## Let’s build an aqueduct! – activity – teachengineering electricity recruitment 2015

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Students explore in detail how the Romans built aqueducts using arches—and the geometry involved in doing so. Building on what they learned in the associated lesson about how innovative Roman arches enabled the creation of magnificent structures such as aqueducts, students use trigonometry to complete worksheet problem calculations to determine semicircular arch construction details using trapezoidal-shaped and cube-shaped blocks. Then student groups use hot glue and half-inch wooden cube blocks to build model aqueducts, doing all the calculations to design and build the arches necessary to support a water-carrying channel over a three-foot span. They calculate the slope of the small-sized aqueduct based on what was typical for Roman aqueducts at the time, aiming to construct the ideal slope over a specified distance in order to achieve a water flow that is not spilling over or stagnant. They test their model aqueducts with water and then reflect on their performance.

Aqueducts are an ancient form of transporting water, and their structural systems are still in place today, although no longer in use. Two thousand years ago when Romans built aqueducts, the objective was to transport fresh water over miles and miles of land to reach the cities. They built tall and sturdy structures with built-in channels for water to flow from its source all the way to the aqueduct end. The structures were carefully designed so the flow rate would not drain the source too quickly, while also not letting the water stand still. To ensure optimum flow rate, the channels were engineered to only drop several inches every 100 feet. Today, we are accustomed to transporting water through underground pipes using gravity and pumps, but 2000 years ago, the technology of aqueducts and capabilities were absolutely amazing and nothing like them had ever been seen or built before.

Think of the last time you walked on a bridge or saw a bridge of some sort. Do you recall what was supporting that bridge and keeping it from collapsing under your feet? Typically, engineers these days design bridges with support beams both under and above bridges for provide maximum safety. However, more than 2000 years ago when the Romans controlled a vast empire, they used an approach that was extremely innovative for its time—something that we today call the Roman arch.

The Romans created a design that enabled a structure to be much stronger (and thus safer) than anything previously seen before while using less material. These arches were so innovative and useful (and aesthetically pleasing) that almost every piece of Roman architecture involved an arch of some sort. These arch designs are still used today and can be seen in architecture around the world.

In this activity, your engineering challenge is to build a small-sized model aqueduct to transfer water from one point to another. You will design arches similar to the way the Romans did in order to support the channel carrying the water. Design your aqueduct in a way that lets water flow through the channel to the other end easily with little to no water spilling.

Why did ancient—and modern—communities build water transport systems? (See if students have ideas.) Sometimes local water sources are polluted or taste bad because of minerals in the water. Aqueducts—and modern water treatment distribution systems—are used to move clean and fresh water from a distant location to where it is needed. You may have heard of water quality and health problems in Flint, Michigan. In that town, the municipal water supply caused pipes to release lead into the tap water, so eventually the city changed its water source and treatment method. The Romans primarily used concrete, along with stone and bricks, for their water transport systems, which avoided the negative health effects of lead.

• Show students how they can use each of the tools. The laser pointer can extend a level surface to a wall so after students have calculated the drop in height of their aqueducts, they can scale and measure them using the laser as a reference point. The Popsicle sticks are useful for building the support structures and to slightly increase the arch height to achieve the perfect support amount for the aqueduct channel.

• Have students first figure out and then build arch support structures as a necessary part of building their model aqueducts to the planned dimensions. The support structure is a temporary wooden framework that supports the arch while it is being constructed and then is removed once the arch is closed and self-supporting. Direct the groups to each make one arch support structure using only Popsicle sticks, which they will re-use in the construction of all of their arches. Also alert students to be careful with the support structure and not break it since it is very important.

• Give students the constraints for building their aqueducts from point A to point B. The constraints are based on the length of the aqueduct channel. Also give students a required number of arches they need to build to hold up the bridge. For example, for a three-foot aqueduct, six arches are needed, or two arches per foot.

• Once students have finished their calculations, direct them to begin building the aqueducts. To build each arch, students need the number of blocks according to their worksheet calculations, plus blocks to place under the arches to adjust the aqueduct height. Give groups the how-to-build handout to help them build the arches.

• Direct students to glue their arches to the baseboard at distances they have calculated. For example, if building a three-foot channel with three six-inch-diameter arches, then the arches require gaps between them in order to spread them out evenly. The baseboard serves as the “land” on which the arches are positioned/attached. The placement location on the baseboard will vary by team because it depends on the arch size.

• Once students are done building, one group at a time, place a group’s setup of arches on a counter or floor, positioned with a catch bucket at the end. Then pour water into the beginning (high end) of the aqueduct and observe its flow to the other end.

• Lead a class discussion about how each group went about building its arches and the resulting performance of its aqueduct. Ask the students: What worked? What did not work? (Points to make: Ideally, aqueducts are strong and maintain their structural integrity while in use. Ideally, the water flow is not so fast that it splashes out of the channel, but not so slow as to make the water stagnant.) How would you improve your aqueduct? What process did you go through to make sure your measurements were correct? What could you have done differently to speed up the process?