Table showing target and actual water use, dam levels, streamflow and rainfall
Target Actual
July water use to date

9.02 billion litres

9.42 billion litres
Dam storage levels N/A 46.8%
Monthly streamflow into dams N/A 9.82 billion litres
July rainfall to date 167.70 mm (July average rainfall 1876-2016) 170.20 mm
Note: 1 billion litres = approximately 400 Olympic swimming pools. Please note the figures in this table are rounded (except for rainfall) to the nearest whole number.

Water use

Average water use over the past week was 638 million litres per day – above the demand forecast of 604 million litres per day.

Daily water use for the last 5 days

Table showing daily water use for the last 5 days
Date Actual water use (million litres) Forecast water use (million litres)
09/07/2021 614 594
08/07/2021 605 594
07/07/2021 618 594
06/07/2021 600 594
05/07/2021 657 601
Note, water use is calculated up to 8am each day for the previous 24 hour period.

Since 1 July 2021, we have used 9.42 billion litres of water – which is 0.4 billion litres above the forecast target for this period.

Dam levels (total for 15 dams)

The dam storage levels are slightly up on last week and are sitting at a combined 46.8 per cent* of full capacity.

*Please note some dams are filled from different sources - dam levels include the transfer of groundwater and desalinated seawater from treatment plants as well as streamflow (that comes from rainfall). As we use many different sources of water, dams are no longer an accurate indicator of the health of Perth's overall water supply situation.

Streamflow (total for 15 dams)

From 1 May 2021, the dams have received 12.8 billion litres of streamflow. The post-1975 average for the May to April period (called the streamflow year) is 175.59 billion litres.

Sprinkler roster compliance

From 1 January to 9 July 2021, we have taken a total of 3,648 actions (warnings + fines) compared with 3,450 actions for the same period in 2020.

Annual rainfall

Perth has received 497.4 mm of rainfall since 1 January 2021. The average (1876-2016) rainfall for the same period to the end of July is 543.6mm.

General water news

If you’ve been for a walk around Herdsman Lake recently you may have noticed some strange-looking contraptions floating on the water.


But don’t be alarmed, they’re in place for a very good reason. The devices are what’s known as gross pollutant traps (GPTs) and help capture litter and other material that can flow into the lake from stormwater drains. You can think of the traps a bit like floating rubbish bins.


Three GPTs have been installed at inlet and outlet points around the lake as part of a two-year trial to determine their overall effectiveness. If successful, you could start to see more pop up on other large stormwater drains around WA.


It’s all part of our efforts to ensure cleaner stormwater flowing through our network and reduce the amount of plastic pollution that would otherwise find its way into our oceans. You can find out more, and see pictures of the GPTs, by checking out the media statement page on Water Corporation’s website.