The PWD of Tamil Nadu keeps a record of Observatory Wells in each district. A comparison of the current depth to August 2010 reveals interesting trends.
Let’s look at the absolute depths for the years 2010 and 2015 (bear in mind, the Y axis is depth in meters),
As is apparent, in 5 years, 27 of the 30 regions have shown an increase in depth. Or, depletion of ground water. The extent of depletion is uneven, but if we were to average it across the state, the depletion rate is 0.34 Meters per year!
The average rate of depletion, being as high as it is, still hides how bad the situation is. The depletion is uneven as one’d expect. But what’s shocking is that the Delta region of Kaveri, starting from Trichy downstream to Thanjavur and Thiruvarur have seen their ground water levels drop by 36.41%, 52.32% and 44% respectively. In just 5 years! Some other districts you’d suspect will have depleted their ground water, such as Salem, just shock you with the scale: 59%.
The district wise depletion in ground water in percentage terms over a 5 year period is,
Chennai, perhaps because the government made rain water harvesting mandatory, has not been as bad as some of the other places. Though, it’s still lost about 15% of its ground water in that period.
This is desertification of Tamil Nadu. There’s no other way to look at it. And this also means the delta districts will have to switch to something other than paddy as their primary crop as early as possible. Importing rice, surely, is cheaper. The state cannot afford a crop that requires standing water.
The impact of ground water depletion on soil fertility in the detla region and the impact of declining quality of water on health are aspects that require further study. Hopefully someone in the Tamil Nadu government or another research institution is doing that. Let’s hope that gets published and is accessible to lay readers.
Desalination on a massive scale within 5 years will be a necessity. Perhaps Madras’ brightest are better off working on these areas compared to adding another app to the sharing economy. Surely, this will have a large enough market for most VCs, even.