All 20 of Dumoulin’s grapes (including indigenous varietals like Petite Arvine) are nourished by Clavau – a bisse built in 1453 by the Bishop of Sion. Thanks to its snow-capped Alpine views and direct access to guérites (wine bars), the Bisse de Clavau doubles as a well-trodden hiking trail. It’s one of a raft of mercifully flat bisse walks in the region that have proven a boon for regional tourism.
Starting at the village of St-Romain, Bisse de Clavau’s 8km-long path weaves through vertiginous vineyards that tumble down to the Rhone River – a ribbon of shimmering turquoise flanked by emerald-green slopes. I followed the sound of droning bees and babbling water that flowed alternately through the bisse’s open-air concrete channels, stone tunnels and metal conduits.
One person who knows more about the region’s ancient watercourses than most is bisse veteran Jean-Charles Bornet. Raised in the folds of Nendaz’s sun-drenched valley – home to the Valais’ largest network of bisses – the local councillor’s happy place is Bisse Vieux. “I remember hiking up here as a boy with a huge picnic rucksack that weighed more than me,” Bornet remarked as we followed the bisse’s contours beneath towering spruce trees. “It’s where I spent many a weekend, and still do.
First written about in 1640, 1,600m-high Bisse Vieux is unique in conveying water year-round, tapped from the Pennine Alps Grand Désert Glacier. It’s also a textbook example of how this indigenous irrigation technology was adapted for challenging terrain. Midway along its 7km course, water cascades down a series of stepped metal troughs, which plunge 5m to navigate a rocky ridge. On a flatter stretch, Bornet gestured to the remains of a huge boulder resting on the bisse’s bank, shattered by dynamite. “This was a job for a local apricot farmer who happens to have a dynamite license,” he said, explaining that rocks unstuck by melting snow and natural debris like branches can often obstruct the bisse, requiring some “explosive” intervention.
Crossing several watersheds, longer bisses like the 26km one in the village of Saxon were an easy target for water thieves in the 1300s. The solution? A water-driven warning hammer lifted by a paddle wheel at every turn, which still works today. Guards would overnight in wooden cabins alongside them, ready to pounce if the hammer went mute, which could also signal a blockage in the bisse upstream.