National Geographic on Ladakh (located between India and Pakistan):
In 2013 he noticed that ice, even at a low altitude and at the height of summer, stayed frozen in the shade of a bridge. He realized that he could help villages freeze water in winter for use in spring. Shading vast expanses of ice was impractical, but a tall mound would shade its own interior—and the steeper the sides, the better, because that reduces the area exposed to the sun. “High school math told me that a cone was the simple answer”
That first test stupa was 20 feet high, held 40,000 gallons of water, and lasted until May. Since then, Wangchuk has taught villagers around Ladakh to build stupas. In 2019 they made 12, two of which were more than 100 feet tall. This year they built 26, with nine cresting 100 feet.