Massive storms that have wreaked havoc across southeast Queensland and caused widespread flash flooding appear to have done little to raise the levels of drought-starved dams.
Although about a month’s rain was dumped across the southeast on Tuesday, with 80mm alone drenching Beachmere and a further 70mm in The Upper Lockyer in an hour, very little has found its way into the dam system.
Over the past week, which includes two huge storms in the past few days, the southeast Queensland water grid storage has risen just 0.2 per cent.
Somerset and Wivenhoe are by far the biggest dams within the water storage system but their net gain over the past week has almost been negligible.
The level for Somerset, with a capacity of 285,638ML, remains unchanged despite receiving an average of 23mm of rainfall over the past week. It was 75.2 per cent full.
Wivenhoe, which can hold 498,760ML, has received 37.6mm of rain and increased 0.5 per cent, although it’s at a precariously low 42.8 per cent.
Queensland’s bulk water supply authority Seqwater blamed parched soil around the two dams for the lack of run-off over the past few days.
Seqwater spokesman Chris Owen said Tuesday’s storm “rolled over” both Somerset and Wivenhoe but most of the rainfall was soaked up by the soil.
“It has been dry for such a long period that as soon as the water hits the soils it immediately absorbed, a bit like a dry sponge that soaks up the water,” he told NCA NewsWire.
“The storm that we saw yesterday rolled over Wivenhoe and Somerset and they received between about 10 and 25mm, so it’s enough to start drenching land.”
Mr Owen said with further rain predicted this week and more storms leading up to Christmas, that’s when significant increases were likely in the dam levels.
He said Queenslanders should not be fooled into thinking that storms equated into dams immediately being topped-up and they should continue to minimise their water usage.
“Once the soil is saturated and can’t absorb any more, that’s when you get run off,” he said.
“What’s happened so far is a good start and now we need more rain so it starts flowing into the dams.”
The combined capacity of southeast Queensland‘s drinking water supply dams, as of Wednesday morning, sat at 57.9 per cent.
The average seven-day rolling average was 56.3mm per day.
The water grid storage includes Wivenhoe, Somerset, North Pine, Hinze, Baroon Pocket, Leslie Harrison, Ewen Maddock, Cooloolabin, Sideling Creek, Lake Macdonald, Little Nerang and Wappa.
The storage capacity was calculated by dividing the current volume of water stored in the dams by the combined supply capacity.
The levels of southeast Queensland’s water grid were so parched that last month Seqwater ramped-up the desalination plant on the Gold Coast.
Mr Owen said some of the smaller dams were overflowing, such as Wappa on the Sunshine Coast, however the water gris is best served when the storms sit over Wivenhoe dam which had fallen to one of its lowest levels this century.
“Where the rain really needs to fall is Wivenhoe, because that’s our biggest dam storage and when you see significant rainfall in that catchment you will see significant increases in the combined water level,” he said.
“It‘s the lowest it has been in 10 years, you can’t ignore the fact it is less than 50 per cent full and it requires people to be aware of that and minimise the amount of water that is being used.”