Research reveals best time to water your garden

A USQ student is expected to turn the gardening world on its head when she presents her research findings into the effect of cloud cover on evaporation.

Final year Physics student, Amber Young, started her research earlier this year with the aim of helping Toowoomba residents know when and when not to water the garden.

She said although advice given to residents is to water early in the morning or late in the afternoon there may be some occasions when this does not apply.

'There may be occasions when it’s not waterwise to water the garden at those times,' Amber said.

Her research shows that clouds have an indirect effect on evaporation. This means, depending on different variables, some days those times would not be suitable to water or there would be a better time of the day. There are also some days watering shouldn’t be done at all.

She said her research suggests it is better to water when there is cloud cover as it lessens evaporation.

Amber undertook the research in partnership with the Toowoomba City Council (TCC). Through her research she looked at a number of variables and their effects on evaporation by integrating a special piece of equipment, called a pryranometer, into the weather station at the Toowoomba Airport.

'Because of the problems with water the TCC wanted to get a (pryanometer) set up,' Amber said.

'It’s linked to the Australian Bureau of Meteorology and the Council wanted to put the information up on the Weather section of their website so residents can get on and have a look, and to get the awareness out there.'

Recording temperature, wind speed, humidity and solar radiation during both the daytime and at night Amber was able to see which variables effected evaporation and then how clouds affected these variables. The method she used for calculating evaporation is called the Penman-Moneith equation.

'It came out that clouds effect solar radiation, temperature, humidity and wind speed in that order, however it depends whether it is day or night,' Amber said.

'During the day clouds reduce solar radiation and temperature and increase humidity and wind speed. The same was true at night with minor variations, except for wind speed that showed significant change.

'At night if there were no clouds, there appeared to be greater wind speeds and higher evaporation, however if there was cloud cover then the evaporation dropped.

She said there needs to be more research into the effect of wind on evaporation.

'Clouds do effect evaporation indirectly, however it could be that wind speed is effecting the clouds. It is definitely something that needs to be looked into further.'

Amber submitted an abstract of her research to the Australian Institute of Physics Congress organising committee and as a result has been invited to present at the national Congress in Brisbane on 8 December 2006.

'It’s a bit scary, but it will be a great experience,' Amber said.

Media contact: Fiona Taylor, USQ Media, +61 7 4631 2559 or 0423 808 462