|
WATER AND SOIL RELATED ISSUES | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| BORE WATER By artesian water, we mean water trapped in underground reservoirs of porous and permeable rock (Aquifers), often at considerable depths, and under great pressure.Much of the country west of the Great Dividing Range is very dependant on artesian water for stock watering, and even human use.Australia has several known artesian basins, which underlie some one third of the continent. The world’s largest is the Great Australian Artesian Basin, which occupies around 1.75 million square kilometres. About two-thirds of this basin is in Queensland. Artesian basins occur world-wide; the term “artesian” is derived from the locality of Artois, in France, where water under pressure was used as early as 1126 AD. The water gets into the aquifers in the form of rain water, being soaked up into outcropping structures of the aquifer. If the water does not reach the surface unassisted, that bore is said to be “sub-artesian”. In another locality, of course, the same aquifer might be tapped by a flowing artesian bore. Often, the water from a flowing artesian bore from a very deep aquifer is quite hot, over boiling point. For this reason, and for ease of distribution, water from such bores is flowed along open “bore drains”, which are simply trenches dug in the ground, allowing the water to be available to stock over a great area, and allowing the water to cool. Such bore drains extend for surprising distances, one in Queensland being 190 km long. As would be expected, open drains, in a climate as hot as inland Australia, lose a tremendous amount through soakage and evaporation. Although economically sound, it is a wasteful procedure in terms of managing a natural resource. The existence of bore drains, apart from being used by sheep and cattle, has altered the population and distribution of native animals, kangaroos in particular. In circumstances when, before European settlement, kangaroos would have died or migrated in drought periods, these animals now survive, even flourish. This places considerable pressure on domestic animals, and among the native animals themselves, through competition for the little remaining grass. Dams in dry country create the same situation. Apart from the major artesian basins, many smaller, very localised and shallow reservoirs exist, some of which are much saltier than the main basin, but which are suitable for stock purposes. Many of the windmills seen about the country are pumping from these reservoirs. It is hard to imagine that the vast supplies of artesian water could become totally exhausted, but they certainly can, and have, become lesser. The supply is obviously dependant on adequate rainfall in the intake areas. |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
   |
The
ARACARIA BORE
April, 2004
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
