Monday, 4 June 2007

Area of Australia Covered by the Great Artesian Basin

A few days ago I did an internet search to try and ascertain the area of Australia that covers the Great Artesian Basin (GAB). It just so happens that the Australian Government’s Department of Environment and Water Resources published on the 7th May 2007 a new map addressing this very question, which I found at the following web address:

There are many people who believe that underground water can be found at any location in Australia if one drills deep enough into the earth’s surface. After seeing just how extensive the GAB is it’s easy to see how this view can be formed. In a recent discussion with the wife of the bloke who did the drilling on our place to try and find bore water she suggested that a large percentage of the underground water in Australia come from the rainforests of New Guinea to the north. The map of the GAB actually appears to support this theory.

A few days ago I was speaking with a bloke who works for one of that northern NSW Catchment Management Authorities. He told me the following:
1. In most parts of South Australia the bores to the GAB are only around 200 metres deep, at which point the water level is reached.
2. There is a project underway that will see 1200 open GAB bores capped, and that this project is well advanced.
3. In NSW bore depths to the GAB range from 300 metres to 1400 metres
4. The current problem with bores accessing the GAB is not a fall in the level of water but rather a substantial drop in the pressure … which means that some bores now have to be pumped, rather than it naturally coming to the surface.

On another matter connected with underground water, I was talking to a bloke from near Adelaide the other day and he told me about the mountain range that is just to the west of Adelaide which rises to over 1200 feet above sea level quite quickly. There is a narrow strip about 400 metres wide just to the east of the top of this ridge that gets about 54 inches of rain per annum due to the topographical impact connected with air carried moisture and weather patterns. The geology along the ridge where most of the rain falls is sandstone – quite porous. A great deal of the water that falls along the narrow strip goes straight underground and rapidly recharges the local water table, from which many of the local source water for vegetables and fruit trees and such like. Apparently this is one of the few water tables in Australia that are in fact recharging regularly. Those living as little as 500 metres away from the edge of the ridge receive annual rainfall around half or what falls along the narrow strip. Pretty neat I reckon!