For members of the Whitehorse Canoe Club in Victoria, river levels are essential information.
Club president Lawrence Cavedon said on some rivers a few extra inches of water could mean the difference between a thrilling ride and a cancelled trip.
Unlike Queensland, where some rivers have swollen due to recent heavy rain, summer falls were not usually the problem for the Whitehorse Canoe Club.
It has been more common for trips to be cancelled due to a lack of water.
"We're constantly making decisions," Mr Cavedon said.
"If the river's low right now, but it's dropping — is there going to be enough rain for us to paddle in it?"
Vital tool for dam operators
Mr Cavedon said the task will become a lot easier with a new online tool, jointly developed by CSIRO scientists and the Bureau of Meteorology (BOM), that forecasts river levels up to a week in advance.
Until now, forecasters could only track river levels one day at a time.
Beyond recreational use, the streamflow forecasting service is expected to be a vital tool for dam operators to judge the timing and volume of water releases.
That is especially important during the current La Nina event, which is forecast to bring above-average rainfall to eastern and northern Australia from now until early next year.
CSIRO water forecasting team leader David Robertson, who developed the statistical methods behind the forecasting tool, said the increased flood risk made the job of managing catchments and water infrastructure that much harder.
"This is especially so if the dam is at near-capacity, the surrounding soil is already saturated, and heavy rain is forecast for downstream tributaries," Dr Robertson said.
"It is one more tool in the toolkit to give people the heads-up we are expecting high-flow conditions, so let's start to plan what we would do if flood conditions eventuated."
Remote monitoring
The new tool, accessible on the BOM website, uses water data from 209 sites around Australia.
Underwater devices placed in river beds measure water levels and send the data to river-bed monitoring stations.
The information is then used to give an hourly picture of how likely a river is to rise or fall in the coming week.
"The computer models simulate rainfall, surface run-off — based on how much water is already in the soil — and river flow," Dr Robertson said.
"These simulations are updated regularly with real-time data from BOM's national network of rain and river-flow gauges."
BOM researcher Dr Prasantha Hapuarachchi said the information was valuable for risk management.
"Dam operators want to know how much flow is coming into a reservoir from upstream so that they can plan water releases safely and efficiently," Dr Hapuarachchi said.
"If there are natural flows coming into the main river from tributaries downstream, they may be able to save that water.
"For all of these sorts of operations, they need to be able to plan five to seven days ahead."
Raising the alarm
Water forecaster James Bennett said a lot of flood forecasting at BOM had been done manually.
"BOM has a lot of highly trained hydrologists who develop the flood forecasts —they tune their models in real time," Mr Bennett said.
"It's called 'in-the-loop forecasting' and it really does allow them to communicate directly with emergency services managers about what's going to happen.
"That's a tremendous benefit, but it's also labour-intensive, so if you want to expand the service, it's not so easy."
Mr Bennett said it took a long time to train hydrologists to understand the uncertainty in these forecasts and to be able to issue them.
The new tool should make it much easier.
