Climate Change Increases Flood Risk in Peru

The rising danger of glacial lake flooding in a warmer climate has important implications for humans and animal populations in Peru’s Cordillera Blanca. A recent study in CATENA by Adam Emmer et al. examined a large swath of nearly 900 high altitude Peruvian lakes in the mountainous Cordillera Blanca region, studying their susceptibility to outburst floods in light of modern climate change.

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A variety of glacial lake sizes in the Cordillera Blanca (Source: Elizabeth Balgord).

An outburst flood occurs when the dam containing glacial meltwater, usually comprised of either glacial ice or a terminal moraine (glacial debris lying at the edge of the glacier), fails. Glaciologist Mauri Pelto commented in the American Geophysical newsletter that the moraine dams are “just comprised of gravel, sand and clay dumped by the glacier” and “high water levels caused by upstream floods, avalanches or landslides can cause failure,” leading to major damage of the landscape. The team’s research elucidated that the incidence of glacial lake outburst flooding (GLOF) is increasing and the general distribution of alpine lakes is shifting upward in the region as temperatures warm. 

Knowing a lake’s size, configuration and type allows local water management in the Cordillera Blanca to be improved, according to Emmer et al. By mapping lakes with the classification of either moraine-dammed or bedrock-dammed, the team’s analysis can help local hydrological experts improve water management techniques for the changing distribution of alpine water. It also contributes to the scientific community’s overall understanding of ongoing environmental change.

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A large, high elevation glacial lake lying before the high Andes (Source: Elizabeth Balgord).

By studying the Cordillera Blanca region’s alpine lakes through a combination of remote sensing (high resolution aerial imagery and measurements) and field observations, Emmer’s team categorized 882 lakes by their size and altitude, ultimately referencing their findings with historical data to observe water redistribution over the last 60 years. Emmer et al. established that glacial lakes had expanded in size and number at higher elevations and disappeared at lower elevations since the 1951 study by Juan Concha in the same region. This finding confirms that environmental change and glacier retreat are strongly correlated in the high alpine.

Results from the analyses showed that from 1948 to 2013, lakes that remained in already deglaciated areas tended to be resilient and generally maintained water levels throughout the 65-year examination. Moraine-dammed lakes in particular resisted disappearing despite glacial retreat, suggesting that bodies of water dammed by materials other than ice were more adaptable to recently warmer temperatures. 

The team also noticed that despite the recent resiliency of moraine dammed lakes, glacial lake outburst flooding was caused predominantly by these dams in the early portion of the Cordillera Blanca’s glacial retreat, in the 1940s and 1950s. Flooding in more recent years has occurred in bedrock-dammed lakes. Although glacial lakes were recorded to have shifted from 4250-4600m in the late 1940s to predominantly above 4600m today, no statistically significant trend was established relating outburst flooding to any particular elevation.

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A research team gathered at the waters edge (Source: Elizabeth Balgord).

In order to reduce the risk of flood damage in local communities, Emmer et al. suggested continuous monitoring of young, developing proglacial lakes, using extensive flood modeling and outburst susceptibility assessments to account for future changes in the glacier. Understanding that the melting of glaciers is accelerating in a warming world, the need for more intensive local efforts in response to the threat of flooding is apparent.  

The Peruvian government has responded to high lake levels in the mountains of the Cordillera Blanca by “building tunnels and concrete pipes through the [weakest] moraines to allow lake drainage to safe levels,” according to Pelto. The government then rebuilds the moraines over the drainage system to strengthen it. By incorporating the monitoring techniques suggested by Adam Emmer, the government has the opportunity to manage and stay ahead of the flood risk as temperatures continue to rise. 

Glacial lake outburst flooding is hardly unique to the Peruvian landscape. This December, the Kathmandu Post illuminated the growing danger of GLOFs as the Nepalese Dhaulagiri Glacier recedes, creating a hazardous environment in the Mt. Nilgiri region. Researchers at the Chinese Institute of Mountain Hazards and Environment also established a strong link in Tibet between rising temperatures and glacial melting, contributing to more frequent and larger glacial lakes than in the past 50 years. With the growing number of alpine lakes and increased temperatures, ice dams are highly fragile and prone to failure.

