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Rising Water Table

A clear plastic cup containing wet soil is sitting in a white plastic bowl and surrounded by water.

How can you help prevent salt from destroying farmland?

Australian Curriculum links

  • Science > Earth and Space Sciences > Year 4 > ACSSU075
  • Science > Earth and Space Sciences > Year 7 > ACSSU116
  • Science > Nature and Development of Science > Year 7 > ACSHE120
  • Science > Nature and Development of Science > Year 7 > ACSHE121

You'll need

  • small tray (or bowl)
  • warm water
  • teaspoon
  • table salt
  • nail (approximately 3 mm diameter)
  • plastic cups
  • various soil types & sand
  • clay and silt

Try this

  1. Pour water into the tray to a depth of 1 cm.
  2. Add half a teaspoon of table salt and stir to dissolve. Continue adding salt until no more will dissolve.
  3. Using the nail, make a small hole in the bottom of a plastic cup.
  4. Add one type of soil to the cup to a height of about 4 cm.
  5. Stand the cup in the tray of salt water.
  6. Check the cup each day until all the water has been drawn up and evaporated. This could take a couple of weeks.
  7. Repeat steps 3 to 6 for the other soil types.

What's happening?

Over time the salt water will be drawn up through the soil due to capillary action. Once the water reaches the surface of the soil it evaporates, leaving behind salt crystals.

Salt is a natural part of the environment, found in rocks and groundwater. Salt becomes a problem when excessive amounts are drawn up into the soil profile or flushed into river systems.

Groundwater levels can rise as land is cleared and irrigated. As the groundwater moves up through the soil the water evaporates into the air, leaving the salt behind. Most plants will die if there is too much salt in the soil and the land may become barren and infertile.

Regeneration of salt affected areas takes decades, and the worst affected areas may never fully recover. Salinity is a growing problem all over Australia but perhaps the worst affected area is the Murray Darling Basin which covers a vast area including parts of Queensland, New South Wales, Victoria and South Australia. This area is extremely valuable to Australia and contributes 45% of the country’s crop producing area. A lot of research and regeneration is underway, including salt tolerant tree planting, groundwater pumping and irrigation drainage.

Further information

Visit the Murray Darling Basin Authority for further information.