The green light for dry plants
TOWNSVILLE is turning green after months of bonedry conditions, partly because of the special properties of rainwater.
James Cook University hydrologist Dr Han She Lim said rain contained more nutrients than treated water and was more beneficial to plants.
“Rainwater is acidic and when it falls through the atmosphere it dissolves nutrients which are useful for plants and their growth,” Dr Lim said.
“It’s also better to use rainwater to water plants as treating water is an expensive process.”
Dr Lim said rain in Townsville that fell over urban areas would go down the drain into the Ross River, but in areas covered by vegetation a different process would take place.
“If you have land with vegetation like grass or trees, the rain starts soaking the soil like a sponge,” Dr Lim said
“Gradually it starts going into the ground.
“The roots loosen the soil and help the water go below.”
If it’s been dry for a long time, like in Townsville, and it rains quickly, excess water will flow off the surface as the ground can only absorb a certain amount over a period of time.
Dr Lim said rain would help fill underground aquifers, which fed rivers.
“Rivers are dry when it doesn’t rain because they’re not getting water from below the ground,” she said.
The key for this weather event is whether the water falls over the catchment areas.
Those areas are upstream of the Ross River Dam and feed it with water, which in turn provides Townsville with its supply.
Widespread rain across Townsville has to led to a sudden and visible greening of public areas including Castle Hill and The Strand.
Dr Lim said plants reacted suddenly to rain after long periods of dry.
Plants drop their leaves when it’s too dry as they don’t want water to be lost.
“When it rains the plants come alive and if the rain soaks into the ground the roots will be able to extract the water, which goes into the plant through the roots and travels through the trunk and into the leaves,” Dr Lim said.