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  Services » Regional Services » Environmental education » Resources for teachers » Classroom activities » Groundwater activities

Groundwater activities

Groundwater is water found below the earth’s surface. It is pumped above ground to be used for drinking water, as well as for industry, agriculture and horiticultural uses. Find out more about groundwater, the threats our groundwater resources face and what we can do to help keep our groundwater clean.

Photograph of flowing groundwater

What is groundwater?

Groundwater is rainwater that has travelled through the soil to underground areas called ‘aquifers’. Aquifers are areas of fractured rocks or porous sediments such as sand and gravel. These areas of fractured rock, sand and gravel act a bit like a sponge, soaking up and storing water.

The speed that groundwater flows depends on the size of the spaces in the soil or rock and how well the spaces are connected. Groundwater in the Waikato region generally moves less than one metre per day.

Groundwater makes up about 90 percent of the region’s fresh water resource. Wells pump groundwater from aquifers to above ground. We use it for drinking, in industry, agriculture and horticulture.

Around half of our region’s rural population rely on groundwater for drinking. 

The water table

The part of the ground that is always filled with water is called the ‘saturated zone’. The top of this zone is called the water table. This may be very near the ground surface or it may be many tens of metres deep. Heavy rain may cause the water table to rise, while a long period of dry weather may cause the water table to fall.

Water table activity

Have you ever dug a hole in the sand next to the ocean or a lake? What happens? If you keep digging you’ll eventually reach groundwater. The water in lakes, rivers, or oceans is surface water. Groundwater and surface water sometimes swap places. Groundwater can move through the ground and into a lake or stream. Water in a lake can soak down into the ground and become groundwater.

Next time you are near a body of water, dig down into the sand and see which way the flow is going. Is it groundwater or surface water that you find in your hole?

Groundwater contamination

Because groundwater comes from an unseen source it is easy to think that it is safe to drink. Even though soil can act as a filter, it is not able to filter out all impurities. Groundwater can get contaminated when:

  • the amount of water needing to be filtered is too great for the soil to cope with
  • too much waste water is irrigated onto the pasture and the bacteria and ‘bugs’ soak down to the aquifer
  • chemicals or pollutants enter the aquifer.

Find out more about groundwater contaminants.

Once a site is contaminated it is very difficult to clean up. Sometimes people have to find new places to dig wells because theirs have become contaminated.

Schools and groundwater

Where does your school water supply come from? Is the water that you and your students drink safe? How do you know?

Ninety schools in the Waikato region rely on groundwater for their water supply and about a quarter of these supplies are treated. Waikato Regional Council, Health Waikato and District Councils are working together to help schools ensure that their groundwater supplies are safe. Schools (Boards of Trustees) are obligated to prove that their water supplies meet current drinking water guidelines.

Waikato Regional Council is keen to protect groundwater sources for future use. The most vulnerable groundwater aquifers are shallow water table aquifers with little soil cover. School water supply wells range in depth from 5 to 185 metres and about a fifth are less than 10 metres.

Rural schools on their own water supplies must be regularly monitored to check that there is no microbial contamination. Schools, health authorities, district councils and Waikato Regional Council all have a common interest in protecting groundwater supplies.

Find out more about monitoring groundwater quality.

For more information or advice about groundwater supply protection contact Waikato Regional Council's Freephone 0800 800 401.

Classroom discussions

  • Have students investigate their home or farm products, such as paints or cleaners. Which ones would contaminate the groundwater if they were poured down the drain or dumped on the ground outside?
  • Have students find out about all the chemicals that are used at home on the lawn or on paddocks, for example, pesticides and fertilisers. Are they being applied at the recommended rate?
  • Encourage chemicals to be ‘used up’ rather than pouring unwanted chemicals down the drain. Find out about ‘environmentally safe’ products that can be used in place of hazardous ones. See if students can find out what these products are.
  • Investigate storm water drains in your area to see what is ending up in them. If your school is in Hamilton, look out for the metal fish located next to drains. Why are they there? If you live outside of Hamilton, talk to your local district council to see if a symbol can be painted (with non-toxic paint) next to the drains to highlight to people that they are flowing either into rivers or groundwater.
  • Encourage students to investigate how hazardous waste is disposed of in your area. See if a collection site where people can bring their old paint, oil, or other chemicals to be disposed of properly can be established in your area. Find out more about disposing of hazardous waste.

Groundwater activity

This activity will help students develop a picture of how water moves under the surface of the earth. Different types and sizes of rock material affect water movement. In this activity students act out how water moves through gravel, sand and clay.

Select three or four students to be the molecules of water, the rest of the class will be rock material (gravel, sand or clay).

1. Water movement through gravel

Students assigned to be gravel stand a distance apart with their arms outstretched so that they can turn around without touching anyone else.

The three or four students assigned to be water molecules then move through the gravel starting at one end and working through the other. How long did it take to get through? How easy was it to get past the gravel?

2. Water movement through sand

The students who were gravel now become sand. Get them to stand with their hands on their hips, with their elbows bent, so that the tip of their elbows touch the person standing next to them.

The water molecules move through the sand, this time experiencing some difficulty, but they should still reach the other side. How long did it take to get through this time? Was it harder to make your way through?

3. Water movement through clay

This time the students become clay and stand with their hands at their sides, huddled close together. They should be standing very close together so that it will be difficult for the water molecules to pass through.

Water molecules can then gently push their way through the clay. Some water molecules may not be able to move through the clay at all.

Discussion

  • Which rock material was the easiest for water to move through? Which was the hardest to move through?
  • How would different rock material affect the quality of our groundwater supplies?

Extension activities

1. Repeat the three models, but this time have the water molecules put a small amount of flour or powder on their elbows. Some of the powder will be rubbed off onto the rock material, while some will remain on the water molecule.

  • Discuss what the powder could represent (for example, bacteria, nitrogen or contaminants) and what affect this could have on groundwater purity.
  • Discuss how the rock material can filter some sediments and contaminants but some is also carried through to the groundwater.
  • The rock type will determine how much is rubbed off as the water flows past.

2. Have some of the students secretly place the label of a known water contaminant in their pocket. Examples could include bacteria, nitrate or arsenic. Repeat the activity with the water moving through the rock materials.

  • Ask the students if they would be happy to drink the water? Do they think the water has been well filtered by the rock particles so that it is clean?
  • Then have the students with their hidden contaminants pull their labels out and discuss what might happen if we drink water that has these things in it.

3. Carry out a real demonstration of the model using three clear containers where students can watch water move through the rock materials.

  • Fill each container with gravel, sand or clay.
  • Replicate rain falling by using a watering can or by filling a plastic bag with water and punching small holes into it.
  • Sprinkle powdered dyes on top of the rock material to simulate contaminants that might move into the groundwater.

Have students contemplate their own questions about groundwater. If you poured some water into a container of sand, where would the water go? It would go into the spaces between the particles of sand.

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