Soil Infiltration

TillerName: ______

How much rain do we need before the nature center wetland is filled? How much rain can fall in the Verona area before the SugarRiver reaches flood stage? The amount of water that can percolate into the soil in a given time is referred to as its infiltration rate. Stream levels in flood stage are a function of direct runoff (water that does not infiltrate into the soil). From the infiltration rate, it is possible to calculate the size rainstorm that is necessary before flooding can occur. If you know this, you can build structures that prevent flooding. One example of this kind of structure is Harriet Park. Thus, knowing the infiltration rate of given soils is very important for city planners.

We can determine the infiltration rate for a soil through a simple measurement and calculation. By pouring water into a tin can that has been partially buried in the soil, we can record the time it takes for fixed volumes of water to infiltrate into the soil.

Procedure: You will be measuring the infiltration rate at two sites in your habitat.

  1. Clear litter from the site where you intend to measure the infiltration.
  2. Place the can into the soil up to the large unnumbered line (5 cm. from the bottom). You may need to tamp the can into the soil. Be sure to put on your safety goggles if you use a hammer.
  3. Pour entire contents of one water jug into the can.
  4. Immediately record the level of the water and start the stopwatch.
  5. Record the level of the water after each minute until water has moved below the lowest mark. Round to the nearest line. When this is the case, you may stop your experiment.
  6. After you have collected data at two sites, return to our meeting place.

Data:

To calculate the infiltration volume, use the following equation:

Volume = r2X

 = 3.14X= distance the water went down

Now plot up infiltration rate vs. time for both experiments.

Analysis:

  1. Which soil has a greater infiltration rate? How do you observe this graphically?
  1. Why do you think this soil has a greater infiltration rate?
  1. What makes this estimate of the infiltration rate a minimum estimate? Explain.
  1. What makes this estimate of the infiltration rate a maximum estimate? Explain.
  1. How could we improve this experiment to give us a more accurate estimate of infiltration rate?
  1. What natural effects might change the infiltration rate?
  1. How do humans affect the infiltration rate in the Verona area?
  1. Well-drained soils are important for farming in this region of the United States. Which habitat would have the best soils for farming?