A group of kids huddled around a garden hose may look like a recipe for disaster, but in this case it was to prove a point about pressure. The question started off innocently enough: “What would have more pressure, the bottom of a hose that was held off a cliff, or the plug at the bottom of an Olympic swimming pool?”. Sure, one has about a gazillion times the amount of water behind it, but does that really matter when it comes to pressure? Well, to put it to the test we filled up our 20m long garden hose and I got the kids to walk down the path, which descends vertically fairly quickly. 20m of hose… that has to have a bit of water in it, yeah? It should start to really gush by the time they get to the bottom of the hill. Sure enough one kid after the next wandered down the path only to find the task of holding the hose clamped shut harder with each step down.
Let’s back up a bit, and start by saying pressure is just one of the multitudes of things we are learning about in our 6 week adventure focusing on dams and hydroelectricity. I have taught this unit a few times now, and found that while the term sounds like a chapter out of an introductory engineering book, there are more than a few moments that grab the kids’ attention. Playing with water is a given, and with that in mind there are a few other tricks that can turn dams into a truly integrated learning experience, one that touches on sociology, conservation, physics, engineering, business, geography, and art to name a few.
This unit started in a place that could not have been more organic. I invited a friend Tim and his sons on a trip out the Jatiluwih, a steeply sloped area in Bali with many creeks running down the side of the mountain. In a wandering we found ourselves creek side, and the kids took the chance to cool off and play in the water. It was not long until the rocks in the creek began to pile on top of one another, and the creek slowly started to build into a pool. “This is part of childhood… playing with the flow of a river is something we all have deep inside”, I thought to myself. So why not take this inherent desire to direct the flow of water and find ways to make a great unit out of it. Without another thought the concept of a dam unit was starting to take shape.
The first class I tried this with got the raw deal. “We’re gonna build a dam” I pronounced one day, “and I won’t give a dam for those who complain” (over the years, dam jokes have kind of taken on a life of their own). We waltzed down to the Ayung River, one of the largest rivers in Bali, and noticed an area where the river forks. One of those forks may just be manageable. For several days we worked hard to build a barrier, but the force of water tore our work away overnight with little evidence we had 24 kids toiling away the previous day. It was then I brought a few rice bags into the equation. Hadn’t I seen in every flood news story there ever was a stack of neatly piled polyester sacks holding back the floodwaters? This made our progress noticeable, and by the third day we had a proper dam along the branch of the river and were in control of about 30cm of head (this is a fancy way to say the water was 30cm higher upstream from our dam than downstream). The issue came when we celebrated “mission accomplished” and started the pack up. The sand was bound to wash downstream, but those bags… how do we get those out? We ended up slashing them and having a large pile of dirty non-biodegradable plastic that was bound for the dump. Uh, all in name of learning, right :p
Karma is ever present in Bali though, and in the process of making this dam a thief took my man purse! Not only did it have a bit of cashola in there, but I had just picked up my passport from immigration, and that was stowed in there as well! Strangely enough, I had assigned a student as the media manager for the dam and she had photographed the criminal in action. Amazingly I got back everything that was taken after the school security shared the photo with the local villagers.
I learned a lot when it came to year two of this project. Instead of plastic I found much more expensive burlap bags. Sure the kids were breaking out in itchathons, but I could sleep easy knowing these would biodegrade. I also picked a better site, one where I was confident that we could really raise the water level to put some pressure on the dam. Furthermore, I organized roles for the kids like architect, engineer, and of course construction foreman. These roles allowed the kids to define their job and work better together. Oh, and I learned the value of having a media person at every dam event, so that we could keep good track of what was going on.
Now we are into the 4th iteration of this unit. With 30% more kids the challenge has become substantially larger, and through that we have learned even better processes in getting the kids engaged. Starting with a look at how dams have changed our geography and ability to live in various places has been a good start. It puts the whole idea into context. Then, the dirt comes out and we start to build… not massive scales, but on a level that allows for precision and variation in design elements.
The week following a series of dam simulations, we started to look at the science behind what we experienced in the past week. Since kids had multiple experiences to which they could relate, the concept of pressure was far less esoteric. It was obvious that a taller water column would make the pressure greater, but what happened if we build the dam with a smaller reservoir? Here, us adults were challenged to explain phenomena where intuition and logic collided, and despite the challenge of such questions most students were actively engaged in trying to figure out these questions, many relating their past week’s experience to what was happening. The truth is that the science here is both fascinating and interesting when given a context, and with something as complicated as hydroelectricity the idea of differentiated learning comes naturally… students can rise to a level that meets their needs, and once those concepts have been understood there is always a step further in this that can be taken to increase the complexity.