Sixty miles east of Mount Kailash, a stream trickles down from the Chemay-ungdung mountain range. Known as the Tamchok or &lsquohorse river&rsquo in Western Tibet, this is the source of the mighty Brahmaputra. Changing names with an easy whimsy, the river becomes the Tsangpo as it surges east for more than a thousand miles across Tibet&rsquos vast plateau, till it hits the snow-capped Namche Barwar (7,765m). The mountain blocks its progress due east, making the river loop around its base and giving rise to the &lsquoBig Bend&rsquo, a 900 change in the river&rsquos course from where it hurtles down and disappears into the Po Tsangpo gorge, which, at 5,030m, is the deepest valley in the world. Defying exploration for centuries, it was not until the late 20th century that the Gorge was finally navigated. Reappearing on the Indian border, the Siang &mdash or the Upper Brahmaputra &mdash crosses the McMahon Line into India&rsquos equally remote East Siang district of Arunachal. The son of Brahma is by now a muscular torrent surging through the Canyon Gorge.
The river now descends through a district drenched in dense rainforest, where canyons sweep across the landscape and silvery beaches lie along the banks. Lurking between the smooth sail sections are turbulences where the water rushes forward to form gigantic waves that crash into frothy &lsquowhitewater&rsquo. Big 20ft waves on Grade IV rapids rage through vast sections, some up to 500m in length, making for some of the most massive whitewater in the world. To ride these oceanic waves is an experience without parallel.
Yet this monster classic of river rafting remains completely within the ambit of even amateur rafters &mdash seven of us greenhorns did it in November. Our eight days on the river were preceded by a gentle ferry ride on the Brahmaputra from Assam into Arunachal, a two-day drive through the Siang Valley&rsquos rainforests, dripping with tall tree ferns, wild bananas and bamboo alongside exotic ferns and orchids. The spectacular drive through these remote hills was a fitting prelude to the adventure on the river itself.
The exhilarating patches of whitewater serve to punctuate the placid flow of the Siang elsewhere. Over a week, we work our way through the Siang Valley, from rapids ranging from an easy Grade II to a challenging Grade IV. Before we attempt the biggies, our guides scout the rapids to decide which line will be best to take. We then go into attack mode, furiously paddling against the might of 20ft frontal and diagonal waves. The riverbanks offer lovely campsites in the form of silvery, sandy beaches, some upto 2km long. A swim in the water usually proves irresistible. After each day&rsquos hard paddling, we find beaches such as these to pitch camp for the night. Our beach parties begin with sundowners at an early 4pm around a raging bonfire &mdash very conducive to lengthy discussions about the day&rsquos conquests on the river.
A two-day run, taking all we need on our rafts, leads us into the amphitheatre of the Nigguing and Marmong Gorges. This is one of the most gorgeous sections of the expedition. In this 50km stretch, the river hums an altogether different tune &mdash a few Grade III romps are interspersed with sections where the river flows placidly between sheer rocky walls and waterfalls cascading into the river. The hemmed-in gorge throws up rocky overhangs, which form huge enclosures where the water sometimes finds its way into narrow caves.
A ferry ride on the river is an ideal way to begin and end the trip. With just the odd fishing boat and pockets of tribal villages along the banks, this is a gentle way to bid goodbye to the beautiful river.