Men on the mountain

Men on the mountain

Melting glaciers in the Andes

04/2018  | Reading time: 15 minutes

Although the South American subcontinent is one of the most water-rich places of Earth, some of its parts might encounter serious water scarcity in the future. Beyond topographical and atmospheric particularities, this is also due to the fact that glaciers, showing signs of increasing recession as a result of the increasingly warm atmosphere, play an important role in many places’ water supply. What nobody really sees now is how local people will react to the changing circumstances, and what social processes will be magnified by this phenomenon.

At first glance, one might find that the southern half of the American continent, otherwise beset by many other troubles, at least does not need to face the challenge of water scarcity, a problem that has become the centre of growing media attention in recent times. The whole region sits on 31% percent of all water reserves of Earth, while the population of the subcontinent barely exceeds 6% of all people living on the globe. As for the water supply per person per year ratio, local people cannot complain—at least not in theory.

Projected annual renewable water supply in 2025 (m3/person/year)—on a global scale, Latin America is in the first rank
Source: Wikimedia Commons, author: World Resource Institute, licence: CC BY-SA 2.5

As the above map also indicates, if one looks a bit further beyond the data, the territorial distribution of water does not show such a favourable picture. Whereas on most part of the subcontinent exposure to water scarcity is low or medium, on the western coast there is a narrow strip where the probability of such a crisis is relatively high.

The exposure of people in each country to water stress shown in the ratio of total withdrawals to total renewable supply per year (purple: >80%, red: 40–80%, orange: 20-40%, yellow: 10–20%, pastel yellow: <10%)
Source: World Resource Institute, authors: Francis Gassert – Paul Reig – Tianyi Luo – Andrew Maddocks, licence: CC

After comparing the above two maps with a topographic map of South America, it becomes evident that the most affected regions all closely align with the Andes, a mountain range that forms the part of the American Cordilleras—the largest mountain range of South America—which stretches across the entire continent.


The physical map of South America
Source:, author: Miller, licence: CC BY 4.0

The problem is mainly concentrated in the triad of Chile, Bolivia, and Peru, but even within them its intensity shows remarkable variation. Between the mountain range and the coastline, the risk of water scarcity is higher, whereas on the eastern side of the Andes the main problem is not water scarcity but the low efficiency in the use of water resources.

The map of the world split according to different types of water scarcity
Source: World Resource Institute, licence: CC

As demonstrated by the next map, the population of this specific region also follows the lines of the cordillera. This means that, while population density is higher on the eastern and western side of the Andes and particularly in the region between the western slopes and the Pacific, in the other parts of Bolivia and Peru it is lower. Therefore, there is significant correlation between areas with more people per square meter and those threatened by water scarcity.

Population density and the more significant municipalities around the Andes and at other points of the region
Source: NASA –, licence: CC BY 4.0 (

But back to the rainfall disparity between the areas that extend over the two sides of the range. This can be traced back to the so-called “flying rivers”: First, trade winds from the Atlantic transport the water evaporated at the equator in the form of clouds to the Amazon rainforests. Then, these clouds release their contents but soak up vapour transpired by the masses of forests that give off huge amounts of water into the air. At this point, the large body of moistorous air flows on to the Andes, where, hitting the mountains from the west, it ascends and discharges part of the humidity it carries. Finally, it turns to the south, and let out the remnants of its vapour in Southern Brazil. Consequently, the eastern part of the Andes receives a sufficient amount of rainfall (even in the central parts of that mountain, more than 80% of precipitation comes from the Amazon Basin), but at the same time, on the western part, there is a permanent rain shadow. Futhermore, this area, due to some other reasons, is mostly a low-pressure zone, and thus humid air masses from the Pacific also avoid it.

The route of the so-called flying rivers over South America
Source: Wikimedia Commons, author: Esmeralda59, licence: CC BY-SA 4.0

The rainfall regime in this area basically splits into two larger periods: the rainy season extends from November to April, while the dry season lasts from April to December. During the dry, water-scarce periods, glaciers formed on the Andes’ summits from earlier precipitation and the runoff water coming from them have a significant role in feeding rivers and, consequently, in local water supply, agriculture, and energy production. Their importance is underscored by the fact that 99% of tropical glaciers are concentrated in this region: 71% can be found in Peru, and 20% in Bolivia, while the rest are principally scattered across Ecuador, Columbia, and Venezuela. According to research from 2015, in La Paz, glaciers contribute to 15% of the city’s water supply on average every year; during the dry season, however, this percentage can even increase to 24%. Moreover, glaciers have an important part in the water supply of other larger cities such as Quito as well. As for energy production, one can look at Peru, where water has a more than 40% share in the country’s electricity mix, and glaciers contribute significantly to that percentage. For instance, according to some estimates, water from glaciers has a 15% contribution to the 263 MW electricity generated in the Cañón del Pato hydropower plant. In addition, glacier water has a notable share in the operation of the largest hydropower plant of the country, the hydroelectric complex adjacent to the Mantaro River.

This picture showcases how important the water from melting glaciers (indicated in blue) is to La Paz’s water supply
Source: Annals of Glaciology 2015, author: Alvaro Soruco [et al.], licence: CC BY 4.0

Beyond its role in drinking water supply and energy production, glacier water is very important to both the centuries-long traditional and the recently built-up modern and industrialised agricultural production. Therefore, glaciers are indispensable not only for the native Indian population that lives at their feet but also for agriculture, city dwellers, industry, and mines. The earlier maps have already shown that the region west of the Andes, partly supplied by glacier water, can essentially be regarded as an area exposed to water scarcity. This is chiefly due to the main temperature rise in the Tropics, which makes the glaciers of the Andes gradually recede. Since 1970, they have lost almost half of their surface area, and this trend only keeps on accelerating, while under the present circumstances the disappearing quantity is not balanced out in a natural way.

