Only thanks to the handrails and safety nets in place were we able to traverse the 6 km long trail — known as the Torrent Neuf.
The 15th-century farmers and winemakers of the Rhône Valley who dared to build these overhanging irrigation canals had nothing but a spade, pickaxe and frayed ropes.
It was dangerous work that cost lives — but it saved a small region of Switzerland from near drought.
Switzerland might be called the “waterbox of Europe”, but a region in the southwest of the country, Valais, has historically suffered from aridity exacerbated by the foehn, a notoriously hot and dry wind found here.
Bordering Italy to the south and France to the west, the L-shaped region stretches from the mighty Matterhorn to Lake Geneva.
The alluvial soils of the lower slopes of the Valais are carpeted with fruit orchards, where around 70 varieties of apricots ripen in the region’s Mediterranean summers.
Meanwhile, in the alpine pastures of the German-speaking upper Valais, you can hear the bells of native animals, such as Valais Blacknose sheep and Herens cattle, in the shadow of the Alps.
These same peaks of more than 4,000 meters protect the vineyards planted in terraces (stepped cultivation technique) of the Valais, coloring the dramatic southeast-facing slopes of the Rhône Valley with green.
This is the heart of Switzerland’s fine wine industry, where endemic varieties such as Amigne and Goron de Bovernier have put Swiss vintages on the world map.
Despite being surrounded by some of the country’s wettest mountains, the sun-scorched, glacier-sculpted region receives just 500mm of rain a year, presenting a unique engineering challenge for irrigation.
Gravity-defying irrigation channels, known as bisses, are designed to divert glacial melt water from mountain streams to lower altitude pastures and vineyards.
To date, 200 of them, totaling 1,800 km in length, provide water for 80% of the irrigated area of Valais.
Measuring between 0.5 m and 2 m in width, the most primitive of the Valais bisses was carved out of rock. Others, like the 500-year-old Bisse des Sarrasins in the Sierre district of central Valais, have been dug out of tree trunks.
But the real engineering marvels were the “hanging channels,” designed to guide water from distant glaciers around canyons in the region’s wildest corners.
Located 1,200 m above the east bank of the River Morge in Savièse (a sub-region of Central Valais), the 15th-century Torrent Neuf suspended canals were built specifically to capture glacial milk before it fell into a gorge.
Using felled larches from the Foret du Ban du Torrent, workers created a series of three-sided wooden conduits that could protect against avalanches and falling rocks.
In a true tightrope performance, the men hung from the ends of the ropes, anchoring these overhanging channels to the limestone cliffs, with a double row of wooden beams called boutzets.
After watering the thirsty Savièse plateau for five centuries, the towering canals of Torrent Neuf were retired in 1935.
Responsible for spearheading the golden age of bisses in 1400 thanks to its success in irrigating wasteland, the Torrent Neuf canal was restored in 2013 as part of the cultural heritage.
In the lower valleys of the Valais, bisses were carved from earth.
Excavation debris reinforced the outer margins of the channel, as in the forest segment downstream of Torrent Neuf, known as Bisse de Ste Marguerite, fed by the Tsanfleuron glacier. Residents of Saviese, like Lydwine Bruchez, continue to get water from him.
The farmer raises horses, Herens cattle and a herd of 120 Suffolk sheep on her 60 hectares of land.
“Thanks to bisses, we [agricultores] we have fodder for our animals. It is a question of survival for agriculture in Valais,” says Bruchez.
“Water is life, as simple as that.”
The Valais, which stretches from Lake Geneva to the Matterhorn, is the driest region in the country — Photo: Sbosserty/Getty Images/BBC
On a hot, muggy May day, I watched in disbelief as Bruchez lifted a 5-kg iron plate (a family heirloom) into the air, before plunging it into a small channel of water that ran across its teeming field. of flowers.
The action — based on an ancient practice known as “zetti” — diverts water temporarily to flood farmers’ land through runoff.
Minutes earlier, Bruchez had raised the sluice of a small bisse located just 100 meters away to create the artificial water channel.
Typically, the only holders of the keys to these small manual gates are canal guards such as Philippe Emery, whose responsibilities include maintaining and cleaning the bisse, as well as coordinating its water distribution.
He has been the caretaker of the Bisse de Lentine de Savièse — located above the medieval capital of Valais, Sion — for 13 years.