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A variety of landscapes exist at different elevations in the Peruvian Andes (Source: Elizabeth Balgord).

Emmer et al.’s study offers an interesting evolutionary perspective on the state of the Cordillera Blanca. The study’s publication illustrates that even the planet’s most dramatic, seemingly unchangeable environments are plastic under the force of global climate change. The redistribution of alpine glacial lakes across the world’s mountainous regions indicates that the risk of outburst flooding should not be taken lightly. The team’s suggestions for future monitoring, to either mitigate the flooding hazard in populated regions or coordinate adaptation efforts, further illustrates the gravity of the situation. Although the risk of outburst flooding has only been studied in specific locations, the changing state of glacial lakes is already quantifiable and may be an effective proxy for monitoring the future extent of global warming.

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Photo Friday: The Glacial Alaska Range

The Alaska Range is a narrow, 700-kilometer mountain range defined by rugged peaks and large U-shaped glacial valleys. The range lies in the southeast corridor of Alaska and is home to Denali, the tallest peak in North America. The Alaska range is part of the American Cordillera and possesses peaks only trumped by those in the Himalayas and Andes.

For many decades, the Alaska Range has played host to an incredible variety of landscapes and ecology, with visitors traveling from all over the world to hike, climb and sight see in Denali National Park. One-sixth of Denali National Park, or approximately one million acres, is covered by glaciers, which transport thousands of tons of ice each year, according to the National Park Service. Take a look at GlacierHub’s collection of images of Alaska’s impressive peaks and low valleys shaped by glacial activity over the past million years.

 

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An aerial view of the high altitude peaks of the Alaska Range (Source: Matt Verso/Creative Commons).

 

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Road entering Denali National Park on the east edge of the Alaska Range (Source: Arthur Chapman/Creative Commons).

 

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The U.S. Army flies a helicopter toward Kahiltna Glacier, the longest glacier in the Alaska Range (Source: Defense.gov/Creative Commons).

 

Moving toward the Harper Glacier in Denali National Park (Source: Mikep/Creative Commons).
Moving toward the Harper Glacier in Denali National Park (Source: Mikep/Creative Commons).

 

An aerial view of the Upper Muldrow Glacier, Denali National Park (Source: Pete Klosterman/Creative Commons).
An aerial view of the Upper Muldrow Glacier, Denali National Park (Source: Pete Klosterman/Creative Commons).

 

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Looking south across the Monahan Flat (Source: Albert Herring/Creative Commons).

 

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Looking east across the Monahan Flat (Source: Paxon Woelber/Creative Commons).

 

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Southern edge of the Alaska Range (Source: Denali National Park/Creative Commons).
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A Walk Up Jomolhari

A trip to Bhutan last month provided me with an opportunity to visit one of the glaciers in the country along the crest of the Himalayas. I had hoped for such a trip since I first visited Bhutan in 2011, since I was curious to learn what local people thought about glacier retreat, but I had not previously had the chance to travel above the middle-elevation regions. In October, though, my colleagues Ed Cook, Paul Krusic and I had received permits to enter the high country. We arranged for horses to carry our gear, and hiked in for two days to Jigme Dorji National Park. We set up our tent in the village of Soe, where we attended a mountain festival and met with local officials and residents. Ed and Paul spent several days to take samples in the old-growth forests close to the tree line; they drilled cores in the trees, which they would later analyze to reconstruct the climate history of the region.

I realized that this was an opportunity for me to take a day on my own and hike up to the glaciers. I kept an eye on the weather, since clouds had been building up every afternoon, sometimes bringing rain, and I did not want to be trapped in a storm high on a mountain. The national park officials warned me to be careful if I left the main trails; they had had difficulties in rescuing foreign tourists who had gotten lost, or who had slipped. They reminded me that Bhutan, unlike Nepal, did not have helicopters that could fly in to remote areas if an accident occurred.

