Environment Education
Environment Education
Environment Education
Environment Education

WATER

Bore and well water - groundwater - comes from rain and rivers, seeping down through layers of soil and rock which hold the water and allow its slow movement underground. The areas of "held" water are called aquifers. An aquifer may be confined or unconfined.

  • A Confined Aquifer has a layer of solid material, like rock, that overlays and confines the aquifer, forming a closed, protected collection of water. When a bore is drilled into this type of aquifer, if the aquifer is fed by a source higher than the level of the bore, the water may flow without being pumped. This is known as an artesian well.
  • An Unconfined Aquifer does not have the top protective layer, so the water level will fluctuate with the water table.

 

THE EARTH

There are three main types of rock found under the surface of the earth:

1. Igneous - Molten rock that has cooled and solidified (e.g. Ignimbrite, Basalt, Rhyolite)

2. Sedimentary - A mixture of rock particles that have compressed and cemented together (e.g. Greywacke, Limestone)

3. Metamorphic - Igneous and Sedimentary rock that is converted by increased temperature and pressure (e.g. Marble, Schist)

The way rock is formed, and what other material is with the rock determines how well water will flow through the formation.

 

WATER WELL DRILLING

Construction of a water well involves a range of tasks. The key steps are described below.

A bore is drilled to the top of the aquifer. Steel casing is inserted in the bore to form the wall of the water well. The bore is then drilled deeper, through the aquifer. Depending on the type of rock around the aquifer, a screen may be installed to minimise the amount of sand and small rocks in the pumped water. On larger bores, sometimes the space between the casing and the edge of the bore is filled with concrete - this is known as grouting. The diagram on the right shows the construction of a large diameter water well.