Surrounded by a stone retaining wall, the Bisse de Lentine is 4 km long, bordered by a vineyard path, which runs along the north bank of the Rhône River.
The sight of a scorpion passing by is a clue to the semi-arid climate of Valais, where six species of cacti thrive, alongside figs and snakes.
“I found a 2 m long viper lurking here once,” says Emery, carefully crouching over the bisse to remove the metal plate that raises the water level.
Unlocking the hatch, he redirected the bisse water to a nearby 200 liter metal barrel.
Known as the ‘King of Bisses’, Bisse d’Ayent is honored on the 100 Swiss franc note — Photo: Van der Meer Rene/Alamy/BBC
These private and community “reservoirs” are where local producers draw water for their vineyards, usually starting in May when the rain subsides and continuing through September.
No plot of land is left unused by the region’s tireless winemakers, who have some of the steepest vineyards in the world.
The owner of the nearby Cave L’Orpailleur, Frédéric Dumoulin, takes care of land measuring just 1,000 m².
Unlikely sticking to 30-degree slopes, its Chardonnay vines grow to 900 m.
All 20 of Dumoulin’s grapes (including indigenous varieties such as Petite Arvine) are nurtured by Clavau — a bisse built in 1453 by the Bishop of Sion.
Thanks to its snow-capped alpine views and direct access to the guérites (wine bars), the Bisse de Clavau also serves as a popular hiking trail.
It is one of a series of mercifully flat bisses tours in the region that have proven to be a boon to regional tourism.
Starting in the village of St-Romain, the 5-mile Bisse de Clavau path winds through dizzying vineyards that descend to the Rhône River — a shimmering turquoise strip flanked by emerald-green slopes.
I followed the sound of the buzzing of bees and the bubbling of water that alternately flowed through the bisse’s open-air concrete channels, stone tunnels, and metal conduits.
One person who knows more than anyone else about the region’s ancient waterways is veteran Jean-Charles Bornet.
Raised in the folds of the sunny valley of Nendaz — home to the Valais’s largest network of bisses — the local councilor has fond memories of Bisse Vieux.
“I remember climbing up here when I was a boy with a huge picnic backpack that weighed more than me,” says Bornet, as we follow the contours of the canals under the shade of fir trees.
“It’s where I spent many weekends, and I still hang out.”
First documented in 1640, the 1,600 m high Bisse Vieux is the only one that transports water throughout the year from the Grand Désert glacier in the Alpes Peninos.
The 5 kg iron plate that Lydwine Bruchez uses to divert the flow of water is a family heirloom — Photo: Sarah Freeman/BBC
It is also a classic example of how this indigenous irrigation technology has been adapted to challenging terrain.
Halfway along its 7km course, the water cascades down a series of stepped metal chutes, which plunge 5m down a rocky ridge.
In a flatter section, Bornet points to the remains of a huge rock on the edge of the bisse, shattered by dynamite.
“This was the work of a local apricot farmer who happened to have a dynamite license,” he says, explaining that rocks that come loose from snow melt and natural debris such as twigs can often clog the bisse, demanding some kind of “explosive” intervention.
Traversing several river basins, longer bisses like the village of Saxon — 26 kilometers long — were an easy target for water robbers in the 14th century.
The solution? A water-powered warning hammer, raised by a paddle wheel at every turn, that still works today.
Bisses divert glacial melt water from mountain streams to pastures and vineyards at lower altitudes — Photo: Sarah Freeman/BBC
The guards spent the night in wooden cabins beside them, ready to pounce if the hammer fell silent, which could also indicate a blockage in the upriver bisse.
“Nowadays, a guard can tell just by the sound of the water if a rock is blocking some stretch along its course,” says Bornet, as he pulls a branch out of the bisse.
Although many Swiss outside the Valais have not heard of bisses, the 100 Swiss franc note is adorned with an illustration of one of the most spectacular: the Bisse d’Ayent.
Built in 1442, its passage of overhanging canals adjacent to a 1,800 m rocky ridge is an engineering feat that earned it the nickname “King of Bisses.”
“The bisses are the result of the ingenuity and audacity of the Valais and its people,” says Emilie Morard, head of the Valais European Markets Tourism Board.
“We are proud of this ancient knowledge.”