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Coastal BC Rainfall

This activity is an exploration of the amount of rain that a rainforest receives each year.

To be classified as a temperate rainforest, a forest must receive at least 140 cm of rain a year. The estimated annual rainfall of Vancouver is 146 cm. Closer to the mountains, North Vancouver gets an estimated average rainfall of 252 cm. Farther west, the estimated annual rainfall of Tofino, B.C. is 327 cm.

Meteorologists measure rainfall over a set period of time (usually one year) using a rain gauge. Most simple rain gauges are cylindrical (long tubes), have the capacity to capture the falling rain and have lines on the side to measure the amount of rainfall.

Values sourced from https://www.currentresults.com/Weather/Canada/British-Columbia/precipitation-annual-average.php

Objectives

  • Describe the characteristics of a coastal temperate rainforest.

Materials

  • volunteers

  • metre stick

  • string

  • map of British Columbia

Key Questions

  • Why are the coastal temperate rainforests located near the ocean and coastal mountains?
  • How does rain benefit the rainforest ecosystem?
  • What is the difference in forests that get 100 cm of rainfall and forests that get 300 cm of rain fall? Does all the rain fall at once, does the same amount fall all the time, or does it vary?

What To Do

  1. Examine the map of British Columbia and point out the following:
  • ​Coastline
  • Haida Gwaii
  • Vancouver Island
  • Tofino
  • Vancouver
  1. Ask students to show with their hands how much rainfall they think the temperate rainforest gets each year.
  2. Using a meter stick, have students measure out 140cm of string. This represents the minimum amount of rainfall for a forest to be classified as a rainforest.
  3. Measure out 146 cm and explain that this is the amount of rain that falls, on average, every year in Vancouver.
  4. Measure out 252 cm and explain that this is the amount of rain that falls, on average, every year in North Vancouver.
  5. Measure out 327 cm and explain that this is the amount of rain that falls, on average, every year in Tofino.

Extensions

  • Investigate how mountains affect rainfall.
  • How do we measure rainfall? See Water Savers for instructions on creating a rain gauge.
  • Compare the coastal temperate rainforest rainfall to other rainforests (e.g. Amazon). Use a stairwell or a gym wall to mark the levels of rainfall in various locations.

    Here are some rainfall extremes in Canada:Hartley Bay, a village about 140 km south of Prince Rupert, measures an incredible 455 cm of rain each year.Arctic Bay in Nunavut is the driest place in Canada. In a typical year, less than 5mm of rain and snow fall there.

    And the world:The wettest place in the world is Tutunendo, Colombia, with an average rainfall of 1,177cm per year.The driest place in the world is the Atacama desert in Chile. The average rainfall in the region is just 1 mm per year. Some weather stations in the Atacama have never received rain.