The waterfall is the destination and it is not the point. The point is the three kilometres you walk to reach it, and specifically the fact that those three kilometres run along water in a reserve that has almost none.

Why Chinnar is dry

Everything a visitor associates with Idukki — the tea, the mist, the cold, rain that goes on for a fortnight — happens on the western flank of the Western Ghats, where the south-west monsoon hits the wall of the mountains and empties itself. Chinnar is behind the wall. It takes something on the order of five hundred millimetres of rain a year, spread across roughly forty-eight rain days, and most of that arrives with the north-east monsoon between October and December rather than with the monsoon that defines the rest of the district. Five hundred millimetres is less than a tenth of what falls on the coast on the other side of the same range.

The result is a landscape that does not look like Kerala. Thorn scrub and dry deciduous forest on red-brown ground, sandalwood in the folds, bare earth between the trees, star tortoises walking on it. You can leave a cardamom hill in the morning and be somewhere that looks like the Deccan by lunch, and the drive between them is under fifty kilometres.

And then there is the river

Running through all of that is a ribbon of tall, closed, properly wet-looking forest, a few dozen metres wide, following the water. Ecologists call it riverine or gallery forest; it exists because the trees there reach groundwater the rest of the reserve cannot. Standing on the route you can see both forests at once, touching, with maybe forty metres of horizontal distance between the thorn scrub and the closed canopy. There is no clearer demonstration of what a mountain range does to rainfall anywhere in Kerala, and you do not need to know any ecology to see it.

The animal that lives in it

Chinnar holds India’s principal population of the grizzled giant squirrel, Ratufa macroura — a large, shy animal named for the white-flecked grey of its coat and tail. It is a canopy species and it lives in the tall riverine trees along the Pambar and the Chinnar. It does not live on the dry hilltops. This matters practically, because two walks leave from the same counter at Alampetty and only one of them goes where the squirrel is: the culture trek climbs away from the water onto the tops, and Roampedia’s page for that walk says so plainly. If the squirrel is what you came for, this is the walk to book.

The corridor supports the rest of it too. Tufted grey langur and bonnet macaque have been photographed within about two hundred metres of the trailhead; a crested hawk-eagle at the same distance; a stream ruby damselfly, which is a river insect and could not be anywhere else, at three hundred and thirty metres. Chinnar’s lists run to roughly 225 birds, 52 reptiles, 28 mammals and 963 plants, across an altitude range from about 400 m on the river to 2,522 m at Kumarikkal — more than two kilometres of vertical inside one 90 km² reserve, which is the other reason the species lists are so long.

The rarity nobody expects

Chinnar also holds a small population of white gaur — Indian bison with the pigment largely absent. One was photographed here and described by the photographer as the first clear photographic evidence of a white gaur in seventy years. You will almost certainly not see one. It is worth knowing it is there.

Walk it slowly

The temptation on a three-hour walk with a waterfall at the end is to treat the middle as transit. Do the opposite. The cascade at the bottom is eighty-four feet of water on rock and it looks much like other waterfalls; the corridor is the thing you cannot see anywhere else in the state. Go early, keep quiet, and watch the canopy rather than the path. Your guide — from one of the eleven Muthuva and Hill Pulaya settlements inside the reserve — will find the squirrel long before you do, which is most of what you are paying for.