THE equivalent of three Sydney Harbours' worth of water is evaporating each year from one million farm dams in Australia, according to new research.
The Desert Knowledge Co-operative Research Centre study found Australia's one million farm dams hold about 7000 gigalitres and that 1.5 million megalitres was evaporating from them annually.
The greatest evaporation losses occur in the dams on Queensland and northern NSW farms that typically lose 40 per cent of their volume each year.
The study examined the cost effectiveness of a range of products in reducing evaporation, ranging from bubble-wrap covers to chemicals.
- It found:
- A floating blanket of bubble wrap could reduce evaporation by 95 per cent at a cost of $302-338 a megalitre saved.
- Shadecloth stretched on tension wires across a dam could cut evaporation losses by 60-80 per cent at a cost of $296-395 a megalitre saved.
- A chemical monolayer could cut evaporation by 5-10 per cent at a cost of $130 a megalitre.
Study author Ian Craig emphasised there was no ideal product.
He said every situation was different, depending on the local climate, the size and shape of the dam and the value of the product grown using the water.
Dr Craig said the chemical monolayer system could be used sparingly, just during the hot summer months.
The study found covering all of Queensland's estimated 55,000ha of farm dams could save as much as 300,000 megalitres in evaporation losses every year.
