Moving groundwater

Groundwater is water that flows beneath the Earth’s surface. It’s often down very deep, and travels in a variety of ways – through cracks, porous aquifers and underground cave and stream systems. Groundwater can be hard to see and measure, but scientists can use mathematical models to make predictions on how groundwater moves. One important factor when developing these models is understanding how quickly water moves through the different types of sediments. This is something students will observe in this practical activity.

Image

You will need:

• Retort stands, clamps and boss heads to hold large funnels.
• Stockings or cloth, rubber bands and labels or pens.
• 2 x large beakers.
• Samples of sediments of various sizes (e.g. coarse sand, fine sand, gravel, pebbles, soil).
• Stopwatch.

What to do

1. Set up the funnel with the retort stand so that it is suspended above a measuring cylinder.
2. For each sediment or soil sample: place the sample in the funnel until it is about half full (Note: To make this a good scientific test fill the funnel to the same level each time).
3. Put the measuring cylinder under the funnel.
4. Pour 200 ml of water into the funnel using the beaker.
5. Start the timer as soon as you start pouring the water into the funnel.
6. In the results table, record how long it takes for water to start coming through the funnel. At the end of 2 minutes, observe and record the volume of water that is in the measuring cylinder.

7. Repeat this procedure for the other 2 samples.
8. When you have finished, clean up and make sure that you do not tip sediments down the sink.
9. Record your observations in your notebook, and draw the equipment you used. Things to consider are:
   • Did the water flow through the samples at the same rate, why or why not?
   • Which sample allowed water through the fastest? The faster water can move through a substance, the more permeable the sediment or soil is said to be.
   • Which sample slows the flow of the water the most?