Mountain Water Supply to Two Billion People Could Change

-From American Scientific, By Walter Immerzeel

The nights are long inside a tent 5,300 meters above sea level at the snout of Nepal’s Yala Glacier. At 8:00 P.M., after a meal of Nepali dal bhat (lentils and rice), the 10 members of our expedition take refuge against the cold in sleeping bags inside the small tents that make up our temporary camp. Falling asleep is tough because the low oxygen concentration fools our bodies into increasing their heart rates. As a consequence, I spend many overnight hours listening to distant sounds of thundering avalanches and cracking ice, contemplating whether to leave the sleeping bag to pee outside and what not to forget the next day. As soon as the sun rises, the camp is bustling, and we are on our way up the steep glacier to install special instruments at 5,600 meters.

Our team, which includes colleagues from the International Center for Integrated Mountain Development in Nepal, has been conducting field expeditions biannually in this place, called the Langtang catchment, since 2012. We have erected automated weather stations at the base camp and at higher elevations that measure precipitation, snow depth, radiation, temperature, relative humidity and wind, making Langtang one of the best-monitored high-altitude catchments in Asia. We need to visit the stations every six months to maintain the instruments and to download their data; there is no cellular network to transmit readings automatically, and the mountains tend to block satellite signals. On the current ascent we will mount new sensors on a metal frame three meters high that we will drill into the ice. The sensors will measure sublimation—the phase transition of ice directly to water vapor—by sampling temperature and vapor 10 times a second.

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