This week in Frannie’s exploration of the Awesome Aquifer Kit is all about exploring the key concept of permeability.
|For this experiment, you will need water,|
a syringe, a timer, sand, and gravel.
Permeability is the ability of a sediment to transmit water. In other words, permeable materials allow water to easily pass through it and impermeable materials do not let the water move through them.
We’re going to test the permeability of sand and gravel to discover which one is more permeable.
First, we will make a hypothesis about which material water will travel through the fastest. Frannie thinks water will travel through gravel more quickly than sand.
Now we’re going to take apart the syringe and fill up the inside with gravel. We’ll measure out one ounce (oz) of water with a small measuring cup and pour the water into the syringe, careful to hold it over a cup so it doesn’t spill everywhere. For extra fun, we can time it with a stopwatch and see how long the water takes to go through the gravel.
|Water flows quickly through the empty syringe on the left, a little more slowly|
through the gravel in the middle, and very slowly through the sand on the right.
Next, we’ll empty and dry the syringe before filling it with sand and, again, watching how long it takes 1 oz of water to move through it into our cup. Does the water move faster or slower than the gravel?
Frannie has found that the water moves faster through the gravel than it does the sand which means that the gravel is more permeable. She was right!
Permeability and porosity are related. Materials with more open space can hold more water. More space also provides a quicker flow of water through the material. Materials that have a higher porosity also tend to have higher permeability. Clays, however, have a very low permeability but are very porous which means they can hold a lot of water but they won’t release it very quickly. Clay and harder materials that also can’t transmit water very quickly, like shale and granite, are called impermeable layers.