Error is a bad measure. But what this hides is so worrying. The three regions with the lowest estimated normal, Toothukudi, Ramanathapuram and Tiruppur, all have lower than the normal actual rainfall. By -29%, -42% and -13% respectively. Making the most water scarce region get worse. These regions will without a doubt overdraw their already depleted ground water.

The real question is two fold: why isn’t this on the front pages of every newspaper and why isn’t the only alternative – desalination plants – being pushed more aggressively? The cost of depleting ground water isn’t merely the absence of water; it’s also loss of soil fertility. Surely, the cost of all that when added up, makes desalination plants all across Tamil Nadu’s coastline an imperative. If Narendra Modi’s tilt to Israel has any benefit at all, let it be their expertise in desalination being brought to Tamil Nadu; not just to California.

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