Landscape image of Perth

While Perth has long been known for being the sunniest city in Australia just before the 1970’s, we still received about 20% more rain than we do today. This may not seem like a big difference, but the decrease in rain has translated to an average of over 80% in the amount of streamflow (rainfall runoff) into our dams. But it’s not just the total volume of rain that’s changed it is also the way that rain falls that’s had an impact – our rainy season starts later so we have a lot more sunny winter days now than 40 years ago, plus the stop-start nature of the rainfall we get now means catchments don’t fill up consistently through winter.

Due to the lack of rainfall across the Perth, the sources of water for our largest scheme the Integrated Water Supply Scheme have changed dramatically and the amount of streamflow (rainfall runoff)  to our dams generated from each millimetre of rainfall continues to decline.

Facts & figures

Before 1975, Perth’s dams received an average of 420 billion litres of streamflow each year, enough to supply Perth’s 2 million population even today. In comparison, between 2010-2018, Perth’s dams received an average just 72.5 billion litres of streamflow. To add to this, we now also have higher average temperatures and an increase in the annual number of days in Perth over 35 ℃, which can also lead to a spike in water demand.

In 2015, Perth’s dams received the lowest level of rainfall runoff since records began in 1911 – with just 15.8 billion litres of water. To put that into perspective, that’s only enough water to supply Perth for around 14 hot summer days.

We’ve been responding and adapting to climate change to secure water supplies for generations to come, by continually working towards our long-term targets outlined in Water Forever, first published 10 years ago. This plan adopts a three-pronged approach, which includes:

  • Working with the community to reduce water use to help defer the need for investment in further new climate independent sources;
  • Developing new water sources where necessary; and
  • Increasing the amount of water recycled.

Water for the Integrated Water Supply Scheme is now comprised of a combination of sources, including desalinated seawater, groundwater, groundwater replenishment and rainfall runoff into dams.

Did you know?

Australia’s first full scale Groundwater Replenishment Scheme is located at Craigie, in Perth’s northern suburbs. It started recharging recycled water to Perth’s deep aquifers in 2017. It has the capacity to recycle up to 28 billion litres a year, with half of this water recharging the Leederville and Yarragadee aquifers onsite and the remaining volume of water being transferred to recharge bores drilled in Wanneroo and Neerabup.

We can all help

We can all take action to fight climate change and reduce our water use. Find out what you can do to save water starting today.