The puquios of Nasca are underground aqueducts in the desert of southern Peru that tap groundwater and carry it to fields and homes. Their most striking feature is a line of spiral, stone-lined openings, called ojos ("eyes"), that drop down to the tunnels. In 2016 an Italian team used satellite images to map these systems and proposed that the spirals also funnelled wind into the channels to help push the water along.
A spiral puquio opening near Nasca. Photo: pikselstock/Shutterstock
That proposal made headlines as an "ancient mystery solved from space". The real story is more interesting: what the puquios do is fairly well understood, while who built them, when, and exactly how every part worked are still debated.
What puquios are and how they work
Puquios belong to a family of water systems found in hot, dry regions around the world, close in principle to the qanats of Iran. Water is drawn from an aquifer roughly ten metres below ground and flows gently downhill through a tunnel, often about a metre high and wide. Because the water travels underground, very little is lost to evaporation.
Further down the slope, the tunnel opens into an open trench. From there the water feeds irrigation canals or small reservoirs, known locally as cochas, and is used for crops and household needs.
The ojos are spaced along the tunnel, typically every 10 to 30 metres. Their wide, corkscrew or funnel shape lets people climb down to clean out silt and repair the walls, a job that local farmers have carried out for generations. Several dozen puquios still work today; a count from 2000 found 43 functioning systems, 29 of them near the city of Nasca.
What the 2016 satellite study proposed
Rosa Lasaponara and colleagues at Italy's Institute of Methodologies for Environmental Analysis, part of the National Research Council (CNR), worked with Nicola Masini and archaeologist Giuseppe Orefici. Using high-resolution satellite images, they mapped puquios across the Nasca drainage basin and compared their positions with water sources and ancient settlements.
Their key findings, as reported in April 2016:
- The puquio network was once far more extensive than the systems that survive, and the images revealed previously unknown examples.
- The placement of the systems near settlements fits a planned hydraulic network drawing on underground aquifers.
- The team argued that the puquios are pre-Hispanic, not colonial.
- Lasaponara suggested that the spiral openings acted like wind funnels, increasing pressure inside the channels and helping the water keep moving.
Speaking to the BBC, Lasaponara called the puquios "the most ambitious hydraulic project in the Nasca area", one that supplied water all year round in one of the driest places on Earth.
The wind idea is the team's interpretation. It is plausible and widely reported, but it is a hypothesis about how the openings may have helped, not a measured result. The more solid contribution of the work was the map itself.
Who built them, and when?
The Nazca culture flourished on Peru's southern coast from about 100 BC to AD 800, in the Río Grande de Nazca drainage and the Ica Valley. (Some older articles give dates such as "500 to 200 BC", which is too early.) Most archaeologists link the puquios to the Middle Nazca period, perhaps from around AD 500, although firm dates are hard to pin down.
Not everyone agrees. Some researchers have argued that the systems were built under Spanish colonial rule in the 16th century, pointing to similar Spanish mine-drainage techniques. Others counter that colonial records themselves distinguished pre-Hispanic waterworks from new ones. A broad view now holds that the Nasca puquios are pre-Hispanic in origin, with later Spanish and republican-era changes. No scientific method has yet dated them precisely, so a little caution is healthy.
Aerial view of the Cantalloc puquios near Nasca, Peru. Photo: Don Mammoser/Shutterstock
Visiting the Cantalloc aqueducts
The best-known puquios are the Cantalloc aqueducts, just outside the town of Nasca. From the air they look like a chain of spiral pits running across green fields, as in the photo above. On the ground, visitors can walk along the line of ojos, look down into the stone spirals, and in places see clear water flowing below.
If you go, wear sun protection, bring water and stay on marked paths: the stonework is old, and some systems are still in daily use by farmers.
How the puquios relate to the Nazca Lines
The same culture is famous for the Nazca Lines, giant geoglyphs of animals, plants, figures and long straight lines scraped into the desert floor. Their purpose is still unknown. Proposed explanations include images meant for gods to see, an astronomical calendar for farming, and pathways for ceremonial walks. Specialists from several fields have studied them without finding conclusive proof for any one theory.
Some researchers have linked the lines to water, suggesting that certain lines point towards water sources or puquios. That is an intriguing idea, but it remains one theory among several. What the puquios do show clearly is a society with deep knowledge of local geology and the organisation to build and maintain shared infrastructure over generations.
Why the puquios still matter
These channels are not just relics. They still deliver water in a region where it is scarce, and they offer a low-energy model for moving groundwater with almost no evaporation. Today they face pressure from deep wells and large-scale export farming, including asparagus, which lower water tables. Fewer people also know how to maintain them. Mapping projects like the 2016 study help by showing what exists and what has been lost.
The lesson for readers is simple: an eye-catching headline about a "mystery solved" usually describes one team's well-founded proposal. The puquios deserve attention for what is known about them already, and for the questions that remain open.
Sources: Space.com, 18 April 2016; Archaeology Magazine, 19 April 2016; Wikipedia: Puquios; Wikipedia: Nazca culture; original reporting by BBC Future and IFLScience; photos via Shutterstock (pikselstock, Don Mammoser).
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