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