Saline water intrusion threat looms large in Kerala

While climate change, rising sea levels play a meagre role, the main cause is the unscientific management of regulators and bunds
Meenachilar at Peroor
Meenachilar at PeroorPhoto | Express

KOCHI: Last week, the Kerala Water Authority stopped pumping water from Thazhathangadi, disrupting the supply of water to the panchayats of Kumarakom and Thiruvarppu in Kottayam district, after the salinity in the Meenachil river increased beyond the prescribed levels.

When the Thanneermukkam bund in Kuttanad was opened, there were no temporary shutters at Thazhathangadi, leading to an inflow of salt water near the Thazhathangadi pump house, the KWA said.

Meenachilar at Peroor
Along Kerala's coastline, rising salinity means daily water struggle

Meanwhile, in Kochi, saltwater is frequently entering freshwater areas like Chellanam, rendering water unusable and forcing local residents to depend on water supplied by tankers.

These are not isolated incidents. According to experts, this phenomenon of saline water intrusion into Kerala’s rivers will increase in the coming years unless immediate steps are taken. While climate change and rising sea levels play only a meagre role, the main cause is the unscientific management of our regulators and bunds, they pointed out.

“Many of the riverbeds in the state are below sea level. In fact, many riverbeds are lying in the minus territory because of the sand mining from our rivers over the past 40-50 years,” said C G Madhusoodhanan, hydrologist and CEO of Kochi-based Equinoct, a non-profit organisation providing science-based solutions to address the impact of climate change.

“Right now, our midlands are secure because there are regulators downstream to stop the ingress of salt water,” he added.

Thanneermukkom bund
Thanneermukkom bund

According to Madhusoodhanan, many people are under the impression that riverbeds have risen following the 2018 flood, leading to the accumulation of silt. There have also been instances of more dredging in the riverbeds after the flood.

“But the fact remains that what we have dredged over the past 40 years is the deposits of millions of years. Over all those years, several floods have come and gone. The mining that we have carried out cannot be filled with just one flood,” he said.

Several decades back, regulators were constructed in the state mostly to control the intrusion of saline water. Bijoy Nandan, dean, faculty of marine sciences, Cusat, said it is time to revisit these regulators as most of them are in ruins or in a dilapidated state. While the Thottappally spillway-cum-regulator was constructed in 1955 to prevent saline water entering Kuttanad, the Thanneermukkom bund -- built as part of the Kuttanad Development Scheme in 1974 -- was then considered the largest mud regulator in the country. It has since been reconstructed.

“While our regulators were constructed as a salinity barrier, no proper maintenance and regulation are done there, and they aren’t managed scientifically either. It is not only affecting the geo-chemistry but the fauna and flora too. During summer, salinity becomes high,”said Nandan, adding that salinity is prevalent in most of the rivers in the state.

According to Nandan, the Vembanad regulator, the oldest regulator in the state, is in a dilapidated state.

“The larger role of Thanneermukkam bund has not been defined yet,” he said.

Madhusoodhanan pointed out that if something happens to the shutters or the regulators, all the rivers will be filled with saline water the next day, and the water pumped from the rivers to all the drinking water projects will contain salt water.

“The water supplied to the irrigation schemes will also contain salt water, causing huge losses to the agriculture sector,” he said.

This has happened several times in the past, albeit in a small manner. “But the severity of the problem becomes heightened in the low-lying areas as the water requirement in the midlands rises,” he said. In 2017, about 2,800 hectares of paddy in the coastal areas of Alappuzha were damaged after saline water seeped into the fields.

Experts say..

  • The phenomenon of saline water intrusion into Kerala’s rivers will increase in the coming years unless immediate steps are taken

  • Regulators should be revisited as most of them are now in ruins or in a dilapidated state. While the Thottappally spillway-cum-regulator was constructed in 1955, the Thanneermukkom bund was built in 1974

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