A view of Jomolhari from above Jangothang. (source: Ben Orlove)
A view of Jomolhari from the trail. (source: Ben Orlove)

On the morning of Friday 9 October, the skies were a clear blue, offering the promise of good conditions for at least several hours. Moreover, I had an excellent guide. Renzin Dorji, the man whose horses we had chartered for two weeks and who had led us up the trail, had grown up in Soe. He had herded yaks as a boy and knew the countryside well.  At the age of 37, he was old enough to recall the mountain when the glaciers had been larger.

We set off from Soe and came to the valley that led up to Jomolhari. Its summit, 7326 meters in elevation, rose high up into the sky. We set off on the north side of the creek that flowed through the valley, ascending slowly on a trail that led through meadows. Seeing the dense groves of junipers and birches, I thought of Ed and Paul. Renzin and I slowly ascended to the first moraine—a line of boulders across the valley, which had been pushed downslope by the glaciers in earlier, colder periods when the ice masses on the mountain had advanced to lower elevations.

Yaks in a wetland at Haluphu below Jomolhari source: Ben Orlove
Yaks in a wetland at Haluphu below Jomolhari (source: Ben Orlove)

When we came over the lip of the moraine, we saw Haluphu, a broad flat area across which the creek meandered in broad curves. Sixty or seventy yaks were grazing on the pastures or standing the creek. Renzin explained that the herders had recently brought their animals down from the high summer pastures to these lower elevations (between 4000 and 4500 meters) where they would spend the winter. In a month or so, temperatures would fall below freezing, and the snows would arrive. But in early October, the temperatures, which seemed about 15 or 18° C, were so warm for the yaks, with their thick dark wool, that they would enter the creek to cool off.

The massive peak of Jomolhari loomed in front of us beyond the grass-covered slopes. I looked up at the mountain and asked Renzin about it. He recalled that the ice had reached much lower down when he was a boy. The warm summers of recent years were the reason for the shrinkage of the glaciers, he said; much more water came rushing off the glaciers than in the past. It would be very serious when all the ice was gone, he thought. In fact, life might end altogether in the area. But that would be far in the future, since there was still a great deal of ice left. And the streams were still full, the pastures still abundant. Local people cared about the mountain, he added. Every household sends at least one person to the large festivals to honor Jomolhari that are held at a temple in another valley that came off the mountain. A monk came from Lingzhi, a village a day’s walk away, to lead these festivals. Renzin seemed to suggest that the mountain did not feel neglected.

An abandoned firepit used by Cordyceps collectors. source: Ben Orlove
An abandoned hearth used by Cordyceps collectors. (source: Ben Orlove)

We walked down from the moraine to the side of the creek in Haluphu. Renzin pointed out signs of new economic activities. He indicated a crude fireplace, a sign that people had come in the late spring or early summer to collect a medicinal fungus, called Cordyceps, which they sell for very high prices, either in government auctions in Bhutan or to buyers a day’s walk away across the border in China. He also showed me a large pit where local people had come to dig sand which they would mix with cement for the construction of government buildings, shops and houses in Soe and other villages. Earlier in the last century, stone buildings, sometimes chinked with mud, had replaced the yak-hair tents of the more nomadic pastoralists, and now cement was becoming common. The Cordyceps and sand-collecting were linked: flush with income from sales of fungus, local residents were constructing larger houses than they had had before. Renzin pointed out a new risk as well: there were large rocks on the flat areas along the creek. Rockfalls from the sides of the valley, especially in summer months, are more common than they had been in the past—possibly a sign of melting permafrost at high elevation, I thought. Renzin mentioned that yak-herders remained in higher pastures during the period of rockfalls, though others, eager to obtain products that they could sell at high prices, came then to collect Cordyceps and sand.

