One of Australia's greatest hidden gifts is an enormous water resource far below the ground. Spanning four states and territories it is the Great Artesian Basin, the largest artesian water basin in the world.  

The GAB's water is ancient, falling as rain or leaks from rivers west of the Great Dividing Range over a million years ago. That water goes west and down one to five metres a year percolating through cracks in sandstone sheets held together under pressure from the impermeable stones.  

It emerges to the ground naturally under pressure through springs and geological faults. Native plants and animals relied on springs in parched landscapes. Burial sites 20,000 years old showed evidence of trading posts alongside artesian springs. Use of bore water dramatically increased with the arrival of Europeans.

The first bore in 1878 found water 53m below the surface at Killara in NSW. Within 10 years, there were substantial finds in Queensland.The Barcaldine bore pumped 700,000 litres a day unleashing a drilling boom in the central west. By 1900 there were more than 500 bores in the Basin.

Initially the pastoral industries took the most water but more recently water release by oil and gas has caught up. Tourism spas and mining of copper, uranium and coal also depend on artesian water.

Human activity will unlikely ever dry up the Basin. In 120 years of bores about 0.1% of the total water was extracted from the Basin. But it has lowered the pressure of water, sometimes by 80%. A third of bores have stopped flowing altogether. The springs have been severely damaged by excavation, stock and humans while exotic pests degrade the area around springs.  Early bore technology was flawed too with many leaking and most were uncontrolled in their discharge of water, and 95% of the water ended up into open drains.

NSW introduced licensing of bores and bore construction standards. In 1990 governments agreed on a Great Artesian Basin Sustainability Initiative (GABSI) to cap and pipe bores. Across Australia capping programs rehabilitated free-flowing bores and replaced drains with pipes but the majority of the 3000 uncontrolled bores and 34,000km of open drains remain in place.

(To be continued, Thursday) DB