Mount Hualcan, about 20,000 feet above sea level. Image by Dan Grossman. Peru, 2011.

I’m traveling the world in search of the human face of the impacts of climate change. I encountered a sobering example yesterday, in Carhuaz, Peru. There, I met Juana, a middle-aged woman dressed in a white embroidered shirt, orange skirt and a grey felt hat. One Sunday morning in April 2010 Juana puttered around the rustic house she rented by a stream on the outskirts of Carhuaz, at the base of Peru’s Cordillera Blanca range. The day, like every Sunday in Carhuaz [pronounced car-WHAS], a bustling town of 60,000, was market day. But Juana herself was still indoors, planning the day ahead. There was work to do, including caring for the animals: her ducks, chickens and pigs.

At around 8:00, the house began to shake. Juana rushed out the rough-hewn wooden door and climbed to higher ground. Her adobe hut had been built within a few yards of the stream where, normally, a gentle current had swirled around rounded boulders. On this day the creek had become a wild torrent, not just of water, but of tree trunks and boulders—huge boulders, some taller than her daughter. As Juana told me her story in her native Quechua, through an interpreter, tears poured from her eyes. She said that as she watched from above, the flood took all her possessions, including her prized farm animals. Now she lives in a former stable. She makes a meager living washing clothes. Sometimes neighbors offer her gifts of a few potatoes or other crops they grow.

César Portocarrero told me the flood should never have happened, but that it could happen again. Portocarrero, a glaciologist and civil engineer, works for Peru’s National Water Agency, which, among other things, oversees public works to prevent floods. About two decades ago ago Portocarrero himself oversaw construction of a drainage tunnel that was designed to protect Carhuaz from such floods. He blasted the drain in stone just below the summit of Mount Haulcan [pronounced waal-KAHN], a 20,000-foot-high peak that glistens above Carhuaz. He had determined that a lake there, known as Laguna 513, posed a threat to the town. He had worried that if a piece of the glacier fell into the lake, a tsunami-like wave could have broken over the lake’s bank, creating a destructive flood of water and debris. In 1970, the entire town of nearby Yunguay, including 80,000 inhabitants, had been buried by just such a flood. The drain that Portocarrero built was designed to keep Laguna 513 at a constant level, about 60 feet below its banks. Thus, the basin became like a huge bathtub large enough so even the most ample bather couldn’t splash the floor.

Portocarrero says when he built the Laguna 513 drain he calculated that its basin would keep almost any imaginable icefall contained. But as Peru’s glaciers have retreated, the frequency and size of ice avalanches has increased. The April 2010 flood was caused when a 15 million cubic foot chunk of ice broke off the summit, tearing additional ice and rock as it tumbled. By the time it had reached Laguna 513 the volume had doubled. The basin was big enough to fit the debris without overflowing; still the force of the fast-moving icefall created a splash so big that a wave washed completely over lake’s 60-foot containment banks. The water that escaped raced down the course of the normally quiescent outflow stream, ripping up boulders and trees and everything else it overtook.

Portocarrero estimates that due to global warming his drainage tunnel now only protects Carhuaz against about 80 percent of Hualcan’s icefalls. Fortunately, the 2010 flood stayed contained in the banks of the stream, taking no lives and causing little economic damage other than to Juana. Of Janua he says, sadly, she probably broke the law by living too close to the stream. On the other hand a more powerful flood could happen any time, with much more severe results. A larger icefall could create a flood that would leap over the river’s banks, and cause much more damage or even loss of life. His agency has produced a feasibility study with several proposals for how to defend the town better. But so far, says Portocarerro, discouraged, there is no budget to build anything.

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Planet Earth's average temperature has risen about one degree Fahrenheit in the last fifty years. By the end of this century it will be several degrees higher, according to the latest climate research. But global warming is doing more than simply making things a little warmer. 

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