Sandpit at Haluphu, below Jomolhari source: Ben Orlove
Sandpit at Haluphu, below Jomolhari (source: Ben Orlove)

There were a number of animal trails that led up beyond Haluphu. Renzin led us on one which took us to a second moraine, composed of larger boulders than the first. Beyond that was a lake, named Haluphu Tsho, with strings of prayer-flags stretched across the point at its base where the creek emerged. The waters of the lake were a pale green, filled with fine glacier sediment. We saw a few yaks here as well, fewer than below.

Exposed rock and dark ice on lower slopes of Jomolhari. Moraine in foreground. source: Ben Orlove
Exposed rock and dark ice on lower slopes of Jomolhari. Moraine in foreground. (source: Ben Orlove)

The trail continued on above the lake to a third moraine. Here, at an elevation of about 4750 meters, the boulders were larger still, and had sharper edges. We stopped to look closely at Jomolhari, its immense mass filling the broad space at the head of the valley. The upper sections of the mountain were white with snow, but lower down the last winter’s snows had melted, revealing ice that was quite dark, almost slate gray in color. Was this local dust, or soot that had blown in from the diesel vehicles and wood fires of India? It would be possible to trace the history of this dark ice by taking cores, and seeing what particles were contained in the older ice, below the surfaces. Perhaps I would return some day with a glaciologist for such work, I thought. I recalled as well the warnings of the national park officials. The climbing had become difficult, and I did not want to risk a fall if I clambered over these large boulders to try to reach the ice. Moreover, this ice was further from the moraine than it had once been, since the glacier’s edge had moved upslope, revealing bare rock. The growing cloud masses on the summit removed any impulse to continue further: I did not wish to risk being caught in a storm higher on the mountain.

Renzin Dorji, with Jomolhari in the background source: Ben Orlove
Renzin Dorji, with Jomolhari in the background (source: Ben Orlove)

We sat in silence, staring at the mountain. After a while, I reached into my backpack and retrieved some snacks—Power Bars, a favorite of Ed’s and Paul’s, which we had both taken a liking to. We shared them, and then started our walk back. I reflected on the mountain and on the changes that Renzin had seen in the decades since he herded yaks in Haluphu as a boy. Renzin himself was taking part, in a small way, in the growth of tourism, by renting his horses to trekkers. The sale of medicinal fungi and of sand, the possibilities of trade (nearly all clandestine) with the growing towns just over the border in China: these new sources of income for local villagers were growing, perhaps as fast or faster than the glaciers were retreating. The final demise of the glaciers lay far in the future, while the trajectory of the new economy was uncertain. In the meantime, some features of earlier decades remained. Renzin’s wife and son cared for their yaks during the months when he accompanied foreign visitors, and their family sent a member to the festivals at the temple.

Blue sheep and yaks above Jangothang. source: Ben Orlove
Blue sheep and yaks above Jangothang. (source: Ben Orlove)

As we crossed the pastures below the first moraine, Renzin signaled to me to stop. He pointed out, just below us, a herd of blue sheep—a wild species, quite shy and rarely seen close up. Several yaks were grazing in their midst. I was pleased by this unexpected mix of the wild and the domesticated, at a spot not far from the villages in the main valley below Jomolhari. The presence of these animals gave me hope that the mix of old and new forms of human life high in the mountains might continue well into the future.

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Photo Friday: Glacial Moraine Maps as Art

Joerg Schaefer, a geoscience researcher at the Lamont-Doherty Earth Observatory at Columbia University, specializes in tracing the history of moraines through cosmogenic radionuclide dating. He depicts the results of his research in maps of moraines–the accumulation of glacial till and sediment at the end, or snout, of a glacier, or along its sides. While scientific in nature, the maps themselves are visually stunning- prompting GlacierHub to showcase some of the glacial maps from Schaefer’s research.

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Joerg Schaefer, photo from personal website

Schaefer is most interested in studying the dynamics of earth surface processes and their interaction with climate, as well as ice ages and the dating and quantifying of changes in earth’s climate and landscape. He can be contacted here.

 

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