Sasthamcotta Lake

The story of Sasthamcotta Lake

Most of Kerala’s famous waters are backwaters — brackish lagoons where the sea and the rivers meet. Sasthamcotta is the great exception. It is pure freshwater, holding no common salts and supporting almost no floating plants, which gives its surface an unusually clear, glassy stillness. Ringed on nearly every side by steep little hills that fall into narrow valleys, and closed off to the south by a long earthen embankment (about 1.5 km) that holds the lake back from the paddy fields, the lake feels less like a Kerala backwater and more like a hill tarn that wandered down to the coastal plain.

Its surface spreads across roughly 373 hectares (about 920 acres), and it is deep by Kerala standards — an average of around 6.5 m and a maximum of about 15 m in places. That depth and volume are why it matters far beyond tourism: Sasthamcotta is the principal source of drinking water for the Kollam (Quilon) region, meeting the everyday needs of roughly half a million people. To sit on its bank is to look out over the supply of an entire city.

The lake takes its name from the shrine on its shoulder — the Sasthamcotta Sree Dharma Sastha Temple, an ancient Sastha (Ayyappa) temple that the lake wraps around on three sides. The place-name literally binds the deity to the lake, and the two have been thought of as a single sacred landscape for centuries. Pilgrims to the temple and day-trippers to the lake arrive in the same stream, so the shore mixes the hush of a protected wetland with the bustle of a working shrine.

The lake’s most-repeated wonder is its cleanliness, and the explanation attached to it is wrong. Guides, tourism notes and the official Ramsar information sheet all credit a larva called ‘cavaborus’ with eating the bacteria in it. No such creature exists; the word is a long-lived misspelling of Chaoborus, the phantom midge, whose larvae are predators of zooplankton rather than bacteria feeders. What is genuinely unusual here is duller and more interesting: it is soft, nearly free of common salts, low in nutrients and almost without rooted plants, in a basin fed by rain and groundwater rather than by a river carrying a catchment’s worth of silt and sewage. The clarity is a consequence of the lake’s hydrology, not of an insect.

It is also a living wetland, not just a reservoir. The lake and its wooded hills shelter freshwater fish (commonly cited at around 27 species), together with butterflies, dragonflies, wetland birds and shoreline greenery — the sort of quiet biodiversity that earned it international recognition. Small country boats and pedalos ply the near shore, and a lakeside walk under the trees, with the temple bell drifting across the surface, is the classic Sasthamcotta afternoon.

And then there are the monkeys. Resident troops live around the temple and along the bank, sometimes in large numbers, and are regarded by devotees as holy — a detail that turns an ordinary lakeside stroll into a slightly mischievous one. They are as much a part of the Sasthamcotta experience as the lake itself, and visitors are wise to guard their bags, snacks and spectacles accordingly.

Legend & myth

Temple tradition tells that Lord Rama, returning to Ayodhya after defeating Ravana, halted here and performed rituals by the lake. As he left, he is said to have deputed Neelan — the chief architect of his vanara (monkey) army — to remain and serve at the spot. The troops of monkeys that live around the temple today are, by this legend, descendants of Neelan, which is why they are treated as sacred. It is a story told as devotional legend rather than history — offered here as the temple’s own tradition, not as verified fact.

The Ramsar sheet is worth reading in full, because it disagrees with itself more than once. Item 7 says the lake supplies drinking water to half a million people; item 15, a few lines later, says nearly ten million — in a district whose entire population at the 2011 census was 2,635,375. Item 7 also notes, of a lake at nine degrees north and 33 m above sea level, that it does not get frozen in winter. Item 16 declares the lake totally devoid of any flora; item 18 credits it with 21 species of herrings and sardines of the family Clupeidae, a marine and estuarine group, against the 27 freshwater fish species claimed two pages earlier. None of this makes the designation wrong. It does mean the sheet is a 2002 compilation rather than a survey, and that numbers taken from it should be dated as such.

One more correction, and it is the one that matters at the shore. Every source calls this Kerala’s largest freshwater lake, and that is true — Vembanad is many times larger but brackish and open to the sea, which is exactly the distinction being drawn. What is not true is that the figure attached to it is current. 373 hectares is the area entered on the Ramsar sheet in 2002. Tourism copy still prints it, or 375, as though nothing had happened since. By December 2016 the press was reporting the lake drying; by May 2018 it was reported that nearly half of its 3.73 sq km had become dry, cracked ground, with the level falling at roughly 50 cm a year, and Wetlands International South Asia had warned that at prevailing extraction the system could dry out within a decade. When a brochure gives you 373 hectares, it is quoting a measurement older than most of the people reading it.

The purity story also has a date on which it publicly failed. In May 2018 the Kerala Water Authority stopped drawing drinking water from Sasthamkotta after complaints of discolouration, its assistant executive engineer reporting that the depleted water showed symptoms of the presence of iron bacteria in large quantities — water that stained faintly red and threw a precipitate on boiling. Supply to Kollam Corporation and neighbouring panchayats was switched to alternate-day pumping from the Kallada Irrigation Project canal, which could deliver under 15 million litres a day against a demand of 37.5. The lake celebrated worldwide for a bacteria-eating larva was taken out of service because of bacteria.

The monkeys themselves are better documented than the legend that explains them. Around sixty live at the Sree Dharma Sastha temple on the bank and are fed fruit in the morning and temple rice in the afternoon, with a full meal on plantain leaves on festival days, paid for out of a ten-lakh-rupee fixed deposit — five lakh given by a local working abroad, five from the temple committee. A second troop of roughly a hundred, made up of animals that left or were driven out of the temple group, lives around the market and is a genuine nuisance: crops eaten, kitchens raided, tanks broken, washing stolen. In 1999 residents went to court and the district court ordered 102 monkeys relocated to Kaanayar forest. The population recovered. Sacred and problematic are not alternatives here; they are the same animals.