DIY snow one use for Budget science cash

A scientist has proposed sending an aircraft to make more snow fall on the Southern Alps. Photo / University of Waikato

A Waikato University scientist has proposed a novel use for some of the science research funds that will be detailed in this week's Budget - sending an aircraft to make more snow fall on the Southern Alps.

Associate Professor Earl Bardsley wants to investigate cloud seeding, where an aircraft flies over high cloud and sprays it with silver iodide crystals to trigger snow. He says the technique, which is used to feed hydro dams in Tasmania, could alleviate water shortages and send more water flowing down Canterbury's rivers when the snow melts in summer.

But Dr Bardsley says it would not work on Mt Ruapehu because the mountain was too small to be confident that the snow would hit its target.

A study in Tasmania by Monash University found cloud seeding increased rainfall by at least 5 per cent compared with normal catchments.

The crystals draw water droplets together to form snowflakes, which either melt and become rain if they reach lower ground or remain as snow if they land in mountainous areas. The Chinese and United States Governments have spent millions of dollars attempting to wring more rain from the sky in dry areas.

But cloud seeding appears to be more successful in cool places that have very clean water droplets in the clouds, such as those over Tasmania and the Southern Ocean.

Dr Bardsley said many questions remained about how well cloud seeding directed rain or snow to where it was most needed. But he said a preliminary study of whether it could work in the Southern Alps could cost as little as $300,000. Actually seeding the clouds would cost more than $1 million a year.

Extra fresh water would be welcome in Canterbury, where farmers and environmentalists are at loggerheads over water needed to irrigate farms and maintain flows and biodiversity in rivers.

The added snow could build up on the mountain slopes over winter and melt into the rivers in the summer when it was most needed, said Dr Bardsley.

Snowflakes fall about half an hour after a cloud is seeded, so scientists must judge wind direction and speed and time the drop exactly to get the snow to fall in the right place.

Dr Bardsley said new research grants announced for companies ahead of the Budget this week could help irrigation companies to finance a trial.

"I'm proposing that we should carry out an experiment where you try and enhance the snow in one catchment and keep the other well separated, and over time see whether there is an increase in the amount of water flowing out [in rivers].

"Even a 5 per cent [water] increase - providing you can get a hold of the water - is worth a lot of money in Canterbury."