A kilometre downstream from the park boundary, at Pathrakkadavu, rocks bear painted marks denoting the point where the river would be dammed, the resulting reservoir flooding the forest around. The Kerala State Electricity Board (KSEB) plans a 64.5m high, 275m long, 70-megawatt (MW) dam project across the Kunthi in the near future.

Kunthi (named after the matriarch of the Indian epic, Mahabharata) is a drinking water source for downstream villages and tribal hamlets and a key tributary of Bharathapuzha (Nila), Kerala's second-longest river.

In the early 1980s, the central government scrapped a power project across the Kunthi river after India's first successful anti-dam campaign. The 89 sq km area of the Silent Valley was then declared as a national park. In the last 20 years, constant efforts have been made to conserve the park.

Kerala's environmentalists - including several writers and artistes - are aghast at the recent decision to build a dam in the southwest zone of the park. "Madness," says Mustafa Desamangalam, a filmmaker. They insist that the state government is reintroducing a smaller version of the old dam.

The forests of the Silent Valley - christened so because of a perceived absence of cicadas (tropical insect with a loud, chirpy sound) - are home to rare mammals, birds, reptiles and fish. They are also home to a variety of creepers, ferns and orchids. Some say the valley got its name from Macaca Silenus - the scientific name of the lion-tailed macaque, a medium-sized monkey found in the valley.

"The forests have a number of species that are found only in India and Sri Lanka," says Professor Madhav Gadgil, a famous environmental scientist at the Indian Institute of Science, Bangalore.

"There are over 180 kinds of birds here," says V S Vijayan of the Salim Ali Centre for Ornithology and Nature History, Anakkatty. He led the first environmental study of Silent Valley when a dam was planned here in the 1970s. "This is one of the two places on earth where the lion-tailed macaque can live."

Environmentalists note that to protect the biodiversity in the core of Silent Valley, there should be forests all around as a buffer, and the new project would breach this buffer zone. Besides, the forests are 'carbon sinks' in the sense that they absorb excess carbon dioxide (from fossil fuel burning) that blankets the earth and warms it up. Scientists say deforestation in the tropics may account for one-tenth to one-fifth of the carbon released into atmosphere by human activity during the 1990s.

"Soon after the 1972 UN Conference on Human Environment in Stockholm, Kerala (with its anti-dam struggle) gave the world hope. But after the Rio and Johannesburg (international UN) conferences we are back to square one," Dr B Ekbal, a neurosurgeon who served as vice-chancellor of Kerala University till recently. "The plan to build the dam is like turning the clock back."

The local people came to know that the state government was secretly planning a dam on Kunthi river during a public hearing in March 2004. Ever since, the environment vs development battle has been raging in Kerala.

The state claims that crippling power shortages have forced it to take this decision. "We are duty-bound to explore new possibilities," says Chandramohan, the KSEB chief engineer who studied the feasibility of the project. KSEB says the state's electricity demand is envisaged to double in six years as India's 16th Power Survey notes.

The Environmental Resource and Research Centre (ERRC), a private  consultancy group in Thiruvananthapuram (state capital), has done a rapid environmental assessment for the project. ERRC calls it a 'run-of-the-river' venture, a tag that denotes small and green dams. ERRC was commissioned to do the assessment by KSEB.

But environmentalists argue that the Rs 2,470 million (1US$=Rs 46) dam with  its 4.1 hectare reservoir and 7.4 km approach road may look rather innocuous on paper, as it was made out to be in the ERRC report, but be ominous in reality.

S Sathis Chandran Nair, a noted environmental scientist based in Thiruvanathapuram, questions the narrow vision of seeing the Silent Valley as an 'artificial administrative unit' of a notified national park that encompasses just about 89 sq km reserve forest area. "The actual biodiversity-rich natural landscape unit is larger than the reserved  forest, a contiguous forest tract along the south-western slopes of Nilgiris," says Nair. "This is a segment of the Western Ghats extending across many ridges and valleys, including the valley of the Kunthi and the plateau."

The protection of biodiversity demands preserving the largest possible  natural habitat unit, including the Silent Valley. "Protecting it is ensured by safeguarding an adequately deep buffer zone all around it," says Nair. The buffer zone includes part of the rich rainforest area, some plantations and land now encroached by villagers for farming.

Huge forest tracts in the buffer area are already threatened by loggers, settlers and cannabis cultivators. "Building a road in this inaccessible forest will amount to opening up the forest to these vested interests," says Tony Thomas, a local farmer.

The greens also argue that the Kunthi is a rarity among dozen-odd tributaries that feed the Nila. As Sugathakumari, the famous Kerala poet who was at the forefront of the 1970s campaign, puts it: "In summer, the Nila lies as if she were dead. There is a single live artery on her breast - that is the Kunthipuzha (Kunthi)."

A study by the River Research Centre (RRC), Chalakkudy (Trissur district), has noted that some of the main tributaries of the Nila dry up even in the rainy season because of upstream dams. "Even during this year's severe drought, the Kunthi had water in it," the study noted.

The ERRC research claims that the project would divert the river only to a 2.75 km stretch of uninhabited area. "The impact of a river's degradation affects the people living on its banks," says A Latha, an RRC scientist. "Besides, this is highland: the water that goes into the earth here contributes to water flow far away."

"The river is a drinking water source for several villages clusters and tribal hamlets," said Sunder Raj, a local activist. "It is state-sponsored robbery of resources." The heads of 12 panchayats (village councils), out of 16, recently held a meeting to protest against the dam.

Finally, the board's claim of generating cheap electricity from the Rs 2,470 million dam is also under criticism. The RRC study notes the figure calculated at the 1999 rate will be far higher, and by spending a fraction of the cost, the board could cut down its huge transmission losses.

Meanwhile, the local people recall an ominous quote in an old signboard at the national park: "The distance from Silent Valley (rainforests) to attapadi (barren hills) is covered by an axe."