Rainforests in the right place are highly desirable ­ but there are some locations where you just don't want things that look like rainforests to grow, according to Peter Hick of CSIRO Exploration and Mining.

In parts of arid Australia, some mines have to pump out millions of tonnes of groundwater to keep the pit operational. If released on the surface, the water would cause an area of water-loving trees and shrubs ­ a forest that would die as soon as mining operations ceased.

Dr Hick and colleague Ms Cindy Ong are using satellites and airborne remote sensing to study the impact of mining on the vegetation of Australia's arid, semi-arid and tropical regions.

"This is a real issue for many mining operations in northern and central Australia today, because they are often located in or close to very sensitive areas such as national parks ­ and the name of the game is to create as little impact and disturbance of the native ecosystems as possible," he explains.

"If you're not aware of it, you can turn natural ephemeral vegetation into a permanent waterhole and completely change the distribution of plant and animal species.

"Then, 20 or 30 years later when the mine closes, there will be a huge die-off of the artificial environment."

Spectral analysis of aerial images reveals the long-lasting impact on fragile arid ecosystems of the mining operations of an earlier generation ­ but it also provides an excellent early warning tool for predicting possible impacts of modern mining, enabling the mine's environmental managers to avoid or minimise them.

"Water is a problem for all our iron, uranium and other mines which go below the water-table in inland and tropical regions.

"Many of them are as much as 40-55 metres below the water table, and pumping all that water out can create temporary inland lakes and flowing rivers of initially quite good quality water."

A second problem is that, by pumping out the pit, the mine "steals" groundwater from under sensitive species such as coolabahs and some of the deep-rooted arid species which rely upon it.

The challenge, says Dr Hick, is to put the mine water back into the environment in such a way that it does not disrupt the present pattern of vegetation ­ either by creating an artificial drought or an artificial flood.

The science is complex. The team use isotopic analysis to identify precisely which body of water the native plants are reliant on, and whether it is deep and constant or shallow and sporadic.

They use aerial images to work out how the water moves across (or below) the landscape as well as conventional hydrology and soil types. They also try to calculate how old the water is ­ and how long it takes to recharge its underground sources. In arid areas this can take decades and sometimes even centuries.

This gives the mine's environmental manager some clear data to work with in planning how best to dispose of the water pumped out of the mine ­ whether to keep it in artificial ponds and allow it to leach gently back, or inject it directly into particular aquifers.

The team also use satellites to study the impact of Outback roads and rail lines on the arid landscape: because the terrain is usually flat, water from sparse rainfall spreads across it in sheets and the local mulga depends on this type of watering, says Dr Hick.

But even the slight obstacle posed by a railway or road may alter the amount of water received by vegetation ­ damming it on one side, maybe causing waterlogging, and generating an artificial drought that kills the scrub on the other.

Even culverts, which are designed with the best -possible engineering, can distort the picture, creating fans of well-watered vegetation alongside triangles of dead and dying plants.

Since rail lines and tourist roads are often cut through national parks, it is important to understand these processes so as to minimise their effect on the surrounding vegetation and wildlife, he says.

More information:
Dr Peter Hick, CSIRO Exploration & Mining 08 9333 6321
mob. 041 991 2065
Ms Cindy Ong, CSIRO Exploration & Mining 08 9333 6243
Mr Chris Priday, CSIRO Exploration & Mining 02 9490 8247
Email: p.hick@dem.csiro.au