Metro weekly water update - 6 November 2020
| Target | Actual | |
|---|---|---|
| November water use to date | 5.1 billion litres |
4.8 billion litres |
| Dam storage levels | N/A | 50.0 per cent |
| Monthly streamflow into dams | N/A | 0.17 billion litres |
| November rainfall to date | 22.4mm (Oct average rainfall 1876-2016) | 32.6mm |
| 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 816 million litres per day, which was below the forecast of 844 million litres.
Daily water use for the last 5 days
| Date | Actual water use (million litres) | Forecast water use (million litres) |
|---|---|---|
| 6/11/2020 | 877 | 857 |
| 5/11/2020 | 822 | 857 |
| 4/11/2020 | 746 | 857 |
| 3/11/2020 | 728 | 857 |
| 2/11/2020 | 740 | 825 |
| Note, water use is calculated up to 8am each day for the previous 24 hour period. | ||
Since 1 July 2020, we have used 87.1 billion litres of water – which is 1.9 billion litres above the forecast target for this period.
Dam levels (total for 15 dams)
The dam storage levels have decreased slightly this week and are sitting at a combined 50.0 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 2020 the dams have received 38.6 billion litres of streamflow. The post-1975 average for the May to April period (called the streamflow year) is 176.73 billion litres.
Sprinkler roster compliance
Since 1 January 2020, we have taken a total of 4,931 actions (warnings + fines) compared with 7,487 actions for the same period in 2019.
Annual rainfall
Perth has received 614.0mm of rainfall since 1 January 2020. The average (1994-2019) rainfall for the same period to the end of November is 716.3mm.
General water news
While Perth is renowned for having more sunny days than any other city in Australia, we used to receive a lot more rainfall than we do today.
If we still received the average amount we used to yearly, it would be enough to supply Perth’s 2 million population with all its water needs even today.
Scientists have known for some time that Perth’s rainfall was going to continue to decrease over time but what they didn’t see coming is the speed at which we would arrive where we are today. To put this into perspective, just over 40 years ago, our metro dams received an average of 420 billion litres of streamflow each year compared to 44 billion litres in 2019. That’s a greater than 80% reduction in just a few decades.
In response, our supply planners have spent the last 20 years diversifying our water sources, which traditionally relied on rainfall alone, to now climate-independent sources, such as seawater desalination, groundwater replenishment and wastewater recycling.
Read more in the feature with our environmental scientist Vanessa Moscovis.