Resource 27

Rainfall and evaporation data from the Western Treatment Plant

In this activity you will be analysing and interpreting rainfall and evaporation data collected at the Western Treatment Plant. To complete it, you will need to know how to sum data, set up tables and create a graph using a spreadsheet such as Microsoft Excel.

Rainfall and evaporation data for the years 1997 to 2002 are provided on a number of worksheets in the accompanying spreadsheet (rainfall.xls).

Exploring the data

  1. For each year, find the total rainfall and evaporation. Construct a table showing your findings and graph the results.
  2. The average rainfall for the area since records were kept is 515 mm/year. What can you say about the years 1997 to 2001?
  3. The average evaporation for the area is 1,340 mm/year. How does this compare with the results for the years 1997 to 2001?

    Look at the year 1997.

  4. Set up a table that summarises the total rainfall and evaporation for each month. Display your results in a graph.
  5. Explain the pattern of (i) monthly rainfall and (ii) evaporation.
  6. Are there any months where evaporation is lower than rainfall?
  7. What would that mean about the wastewater released into Port Phillip Bay?
  8. One of the reasons for choosing Werribee as a site for a treatment plant was the high evaporation rate over rainfall. Why do you think this is an important factor?

Further research

Find out the average rainfall for Melbourne. How does it compare with the rainfall at Werribee? Can you explain why they are different?

A good source is the Bureau of Meteorology's website: www.bom.gov.au