Why is the Cauvery such a recurring flashpoint between Karnataka and Tamil Nadu?

In recent days, an array of hypotheses have been advanced to help answer that question.

Some of these are broad in their scope – tracing the long history of the conflict. Others focus on the here and now – rainfall patterns and reservoir levels this year.

Yet others have taken a more sociological look – which is how we ended up with diagnoses that include political grandstanding, Kannadiga nationalism, the role of the media, and more.

In the process, however, some ecological questions have not received the attention they deserve.

The Cauvery river originates in Karnataka and then flows through Tamil Nadu, before joining the Bay of Bengal. The two have been sharing its waters since the 19th century. But both states are more stressed for water today than ever before.

Water-tight situation

Take Tamil Nadu. In the last 20-odd years, the state has seen a sharp reduction in freshwater availability. For instance, groundwater levels are falling steeply.

Evidence of this can be found across the state. Travelling along the Noyyal, a small river that flows past Coimbatore and Tirupur before merging into the Cauvery, this reporter came across instances where groundwater levels were as low as 1,000 feet. Ten years ago, villagers said, they used to find water at 600 feet. And 20 years ago, they just had to dig 200 feet.

This is the story in large parts of the state. According to Tamil Nadu’s Water Supply and Drainage Board, as many as 142 of the state's 385 blocks are over-exploited – they are drawing out more water than is replenished in the year. Another 90 are moving in the same direction – classified as “critical” (33) or “semi-critical” (57).

The state is also seeing a depletion in two other major sources of freshwater.

Smaller rivers in the state – like the Noyyal – are carrying less water (and flowing fewer months each year) than before. As this story on Scroll.in tracing the river's decline reported, the reasons for this include illegal diversion of water for industry, falling groundwater levels and rising urban and industrial demands for water.

The last major source of freshwater in Tamil Nadu is the monsoon. The state gets about 20% of its annual rains from the Southwest monsoon from July to September, the bulk 70% comes later in the year, during the Northeast monsoon, which begins in December. But in the last 20-25 years, the southwest monsoon has largely failed.

Put all this together and what you have is a state in the midst of a water crisis. As the Water Supply and Drainage Board website says, the state has an annual shortfall of more than 300 thousand million cubic feet each year.

This gap between demand and supply is something that Tamil Nadu has in common with Karnataka and Kerala – the third state through which the Cauvery flows. In their submissions to the Cauvery Water Disputes Tribunal, set up in 1990 to look into sharing the river’s water, Kerala pegged its eventual demand from the Cauvery at 208.7 TMC and Karnataka at 410 TMC. Tamil Nadu asked for 641.5 TMC.

Adventures in unsustainability

This was a zero-sum game – the Cauvery did not have that much water to begin with. This showed in the tribunal's final order – it pegged water availability in the river at 740 TMC, and gave 30 TMC to Kerala, 270 TMC to Karnataka, 419 TMC to Tamil Nadu, 7 TMC to Pondicherry, and earmarked a grand total of 14 TMC for ecosystem services, for the river to perform its other ecological functions.

Embedded in the order, incidentally, is one reason why we will see more tussles over water-sharing like the one playing out right now.

The tribunal arrived at the 740 TMC figure based on old river flow data – from 1900-01 till 1971-72. The catch is, rainfall patterns as well as the behaviour of tributaries have changed enormously since then.

We see this in the Noyyal. And we see this further upstream in Karnataka, where other tributaries of the Cauvery, like the Arkavathy, are drying up sooner and sooner each year. As a result, less water is coursing through the Cauvery.

At the same time, other processes are chipping away at these rivers. In Tamil Nadu, rivers like the Noyyal are as good as dead because of pollution (see this and this). Other rivers, even the mighty Cauvery, are tottering due to rampant sand mining. Such is the scale that farmers in the state say the river will be dead in ten years.

That is the central paradox – if Tamil Nadu and Karnataka are slugging it out because of the water shortage, would they not also crack down on unregulated groundwater extraction, pollution and rampant sand mining?

But, as Scroll.in Ear To The Ground project reported from Tamil Nadu, that is not how things work. In response to its worsening groundwater crisis, the state actually withdrew its groundwater management act, which aimed to protect groundwater, prevent over-exploitation and ensure its planned development, saying its implementation would “have caused a public outcry”. Pollution and sand mining – both of which further reduce the quantum of freshwater – continue apace as well.

Instead, we get these attempts to shift public anger over dwindling water supply by blaming the neighbouring state – be it upriver or downriver.