Cauvery faces manifold threats in Tamil Nadu

The delta is up against a subsidence threat due to lack of sediment flow from upstream and seawater ingress

By S Janakarajan
Published: Wednesday 07 August 2019
All the major tributaries of the Cauvery in Tamil Nadu are heavily polluted due to the discharge of industrial effluent. Photo: Getty Images

The Cauvery delta is heavily stressed. Its contribution to the food security of Tamil Nadu and to the nation is critical. But admittedly, irrigation in the delta area is extremely inefficient, facilities for it are poorly maintained, and therefore, productivity per unit of water used is low.

Climate variability and the resulting changing monsoon conditions and extreme coastal events have a cumulative impact on farmers in the delta area. These have endangered fresh and brackish water resources, coastal freshwater aquifers, land and soil, rivers and streams, mangroves and human settlements.

Use of groundwater as an alternate source of irrigation is increasing in the delta area. In the entire Nagappattinam district and a substantial part of Tiruvarur and parts of Thanjavur districts in Tamil Nadu, groundwater has turned completely saline due to severe seawater ingress.

The irrepressible inter-state water dispute has increased risks and uncertainties. At the worst affected Nagappattinam, a district at the tail end of Tamil Nadu, it takes weeks or even a month to get water.

The short-duration kuruvai crop, grown from June to September, has steeply declined. Cracking clay soil in most areas here inhibits farmers from shifting to other crops. Therefore, the main crop is still paddy, contributing to over 30 per cent of rice production in the state.

Dairy as a secondary occupation is almost disappearing in the delta districts. Cattle population has registered a steep decline in the past few decades.

The delta districts have witnessed a drastic decline in goat and sheep breeding, and poultry, which provide an alternative source of livelihood. This means the degree of delta farmers’ dependence on agriculture is higher than in other districts in Tamil Nadu.

The ramifications of pollution, both from industries and municipal waste, are now more severe. All the major tributaries of the Cauvery in Tamil Nadu such as Bhavani, Noyyal, Amaravathi and Kodaganaru are heavily polluted due to the discharge of industrial effluent.

The towns located along the river dump domestic sewage into the river. Sand mining on the riverbed goes on ruthlessly destroying the riverbed, riverbed filtration and riverbed aquifers.

The delta is facing subsidence threat due to lack of sediment flow from the upstream as well as due to seawater ingress, increasing coastal flooding and coastal erosion. The entire Nagappattinam district is facing the threat of submergence due to global warming induced sea-level rise and ongoing coastal erosion.

(The author is a retired professor at the Madras Institute of Development Studies)

(This article was first published in Down To Earth's print edition dated August 1-15, 2019)

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