Water is a fundamental component of life on earth. In contrast to the mineral, plant and animal kingdoms, it is and will continue to be, a renewable resource. Rain and snow, although irregular over short time periods and at local and regional levels, are recycled though rocks, soil and plants, eventually returning to the ocean to renew the procedure. Whilst the hydrological cycle, and the quality and quantity of water, differ immensely according to geographical location, the undisturbed biophysical environment is well adjusted to this cycle. These differences only present difficulties when the cycle is disturbed by human development and human changes.
Globally, communities and governments are expressing unease over the sustainability of natural resources. Despite the implicit timeless nature of the recycling involved in the hydrological cycle, the misuse and over-use of water raises questions of its sustainability. The quantity of water available for human use is indeed, finite. However, we still see little being done to control our use of water. In the last 100 years, water use has increased well over five times and shows no signs of slowing, within Australia alone. This figure exceeds the rate of increase in population and such long-term growth in water use is simply unsustainable. More and more often Australia is having to allocate water to the preservation of aquatic ecosystems, compounding this misuse. Water is as essential for biodiversity as it is for human existence.
The problems of Water use in Australia are reviewed in State of the Environment Australia 1996 (SEAC 1996) and are graphically illustrated in Listen Our land is crying by Mary White (1997). Water problems at a global level including those faced by Australia are described in such books as Water in crisis (Glieck 1993) and its links to the wider problems of sustainability are explored in Water and sustainability (Raskin et al.