Sand Tank Lab

Hydrology may not be a field you have heard of, but this is a branch of science that you use everyday. From the water you drink to the food you eat, we use water in every aspect of our lives. While studying water may not seem the most interesting, what is undoubtedly interesting is that water has been recycled since the earth formed billions of years ago. So the water you are drinking or showering with could have been the same water a dinosaur drank millions of years ago! This means that we have to make sure people don't use too much water, and that the water is clean because your great- great- great- grandchildren will be using the same water we use today.

One important aspect that hydrologists must understand is how water travels. Click HERE so we can work through a simulation together about understanding how and why water moves the way it does. Click the "Play" button on the simulation, and "run" the program. We will start on the first page, which is the "Pressure" tab. You should see a 'hose' at the bottom of the page, with a small arrow all the way on the left side. Move that arrow to the right, and the water starts to drain. But why? Well, gravity. Gravity pulls you and me and everything on this planet towards the center of the Earth, so it pulls water down too. Try this: scroll to the middle simulation, the one that looks like is has a right-side-up and an upside-down triangle. Open the faucet (with the small arrow) and fill the two shapes. Now open the hose at the bottom of the page again, and observe the falling water column. Do you see how both shapes drain equally? Despite being totally different? That's because gravity is acting equally on the water in both shapes.

Now go to the "Flow" tab in the middle. You should see a pipe with handles all over the top and bottom. There should be a small box with "Dots" written next to it. Click on the box to turn on the dots. Now you see these dots flowing through the pipe. Grab one of the yellow and grey handles on the top of the pipe, and move it down. Do you see how the dots move faster through the section of pipe with that's thinner? This is due to a well established relationship between velocity and area, and it's the reason airplanes fly. If this isn't obvious, click on the "Slow Motion" button at the bottom.

Now please imagine that this pipe is full of sand. This most certainly complicates things, because of friction, because water might become trapped around sand grains, and because water molecules may be attracted to the sand. If hydrology interests you at all, these concepts will be continual struggles. The beautiful thing about science though is that once you finally learn something, something that may even be entirely obvious to everyone else, you get this immense feeling of satisfaction that you understand. No one can take that away from you!