Climate Exchange

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Building the Seasonal

Streamflow Forecasting Service

Claire Hawksworth, Trudy Wilson, Jeff Perkins, Senlin Zhou and Bat Le,

Climate and Water Division, Australian Bureau of Meteorology

ustralia is the driest inhabited continent on Earth, with

the least amount of water in rivers, the lowest runoff and

the smallest area of permanent wetlands of all the conti-

nents.

One third of the continent produces almost no runoff

at all and Australia’s rainfall and streamflow are among the

most variable in the world. Streamflows are likely to be higher

in winter and spring in southern Australia and, conversely,

during late summer and autumn in northern Australia due to

monsoonal rains.

The Australian Government has given the national weather and climate

agency, the Bureau of Meteorology (BoM), responsibility for compiling

and disseminating comprehensive water information. Under the Water

Act 2007, BoM is working with water managers across Australia to

deliver high quality national water information to government, industry

and the community. BoMhas had longstanding responsibilities for flood

forecasting and warning services, but one of its new responsibilities

under the Water Act is providing regular water availability forecasts.

To address this requirement, in late 2008 the Extended Hydrological

Prediction (EHP) section was created within BoM to provide short-term

(up to 10 days), seasonal (up to three months) and long-term (decadal

and inter-decadal) water availability forecasts.

Streamflow information is relied on by a range of water manag-

ers and users, including irrigators, urban and rural water supply

authorities, environmental managers and hydroelectricity genera-

tors.

Predictions of short-term and seasonal streamflows, and

long-term water availability forecasts, can potentially allow these

water managers and users to better plan, operate and manage water

use; to inform water allocation, environmental flow management

and water trading decisions; and to assist with development of water

policies to ensure security of supply.

An operational Seasonal Streamflow Forecasting Service was

publicly launched in December 2010. Each month BoM issues three-

month outlooks of total streamflow volumes at a site. These forecasts

are freely available online at

www.bom.gov.au/water/ssf

for 36 sites

in 16 river basins.

The Seasonal Streamflow Forecasting Service is targeted at water

agency managers. BoM continues to work closely with key water

agency managers to ensure the service meets their needs. EHP

staff members and BoM’s Communication and Adoption team are

involved in stakeholder engagement and tailoring information to

suit users. In addition to the forecast terciles, other products such as

historical data and the forecast probability distribution and the fore-

cast exceedance probability for each forecast location are provided

on the website.

The current service is based on a statistical approach,

and a dynamic approach is being developed in paral-

lel.

The integration of these approaches in the future

will provide better accuracy, reliability and scalability, as

well as enabling the possibility of forecasts at different

timescales such as monthly or multi-seasonal.

Information incorporated in the service

BoM’s seasonal streamflow forecasts rely on stream-

flow data collected over many years by state agencies

and other organizations, as well as climate information

from BoM and international organizations such as the

US National Oceanic and Atmospheric Administration.

Antecedent streamflows, El Niño Southern Oscillation

indices and other climate indicators are used as predic-

tors in the forecast generation process. Most of the

climate indices used in the forecasts are generated

within BoM from raw data using a geo-processing

model. To produce the forecasts, most data from exter-

nal sources is downloaded from public websites and

then converted into a suitable format. Some of the

monthly streamflow data is provided directly to BoM

from water agencies, free of charge, with the forecasts

being the return benefit to the agencies.

Processes, mechanisms and capacities

The Seasonal Streamflow Forecasting Service builds on

more than two decades of BoM involvement in seasonal

climate outlooks and quality research provided by BoM’s

substantial research partnership with the Commonwealth

Scientific and Industrial Research Organisation (CSIRO).

This research partnership has taken place through the

South Eastern Australian Climate Initiative, the Water

Information Research and Development Alliance

(WIRADA) and the Centre for Australian Weather and

Climate Research. BoM’s seasonal streamflow forecasts

will be used in operational water management systems

across Australia. An example of integrated modelling

software combining river and catchment modelling

to support water planning and river operations is

eWater Source, launched in May 2012. eWater Source

is an Australia-wide collaboration effort backed by the

Australian Government and designed to boost the capa-

bility of managers to use robust and defensible science to

give advice to policy and decision makers.

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