An example of glacier recession in the Andes (white represents glacier extension in 1986, blue in 2014)
Source: NASA/Earth Observatory

Projections say that by the second half of the century, glaciers will have entirely melted away from the Andes. As all the earlier information implies, their slow disappearance will not be without consequences. In the short run, however, these are not entirely negative. In Peru, for example, water abundance in the wake of the accelerated glacier melt over the last decades has actually been a positive contributor to the expansion of the export-oriented agriculture.

Yet, in the long run, these positive effects will be counterbalanced and finally replaced by negative ones. Strangely enough, water scarcity will not be the leading problem at the beginning, as in many cases, surging glacier melt might compensate for the fact that water comes from an ever-shrinking ice sheet. Nevertheless, during this first period, when glaciers will emit more water than usual, the size of glacier lakes, formed from melt water, might increase and the neighbouring soil structure might change. This may lead to floods and mass movements of ice, snow, and rock, which might pose a serious threat to the surrounding towns and infrastructure. In the long term, however, the region’s previously-demonstrated dependence on glacier water could bring even greater problems. Water scarcity may place a significant burden on energy production, transportation, tourism, intensive latifundial and traditional family farming, and water supply.

On the world’s highest (former) skiing area, the Bolivian Chacaltaya, the glacier completely disappeared by 2009, even though projections in 2005 had said that ice would last at least until 2015
Source: Shutterstock

Now, the question is what social effects will follow after all the above has happened. One possible scenario in the aftermath of the growing water stress is that the affected people, witnessing the dismantling of their subsistence, will emigrate from the zone. Even though research on such effects of the glacier melt in countries along the Andes have been scarce so far, studies has reported that this population movement has not been significant up to this point. This does not rule out, though, that glacier melt—combined with other weather changes—may elicit mass movements, or magnify some of the present patterns of mobility. Even nowadays, many rural dwellers have temporary jobs in larger urban centres in order to have an additional source of income and, thus, a more stable existence. In the future, if agricultural production dwindles, this trend might gain even more ground. Nevertheless, it is also important to note that emigration is only one of the many different ways of adaptation. This means that other adaptation mechanisms might supposedly also prove useful among the water scarcity-ridden locals.

It is also worthy of mention that present regional migratory movements occur towards big cities and metropolises, while energy, food, and water security in these places might also be likely to decrease. At the present pace of population growth, some of the bigger cities could not provide their future inhabitants with enough water even if the present quantity of water kept flowing into them. Providing that, as a result of the glacier melt, immigration towards cities increases, and urban water supply is worsened by the above-mentioned risk factors, consequences will be hard to foresee. Cities may succeed in adapting to the new circumstances: in La Paz and El Alto, for example, around 40% of the water in pipelines simply “disappears” due to the faulty system and illegal water tapping. Therefore, there is still plenty of room to optimize the system. In case this optimization does not take place or it is carried out insufficiently, and people continue moving towards cities, urban conflict might increase in its frequency and intensity. It might also happen that overpopulated and underinfrastructured cities hit by social conflict will exert less attraction on migrants.

Urban water supply in Lima, Peru
Source: Flickr, author: SuSanA Secretariat, licence: CC BY 2.0

Thus, modernizing water infrastructure may help adapt to the new conditions to a certain degree. Likewise, agriculture may also switch to more up-to-date solutions such as drip irrigation to optimize water withdrawal. After glaciers are gone, rainfall in the Andes can be stored in large water storage pools, and hydropower can also be gradually replaced by other solutions. These adaptation strategies, however, are capital-intensive, and so their quick and effective introduction in the financially less sound Latin American countries is uncertain and may require the involvement of external investors.

On the other hand, some of the adaptation techniques would only bring about further problems. For example, replacing hydropower plants with thermal power stations would just make the state of the environment even worse. In Peru, there are cases where water is tunnelled from wetter areas east of the Andes to drier, densely populated western parts of the country. The appeal of these solutions involving river diversions and boring through mountains might surge, but again, the question lingers here too whether doing all this would not cause further, irreversible harms to the mountain’s ecosystem. Moreover, it is almost guaranteed that these development projects would fuel existing tensions between mountain and city dwellers, big companies and small and medium-sized farms, and different entities in the agricultural and industrial sector.

The manifold consequences of a gradually changing water supply are still hard to assess, but social tensions are bound to worsen. Particularly, because water-related conflicts have not hitherto been alien to the region: it is enough to mention the Cochabamba Water War in Bolivia between 1999 and 2000, which erupted after the water supply was privatised and prices started to skyrocket. Taking a closer look at these conflicts, apart from the direct causes such as the right to water, issues like inequalities inherited from earlier centuries, the wealth gap between the rich and the poor, unequal land distribution, and the subjugation of the interests of small and medium-sized properties to those of the latifundia, mining companies, and the industry can also be found at the root of the problem. As the quick transformation of social structures is highly implausible, both water scarcity looming over the region and attempts to alleviate it by involving private companies or using creative but artificial and environmentally dubious ways that change the uneven distribution of water between the eastern and western parts of these countries are only to further exacerbate existing conflicts. And this, by possibly reinforcing the populist trends not fully alien to the local political culture, can spark a chain of events difficult to anticipate.


Opening pic by Flickr

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