Parched Peru restores pre-Inca levees to solve its water problem

Peru's amuna system begins by collecting water from atop the San Pedro de Casta Mountains, nearly 13,000 feet above sea level. infiltration, allow water to infiltrate underground during the rainy season to be harvested by the villagers in times of drought.
Peru’s amuna system begins by collecting water from atop the San Pedro de Casta Mountains, nearly 13,000 feet above sea level. infiltration, allow water to infiltrate underground during the rainy season to be harvested by the villagers in times of drought. (Florence Goupil/For the Washington Post)


SAN PEDRO DE CASTA, Peru – On a mountainside above Peru’s capital, Javier Obispo pauses from the backbreaking work of renovating a Men. The abandoned irrigation dyke distributed water before the arrival of Europeans in South America.

With Lima’s water supply under increasing pressure, the 42-year-old vet tech has worked with other villagers here to bring old technology back to life. The steep slopes of the Andes, dotted with small cacti wielding oversized spines, loom around us a parched light brown. Climate change is making itself felt.

“Twenty years ago, the ground was wet. There were waterfalls,” Obispo said, pointing to a dusty cliff above. “Now there just isn’t enough pasture. How will it be in 2030?

But now the water is starting to trickle, perhaps for the first time in centuries.

The amunas – 18-inch-high permeable stone and adobe walls that run for miles through this imposing landscape – divert excess water from streams that, in the rainy season, would otherwise flow unchecked into the mountains and would eventually get lost in the Pacific Ocean.

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They then infiltrate this water into the ground, replenishing the water table and ensuring its gradual release throughout the year into natural springs. The old technology also improves water purity and helps prevent erosion and landslides.

High in the mountains of San Pedro de Casta, workers are using stone and a bit of cement to reinforce the start of the water catchment. (Video: Courtesy of Aquafondo)

Obispo is one of twelve villagers working together under the tropical mountain sun to save this five-mile-long site. Menby excavating it from accumulated earth and renovating it into a pilot project which is promising for this arid landscape.

“The amunas are the only hope,” says Obispo, who lives here in a community of 400 people. “Without them, San Pedro de Casta will die.

Yet the project, organized by local nonprofit Aquafondo, also aims to benefit people far beyond this remote region. A breathtaking four-hour drive, some 13,000 feet underground, is Lima, considered the third most populous desert city in the world, after Cairo and Karachi, Pakistan.

Nestled on the edge of the Pacific in what is effectively a northern extension of South America’s Atacama Desert, the location of Peru’s chaotic capital of 10 million people was chosen in the 1500s by conquering Spaniards rather than by indigenous resident ecologists – and has become increasingly problematic with the explosive growth of recent decades.

Employed by the NGO Aquafondo, the workers are all from San Pedro de Casta near Lima, Peru. (Video: Courtesy of Aquafondo)

Lima’s water supply is largely dependent on three small rivers that descend from the Andes and fluctuate throughout the year from dry to raging torrents whose volume can overwhelm the water utility.

The company, Sedapal, has invested heavily in altitude reservoirs above Saint-Pierre de Caste and initiated the construction of several expensive desalination plantsto remove salt from seawater. Yet Lima still suffers from a lack of water of about 100 cubic feet per second.

This means that around 1 million of the poorest inhabitants on the outskirts of the city lack running water. Instead, they rely on an unregulated fleet of tankers dispensing untreated water at rates 10 times higher than those paid by the wealthy. Lima connected to water pipes.

The deficit could be filled almost entirely by water supplied by amunas, the researchers calculated. To achieve this, Peru would have to restore hundreds of kilometers of prehistoric dykes on the three watersheds that serve Lima.

“The idea is first to help the local community, guardian of the water. Otherwise, we would just use them,” says Mariella Sánchez, Executive Director of Aquafondo. “But the goal is the same for those who live downstream in Lima: to improve living conditions.”

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The San Pedro de Casta model, which is funded by Backus, Peru’s largest beer and beverage company, and GIZ, Germany’s international aid agency, is one of many pilot projects attempted by different organizations to non-profit.

The development of amunas around 600 BC. AD, centuries before the advent of the Incas, remains shrouded in mystery because Andean cultures did not develop writing. Their revival could now be extended nationwide to benefit other coastal cities.

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As the source of the Amazon River, Peru is blessed with abundant fresh water. But 98% of its precipitation flows east from the Andes and the Amazon to Bolivia, Colombia, Brazil and the Atlantic, while two-thirds of its 33 million people live on the coastal strip. arid western part of the country.

The effects of the climate crisis in the Peruvian Andes are complex. The higher watersheds of Lima receive a little more precipitation than before, but in more intense and more difficult to manage bursts. Further down, at San Pedro de Casta, there are fewer.

Obispo says the rains that once ran from Christmas to April usually arrive in mid-January and end in mid-March. Local herds of cows and goats have fallen by 40%, he says, while harvests of potatoes, corn and beans have fallen by 30 to 50%.

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Revive the amunas could be complemented by restoration projects punathe high altitude tundra ecosystem which, when healthy, retains water like a sponge.

A consortium of non-governmental organizations, supported by the United States Agency for International Development and involving researchers from Imperial College London, has started the sensitive work to encourage mountain communities to trade their horses and cattle for more durable llamas and alpacas.

South America’s native camelids have soft pads and only nibble on grass tips – unlike imported cattle, which pull up slow-growing vegetation by the roots as their hooves compact the soil.

These green measures can be expensive 100 times less per cubic foot of water than investing in gray infrastructure such as dams and reservoirs. Sedapal sees the different approaches as complementary and equally necessary to ensure Lima’s water security in the decades to come.

For San Pedro de Casta, the advantages of restoring the premises amunas should come much faster, over the next 12 months. “It could be a turning point,” Obispo says. “We hope that some people who left the village will even consider coming back.”

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