The streamflow figure shown is for all dams that supply the Integrated Water Supply Scheme, our largest scheme providing water for Perth, Goldfields and Agricultural Region and some parts of the South West.

Streamflow is recorded for the water year (May to April), it measures how much water flows into our dams and is a cumulative figure. The figures shown here include the Stirling and Samson Brook Dams.

The water in our dams is no longer made up of just streamflow from rain. Groundwater and desalinated water are stored in these dams during periods of low demand so it is available when it is most needed in the hotter months. Learn more about streamflow and why it's so important.

Our water overview

Updated: Friday, 04 December 2020 Learn more about how this data is updated

To 9am

0.00

mm

May total

May average*

32.20

mm

88.70

mm

Current

42.5%

268 GL

Last year

45%

284 GL

Change

5.7%

-16.2 GL

* Average monthly rainfall (for the period 1876 - 2016).
Dam volumes, rainfall and water use data is updated every working day, streamflow is updated weekly.

Data is cumulative for each year selected.
Select each point to see streamflow.

How climate change is impacting our water sources

Water sources for our largest scheme, the Integrated Water Supply Scheme (IWSS) which supplies Perth, the Goldfields and Agricultural Region and some parts of the South West have changed dramatically. Water for the IWSS is now comprised of a combination of sources, including desalinated seawater, groundwater, groundwater replenishment and streamflow into dams.

Traditionally, Perth relied heavily on streamflow into our dams as a water source, but declining streamflow has meant dams now play a bigger role as storage reservoirs. The water in our dams is no longer just made up of inflows from rain. Groundwater and desalinated water are stored in these dams during periods of low demand so it is available when it is most needed in the hotter months.

How Perth's water sources have changed

In 2019-20 the breakdown of Perth's water sources (IWSS) consisted of:

Desalination icon
%
Desalination
Groundwater icon
%
Groundwater
Dams icon
%
Dams
Groundwater replenishment icon
%
Groundwater replenishment