Australia makes an attempt to fight evaporationJanuary 6th, 2009 - 1:12 pm ICT by IANS
Sydney, Jan 6 (IANS) Vast quantities of water evaporate every year from a million or more farms and pastoral dams in Australia, the equivalent of three Sydney Harbours full of the precious resource. In a continent where the evaporation rate is typically four times the average annual rainfall, limiting water loss from farm and station storages is becoming a priority, according to a report released by the Desert Knowledge CRC (DKCRC).
The study looked at the scale of losses from evaporation, with particular reference to the pastoral zone and compares technologies for reducing it. It forms part of DKCRC’s WaterSmart Pastoralism programme.
It also looked at several of the new methods for lowering evaporation - floating blankets, shade cloth, floating modules and thin layers of a chemical to ’seal’ the surface. It found that high water savings are possible with these methods on dams of 10 hectares or less in extent.
It found the floating blanket of ‘bubble wrap’ could reduce evaporation losses by around 95 percent for a cost of Australian $5.50-8.50 per square metre and a breakeven price of water from $302-338 per megalitre.
“When harvested, water is commonly stored in small storages and dams, but it is estimated that up to half of this may be lost to evaporation. This represents a huge waste of our resource,” said study author Ian Craig.
“The price and value of water are increasing dramatically and the scarcity of water is the main limiting factor working against agricultural production in Australia.”
“The study indicates that Australia has over a million farm dams and storages which account for roughly nine percent of all the water stored - around 7,000 million litres,” said Andy Bubb, leader of DKCRC’s 21st Century Pastoralism project.
With such high levels of evaporation in Australia, only about five percent of the rainfall actually becomes runoff and is able to enter dams. Then, dams in the warmer areas - such as Queensland and northern New South Wales - typically lose 40 percent or more of their water volume each year to evaporation.
Even if these dams are only full half the time, the total loss could amount to more than 1400 gigalitres (1.4 trillion litres or nearly three Sydney Harbours), the study says, according to a DKCRC release.