guardian: Apocryphally, villagers in the 13th century “grew” such glaciers across mountain passes to stop the advance of Genghis Khan. by Michael Safi
'More than a decade ago, another Indian engineer devised an update. Chewang Norphel earned the nickname the “iceman of Ladakh” by using a network of pipes to divert meltwater into artificial lakes on shaded sides of the mountain. The water would freeze at night, creating glaciers that grew each day as new water flowed into the basin. Norphel created 11 reservoirs that supplied water to 10,000 people.
'“The problem was that it couldn’t be done in lower altitudes, where people actually live,” says [Sonam] Wangchuk. The lakes were also restricted to heavily shaded areas, and simply melted too quickly to make up for the shortfall in water wrought by increasing temperatures. Adapting the concept became Wangchuk’s obsession.
'“The ice needed to be shaded – but how?” he says. “We couldn’t have it under a bridge, or use reflectors, which aren’t practical at scale. So we thought of this conical shape: making ice shade itself.”
'The conical shape hit a sweet spot, maximizing the volume of ice that can be “grown”, while minimizing the surface area exposed to direct sunlight. That means it keeps melting well into the spring, releasing up to 5,000 litres of water each day by “storing it in the sky”, Wangchuk says.'