The water down under
Glossary
aquifer. A layer of rock or sand that contains water. For more information see Aquifers (Tasmanian Department of Primary Industries and Water, Australia).
desalination. The removal of salts from water or soil. For more information see Desalination (Ask an Expert, Australian Broadcasting Corporation).
ecosystem. A term used to encompass all the organisms in a community together with the associated physical environmental factors with which they interact (eg, a rockpool ecosystem, a forest ecosystem).
gigalitre. A gigalitre is one thousand million (1,000,000,000 or 109) litres.
groundwater dependent ecosystem (GDE). Ecosystems that require a supply of groundwater to maintain their current structure (special composition) and function (for example, rates of carbon fixation). Some GDEs need a continual supply of groundwater, others require intermittent supply.
half-life. The time it takes for half the atoms in a sample of radioactive material to break down into a non-radioactive element. Half-lives vary significantly, from a few days for some elements to millions of years for others. Half-life measurement is important when considering the long-term storage or disposal of radioactive waste.
invertebrates. Usually defined as animals without backbones, invertebrates make up the vast majority of all animal species. Only fish, amphibians, reptiles, birds and mammals are not invertebrates. Insects, spiders, worms, slaters and many marine creatures such as corals, sponges and jellyfish are examples of invertebrates.
isotope. One of the different kinds of an atom of the same element. All atoms of an element have the same chemical properties, but the different isotopes have different weights. The different weights are because the isotopes have a different number of neutrons. For more information, see Isotopes (Carlton Comprehensive High School, Canada)
megalitre. A megalitre is one million (1,000,000 or 106) litres.
recharge or discharge. The recharge rate is the rate at which an aquifer is replenished or topped up with water (inflow). The other important variable for groundwater management is the discharge rate, or the rate at which water is taken out of the system (outflow). In some cases aquifers can discharge naturally to rivers and springs and so the water is not being removed from the system. The two variables determine the water balance, which is part of the larger water cycle involving the journey of water as it falls from the sky, onto land or sea or aquifer, and back again.
Posted February 2007.