7-day Streamflow Forecasts
About
Overview
Delivery of improved water availability forecasts is a key function for the Bureau of Meteorology under the Water Act 2007. The 7-day streamflow forecasting service will provide streamflow forecasts with a lead time of up to seven days to assist river users with decision-making.
This forecasting service has been developed to support solutions of the following water management problems:
- optimal irrigation and reservoir management;
- environmental flows; and
- minimisation of transmission and evaporation losses which can be considerable under stressed conditions.
- allow dam operators to make best use of natural flows in conjunction with managed releases to achieve environmental outcomes with less water;
- avoid water wastage that occurs when irrigators refuse water deliveries because a rainfall event has occurred between ordering and delivery of the water;
- support dam operators to manage dam releases in the lead up to flood and high flow events; and
- support tourism by providing information that recreational users can access to identify when conditions are good for water skiing, canoeing and fishing etc.
About the forecasts
Flow forecasts are generated daily at between 9:00AM and 10:00AM AEST. These are available as deterministic forecasts (see below for definition).
Forecasts are generated by a computer based system which uses the rainfall runoff model called GR4H as a core component. The GR4H model, initially developed by Irstea, calculates the volume of rainfall landing on a catchment, the proportion of that rainfall that becomes runoff and the way in which that runoff accumulates as it travels downhill and collects in streams and rivers. It also calculates how wet the catchment is on any given day by taking into account infiltration of rainfall into the soil, seepage of soil moisture and evaporation. The model performs the calculations at an hourly time step.
The rainfall forecast that is used in the rainfall runoff model comes from the Bureau's ACCESS (Australian community climate and earth-system simulator) Numerical Weather Prediction (NWP) model suite which produces outputs that include gridded rainfall predictions.
Deterministic forecasts
The deterministic forecast is the basic model output. The rainfall runoff model is run with the best estimates of rainfall, model parameters and catchment conditions to produce the forecast streamflow. Differences between observed and forecast streamflow are due to factors that include:
- rainfall runoff model error;
- rainfall and streamflow observation errors; and
- inaccurate rainfall forecasts.
The deterministic model output does not provide any information about the likelihood of the forecast streamflows occurring. The forecasts can be viewed as time series charts or as tables.
Probabilistic forecasts
Probabilistic forecasts provide estimates of the likelihood of a range of streamflows occurring at any given time throughout the forecast period. Methods to estimate this uncertainty through the use of model ensembles are being investigated and will be made available in subsequent releases of the product.
Disclaimer
These forecasts are automatically generated from hydrological forecasting models using recorded rainfall and river level data, and rainfall forecasts from numerical weather prediction models. All products available on this site are subject to the Bureau's copyright and disclaimer policies.
More information
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You may also be interested in reading this information sheet.
