FYFD

Tag: civil engineering

  • The Puquios System of Nazca

    The Puquios System of Nazca

    The arid Nazca region of Peru is dotted with spiral-shaped indentations, part of an irrigation system that helped indigenous civilizations thrive here before European contact. Although the region’s rainfall varies year-to-year, it never amounts to much. So pre-Columbian Nazcans turned instead to underground aquifers to gather and transport water.

    Aerial view of multiple puquios chimneys, part of a pre-Columbian irrigation system.
    An aerial view of several puquois chimneys near Nazca, Peru.

    Aquifers in the region slope downward, following the local geology. Puquios builders began by digging a preliminary well in the highlands, tunneling down until they reached the aquifer. Then they built a horizontal tunnel underground, sloping gently downward, toward the location where water was needed. Along that roughly horizontal tunnel, they built additional chimneys, the spiraling mouths of which are seen above. These chimneys are thought to serve multiple purposes. They provide maintenance access to the aqueduct tunnel, and their shape may help funnel wind underground to oxygenate the water and help keep it flowing. Eventually, the underground tunnel would exit into an open trench and a reservoir, providing year-round water for irrigation and personal use.

    Illustration of a puquios system. Chimneys upstream provide access to an underground tunnel that delivers water from the aquifer to a reservoir.

    Although the puquios cannot themselves be dated through usual archaeological means, the current consensus is that they originate from around 500 C.E., with subsequent modifications by both indigenous and colonial inhabitants. Impressively, several dozen puquios are still providing water today. (Image credits: Ab5602/Wikimedia, PsamatheM/Wikimedia, and R. Lasaponara et al.; research credit: R. Lasaponara et al.; via Eleanor K.)

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    Recycling Water

    As regions are stressed by severe drought, communities considering how to stretch their water supply increasingly turn to the option of reclaiming wastewater. As Grady explains in this video, that idea faces both technological and psychological challenges. But neither, it turns out, is insurmountable. (Video and image credit: Practical Engineering)

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    The Incredible Engineering of the Alhambra

    Begun in 1238, Alhambra Palace in Grenada, Spain is a monument to Islamic architecture and clever engineering. Despite sitting far above the city, the Alhambra was fed by the river, diverted from upstream along a canal. Within the palace itself, this water was used for heated flooring, steam rooms, baths, and even a fountain that told the time. This Primal Space video breaks down how engineers pressurized the water lines, moved water into and around the palace, and how wonders like the palace’s fountains worked. As impressive as the engineering is, though, it’s worth remembering that the Alhambra’s engineers were not creating new technologies: multiple older civilizations also used aqueducts, water wheels, and siphons to similar effect. (Video and image credit: Primal Space)

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    Dams Fill Reservoirs With Sediment

    Dams are critical pieces of infrastructure, but, as Grady shows in this Practical Engineering video, they are destined to be temporary. The reason is that they naturally fill with sediment over time. Rivers carry a combination of water and sediment; the latter is critical to healthy shorelines and stable ecology. But while sediment gets carried along by a fast-flowing river, slower flow rates allow sediment to fall out of suspension, as demonstrated in Grady’s tabletop flume. As his river transitions to a deeper, slower-flowing reservoir, sand falls out of the flow, building up colorful strata. The sand and water even create dynamic feedback loops, as seen with the dunes that form in his timelapse and march toward the dam.

    Any long-term plan for a dam has to deal with this inevitable build-up of sediment, and, unfortunately, it’s not a simple or cheap problem to address, as discussed in the video. (Video and image credit: Practical Engineering)

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    On the Mechanics of Wet Sand

    Sand is a critical component of many built environments. As most of us learn (via sand castle), adding just the right amount of water allows sand to be quite strong. But with too little water — or too much — sand is prone to collapse. For those of us outside the construction industry, we’re most likely to run into this problem on the beach while digging holes in the sand. In this Practical Engineering video, Grady explains the forces that stabilize and destabilize piled sand and where the dangers of excavation lie. (Video and image credit: Practical Engineering)

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    Dutch Water Works

    The Netherlands have a long history of extraordinary public works when it comes to water management. With much of the country’s land lying at or below sea level, massive civil engineering infrastructure is a necessity. In this Practical Engineering video, Grady takes us on a tour of Dutch water works, from the centuries-old techniques that allowed farmers to claim arable land from marshes to the unbelievably massive structures that protect the Dutch coastline from flooding and storm surges.

