Flow Rate and Plant Growth

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Updated on Apr 16, 2013


How does flow rate affect plant growth in streams and rivers?


  • 20 gallon aquarium (or larger)
  • Electric water pump (found in garden stores)
  • Soil from the bottom of a stream
  • Plants from the bottom of a stream
  • Collection containers (one-gallon plastic milk jugs work well, as do plastic storage containers, or old pots).
  • Shovel
  • Scale


Experiment #1

  1. Make sure you have permission to remove approximately two gallons of silt and pebbles, water, and several plants from a stream bed. Remove these materials. When collecting the plants, make sure they are the same species, the same size and that they will fit comfortably in the aquarium without crowding. When collecting the plants, use the shovel to make sure you get enough of the silt that it is anchored in.
  2. Place your aquarium in a well-lit area near an electric outlet. Put the collected silt and pebbles into the aquarium.
  3. Gently towel off both plants. Weigh each one separately and record the weights.
  4. Plant the two plants in the aquarium, with one on either side of the tank.
  5. Set up your water pump, following the directions on the package.
  6. Position the tubing so that it shoots water directly on one plant, but not on the other.
  7. Every day for two weeks, observe the plants at both ends of the tank. Log your observations of both plants daily for at least three weeks.
  8. After three weeks remove the plants from the water. Gently towel them off to remove excess water. Weigh and record the weights. Calculate the differences between these weights and the weights in step three. Identify which plant grew most.

Experiment #2

  1. Find a creek or stream that has a bend in it. Identify the inside and outside of the bend,
  2. Measure the flow rate on either bank of the bend by noting how long it takes a flowing object to travel a specific distance. Usually, the flow rate on the outside of the bend is greater than on the inside.
  3. Examine the plant life on either side. Identify a species that grows on both sides. Tag several of these plants and measure them every day for several weeks.

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