Loss of salmon because of dams

Grade level: 3rd – 5th grades

Skills: Measurement (Length: inches and feet)

Related environmental issues: Biodiversity & Water

People have constructed many large dams for the purpose of flood control, water supply, and electricity generation. However, dams can have negative environmental impacts by changing the environment, affecting natural habitats in the dam areas. For example, the Elwha River in the Pacific Northwest of the United States lost nearly all of its salmon due to the construction of the two dams. A 108-foot dam and a 210-foot dam blocked their path to the freshwater stream of their origin to lay their eggs.  The dams were removed in 2014 to restore the destroyed ecosystem, and salmon began to make a return to the river after the removal.


  1. What was the hight difference between the two dams?
  2. How high were the two dams in yards?
  3. Height of the Statue of Liberty from her heel to the top of her head is 1,338 inches. Is it taller than the 108-foot dam or shorter?

Source: WWF, 2016. Living Planet Report 2016


Answer keys

1. 102 foot  (210 – 108 = 102)

2. 36 yards and 70 yards

3. The statue of Liberty is taller than the 108-foot dam by 42 inches.

108 x 12 = 1,296 inches