There will be a water grid and an electricity grid right around Australia. There will be only a small number of roads, as much more will go by air.

The use of coal and oil will be minimal.

Hydrogen will be the main source of power.

The Photovoltaic technique will be extensive - that is purifying sea water or any other contaminated water.

A considerable amount of electricity will be generated by windmills and other techniques where there is a combination of wind movement created by a high tower, a mushroomed cover near ground level and generators at the foot of the tower.

All of the above techniques are now physically possible, but not yet economically viable.

A water grid is being considered even now between the states of Australia.

Both short distance and long distance flights will be more economically viable, some going higher than our surrounding atmosphere, and many others at lower levels.

Synthetic oil and oil extracted from the ground will be needed for lubrication.

The cost of making hydrogen will soon be economically viable for much wider use.

The photovoltaic technique is becoming cheaper.

There are a number of units in many countries with less sunshine than we have in Australia.

Reverse osmosis is used in Bendigo at our main gold mine.

The Persian Gulf is probably leading the way now early in the 21st century.

This with tidal flow will be important.

Techniques like the Snowy Mountains scheme are on the increase. Many sites around our coast are now viable for wind generation.

Denmark on a windy night generates all its necessary electricity this way.

Buronga in the Riverina is erecting a tower as described and it will cost about $1 billion to erect and is expected to generate enough electricity to supply the needs of 100,000 houses.

I believe Port Augusta is a good site for a major development because it is on the sea, nevertheless not far from inland Australia.

Windmills and photovoltaic units are possible.

Reverse osmosis units can be installed and the salty brine pumped back to the open ocean, the clean water pumped up to a high point in the Flinders Ranges and then piped all around Australia.

It may also be possible to make a very picturesque reservoir in Wilpena Pound for a more efficient flow of the purified water to the inland.

Constant monitoring of the subterranean water level, so that salination is avoided.

We have learnt many costly lessons on this one during the past 100 years.

KEITH STEPHENS, Bendigo