    For the Dutch, these projects, expensive as they are to build and maintain, are cheaper than the cost of inaction, as numerous devastating floods of the past have taught them. Although the goals are often the same — shortening the coastline, protecting land and people — the techniques are constantly evolving, especially as ecological needs of non-human species are taken into account. (Video and image credit: Practical Engineering)

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    Behind the San Antonio River Walk

    How do you manage necessary updates to an iconic landmark like the San Antonio River Walk without disrupting its function? That’s the concept behind this Practical Engineering video, which shows how the city removed and replaced two control gates for the River Walk without ever changing the water level. It’s a neat view both into the engineering of civil water infrastructure and into the practical considerations of how construction on these systems works. (Video credit: Practical Engineering)

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    How Cooling Towers Work

    Power plants (and other industrial settings) often need to cool water to control plant temperatures. This usually requires cooling towers like the iconic curved towers seen at nuclear power plants. Towers like these use little to no moving parts — instead relying cleverly on heat transfer, buoyancy, and thermodynamics — to move and cool massive amounts of water. Grady breaks them down in terms of operation, structural engineering, and fluid/thermal dynamics in this Practical Engineering video. Grady’s videos are always great, but I especially love how this one tackles a highly visible piece of infrastructure from multiple engineering perspectives. (Video and image credit: Practical Engineering)

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  • The Best of FYFD 2024

    The Best of FYFD 2024

    Welcome to another year and another look back at FYFD’s most popular posts. (You can find previous editions, too, for 2023, 2022, 2021, 2020, 2019, 2018, 2017, 2016, 2015, and 2014. Whew, that’s a lot!) Here are some of 2024’s most popular topics:

    This year’s topics are a good mix: fundamental research, civil engineering applications, geophysics, astrophysics, art, and one good old-fashioned brain teaser. Interested in what 2025 will hold? There are lots of ways to follow along so that you don’t miss a post.

    And if you enjoy FYFD, please remember that it’s a reader-supported website. I don’t run ads, and it’s been years since my last sponsored post. You can help support the site by becoming a patron, buying some merch, or simply by sharing on social media. And if you find yourself struggling to remember to check the website, remember you can get FYFD in your inbox every two weeks with our newsletter. Happy New Year!

    (Image credits: dam – Practical Engineering, ants – C. Chen et al., supernova – NOIRLab, sprinkler – K. Wang et al., wave tank – L-P. Euvé et al., “Dew Point” – L. Clark, paint – M. Huisman et al., iceberg – D. Fox, flame trough – S. Mould, sign – B. Willen, comet – S. Li, light pillars – N. Liao, chair – MIT News, Faraday instability – G. Louis et al., prominence – A. Vanoni)

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    Running Out of Sand?

    Headlines over the past few years have suggested that the world is running out of sand — specifically, that we’re running out of the angular sand grains preferred for concrete. Grady breaks down this idea in this Practical Engineering video, showing that the issue is more complicated than the shape of a sand grain. Yes, angular sand grains make stronger concrete than rounded ones for the same ingredient ratios. But concrete’s water content is also a major factor for strength, and rounded sand grains need less water to form a spreadable, workable concrete. Using less water also makes for stronger concrete.

    And though we may be short on some types of sand in certain places, sand is a manufacturable substance. We have machines and processes capable of breaking rocks into sand. It’s more a matter of choosing between the economics of mining and manufacturing. (Video and image credit: Practical Engineering)