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The Supreme Court’s decision to reduce Tamil Nadu’s share of the water of Cauvery River is likely to lead to further groundwater depletion, coastal instability and salinity intrusion in the delta

The Grand Anicut dam across the Cauvery River in Thanjavur district of Tamil Nadu (Photo by Premnath Thirumalaisamy)

The Supreme Court has reduced the water quota of Tamil Nadu from the inter-state Cauvery River, citing data that suggested that around 20 TMC (thousand million cubic feet) of groundwater was available in the state and users in the delta can also fall back to groundwater. However, this delta is now “plagued with the issues of surface and ground water depletion, coastal instability and salinity intrusion”, says a recent report by Public Affairs Centre, a Bengaluru-based think tank.

The Cauvery delta is spread over 1.45 million hectares, 11% of the area of Tamil Nadu. It is a zone with a complex water system. The average annual rainfall is 945 mm, of which 48% is dependent on the north-east monsoon, and 32% on the south-west monsoon.

With the Cauvery dispute having gone on for decades, the delta is almost totally reliant on rain for recharging its water resources. So, monsoon failures lead to acute water scarcity and severe drought. The Cauvery delta has seen three consecutive droughts from 2011 to 2013.

This is in consonance with the forecast of Intergovernmental Panel on Climate Change (IPCC) that droughts, floods and storms will increase in severity and frequency, as the earth’s atmosphere gets warmer. In the winter between 2017 and 2018, the north-east monsoon rainfall has also been scanty thereby raising the fear of drought stalking the delta again.

Farmers facing hardship

Apart from this, there have been floods in 2010 and an increase in the intensity of cyclones in the past decade. The erratic behaviour of the monsoons has made farmers highly dependent on groundwater and the overdrawing of groundwater has worsened seawater ingress into the aquifers.

With agriculture being the primary livelihood in the region, such salinization of the primary water source has forced migration out of the delta. Farmers who chose to live on in the delta are unsure of when to sow their crops, as the May-September south-west monsoon has reduced in intensity and frequency, while the north-east monsoon is often delayed by 20-30 days.


Still, there is plenty of groundwater and therefore farmers have moved from two to three crops per year. While that has improved their incomes in the short term, soil quality has been affected adversely, the Public Affairs Centre study found. In turn, this has reduced productivity of crops. Add to this sand mining and extensive use of chemical fertilisers, and the ecosystem is no longer able to support as many people as it did before.

The researchers conducting the study also gathered the perception of residents about the changing rainfall pattern in 1984, 2004 and 2014. In Oorudayanatham village, they were told that in 1984, there had been a hot summer from April to the middle of June, the north-east monsoon rainfall was distributed between September and October, and it was misty from December to February.

In 2004, the summer stretched to the end of June, the north-east monsoon was from October to December with almost continuous rainfall in November. The winter was from December to mid-March.

In 2014, it was a very hot summer from March to July, the groundwater level plummeted and there was hardly any sea breeze and only three to four rainy days in May or June — a new phenomenon in the region. The north-east monsoon was delayed, there were only four to five rainy days till December and then there were “unseasonal” cyclones and low-pressure days between January and May.

The researchers heard of similar changes from residents of Valapuram, Sathangudi, Nandhivanam, and Karuvalarcheri villages in the delta. Their experiences are confirmed by the measurements of maximum and minimum temperatures in the region over the years made by the India Meteorological Department (IMD).

Government schemes inadequate

The state and central governments are aware of this problem and have a number of schemes meant to help farmers. The researchers from the Public Affairs Centre asked residents about these schemes. They were told that the schemes were not sufficiently tuned to the needs of the changing climate and that the schemes were not reaching the smallholder farmers who needed them most, especially the farmers from Scheduled Castes.

The researchers found that while farmers were aware of the changing rainfall patterns and had therefore moved to irrigation with groundwater, they were unaware of the link between the rainfall uncertainty and climate change, though such uncertainties were likely to increase due to climate change.

The Cauvery delta once had an extensive canal system. Now, they are largely defunct, choked up with silt and also encroached and unlikely to have more water after the Supreme Court judgement. So, over-exploitation of groundwater is quite likely to continue and worsen the situation, the study warns. Wells have already been deepened from 15 feet to 20 feet below the ground, even to 22 feet in some villages in search of a steady supply of groundwater.

This article has been abstracted from the research paper titled Can Farmers Adapt to Climate Change.


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