Experiment Infiltration & Percolation
Download printable Experiment Sheet here.
When water falls as rain, or ice melts on the ground, much of that water runs off into a nearby stream or creek. This is called surface runoff. Some of the water, however, penetrates the ground. The process of water entering the ground is called infiltration. Once in the ground, those waters need to move around - and the process of fluids moving through holes in rock is called percolation.
This experiment explores the ideal of permeability in rocks. Some rocks have more pores and better connections between them, allowing more water to move through the rock and faster. This factor helps determine how much water can infiltrate or percolate through a rock. We call the zone in which water penetrates the zone of saturation.
In this experiment we will set up a number of plastic bottles and fill them with grains of difference sizes to see if the rate of water flow through the sediment is faster or slower with larger/smaller grain sizes. We can plot this data up and calculate the permeability of the substances.
Plastic Soda Bottles
1 liter of Large and small cobbles or gravel, sand, silt, clay, and or peat to fill bottle 1/2 way
- Cut the bottoms off of the plastic soda bottles.
- Cover the tops with the coffee filters, and secure tightly with the rubber bands.
- Fill each bottle with a different size sediment. (For example one with all sand, one with peat. etc.)
- With one hand on the small bottle opening, pour the water into the large bottle opening until half full.
- Remove hand and observe. You can use a stopwatch to time the amount of time it takes to drain the water for graphing.
- Repeat with different sized sediments.
- On a piece of graph paper, plot the time vs grain size, and see the relationship between smaller grains, smaller pore size and lower permeability (time).
Questions to consider:
- What did you notice about how the water flowed? Did larger or smaller grain sizes yield faster drain times?
- What effect did the size of the rocks seem to have on the movement of the water?