Australia's Artesian Basin - $14 Billion down the drain each year

The present interpretation is based on the assumption that the Jurassic sandstones are porous, and that the porosity is unchanged by the discharge of water from the basin, or by the drop in water pressure. The flow of groundwater through the aquifer is considered to correspond to that of flow through porous media. This interpretation suits some of the open fluvioglacial aquifers in North America, which are radically different to our Jurassic sandstones.

These related assumptions are implicit in the descriptions of the operation of the Great Artesian Basin which are given in various government reports on the management of the Basin.

The above diagrams present a false concept of the operation of the Basin, and are repeated in many reports and publicity documents. They create false expectations about the potential and sustainability of the Basin.

This information is also included in material for Education Departments and schools, and via the Internet. It is not acceptable as an explanation to young children in schools, and is certainly not acceptable as a basis for government decisions on the management of the Basin.

The water that is now in the basin is all that will ever be available. It is a closed system. That has several implications.

When the Great Artesian Basin was first penetrated by bores, the water gushed out at high pressures and high discharges, the fountains extending 100 feet and more into the air.

That is certainly not the result of seepage through porous sandstones into a borehole, but the release of high pressure water stored in open fissures in the rock. The porosity of the sandstone rock is not a factor.

The proper understanding of the operation of the aquifer is that of an open jointed rock mass.

The water pressures in the aquifer a century ago, prior to exploitation of the Great Artesian Basin, were almost comparable to the overburden pressure of the rocks.

The original formation of the aquifer should be seen as the consequence of the effects of high hydraulic pressures in rock fissures, effectively jacking the rock apart. In this case, the extra-ordinary continuity of the sedimentary basin enabled these water pressures to open up fissures in the sandstone over great distances.

Let us first state the overall physical conditions. We are dealing with saturated, incompressible rocks, and incompressible water in fissures and bedding planes. It is a closed system.

In physical terms, the effect of withdrawal of water is a reduction of the overall volume of the aquifer by an amount equal to the volume of water removed. The ground surface subsides by an amount equal to the volume of water removed.