top of page

WA’s most expensive flush

Apart from Antarctica, Australia is the driest continent in the world. In Perth 40% or 124GL of drinking water, or approximately two times the volume of the entire Mundaring Reservoir, is supplied from groundwater. This 124GL is pumped from aquifers and used by industry, agriculture, residents and the general community before approximately 176GL of treated wastewater (from all sources including groundwater) is pumped out to sea, all at a cost to the community. In residential homes in Australia the highest use of fresh drinkable water is the shower, which is approximately 34% of total water usage. This is followed by the toilet 26%, and laundry 23%. Other uses, including drinking, dish washing and watering the lawns, account for only 17%.

Separately, it is expected that water pumped (abstracted) from aquifers will be reduced over time due to climate change and reduced recharge through natural processes such as rain. This lack of water in aquifers can also cause other environmental issues such as tree deaths and increased salinity. So essentially what is happening is that WA citizens and industry are paying a service and usage charge for water to be pumped from aquifers, resulting in environmental issues, then paying to treat wastewater (based on land value – not the wastewater going through the systems/plants), and finally pumping the vast majority of this very valuable/precious resource out to sea.

Figure 1: Perth rainfall comparison. It often comes as a surprise that Perth receives more rainfall than London or Melbourne. Various sources.

The main solution presented by the Department of Water and Environmental Regulation (DWER) (previously the Department of Water) to improve the health of the aquifers is the Managed Aquifer Recharge (MAR), for which there are examples across WA and internationally. MAR injects water back into the aquifer for future reuse, but this is expensive given the treatment criteria. The water needs to be treated almost to drinking standards and essentially there are other uses of the water for differing qualities. Currently, groundwater replenishment or MAR makes up 2% (will be significantly more when the expanded to 28GL Advanced Water Treatment Plant aka the Groundwater Replenishment Plant at Craigie is completed late 2019 or early 2020) of our Integrated Water Supply Scheme.

Prefeasibility studies have shown a MAR scheme design recharge rate of 10 ML/d. This represents approximately 6% of total waste water that is pumped out to sea from Kwinana and, as population growth means higher waste water volumes, this percentage will likely decrease.

The recent Waste Avoidance and Resource Recovery Strategy 2030 - DWERs current consultation piece “Legislative framework for waste-derived materials” essentially doesn’t talk about the water component of wastewater, even though it is a valuable waste stream, just the by-products. If you’ve ever drunk water in the Netherlands it has on average been through the equivalent of seven sets of kidneys before reaching your glass.

The water is owned by the crown and in theory can be accessed and used by any party through the DWER. So why isn’t more wastewater being accessed by industry and agriculture for alternatives uses? Essentially, it comes down to getting access to the pipelines that are currently monopolised. WaterCorp’s mandate is to recover costs however if the costs of this waste water are charged at WaterCorp rates, it is often uneconomical and nothing happens. We’ve seen a variety of projects die this way. The focus needs to be broader than the WaterCorp and involve the private sector (industry and agriculture) to incentivise them to use the water for further economic development, which is far more valuable and creates significantly more money for the state.

During 2017-2018 the Kwinana Water Reclamation Plant (KWRP) processed 10.25 ML/day from the Sepia Depression Ocean Outlet Landline (SDOOL) for use by industry. Of this, 6.73 ML/day was used by industries in the Kwinana area and the remaining 3.52 ML/day redirected back into the SDOOL. Industry discharged approximately 4.13 ML/day into the SDOOL.

It is difficult not to see that pumping waste water out to sea is a misuse of a valuable community owned resource, does not support state government economic development policy, blocks other users from the water, costs money and could be construed as environmentally pernicious. We are working with irrigators who would be prepared to pay 50 cents a kL, (the nutrients in waste water are a bonus not a penalty for many irrigators). This money should not be paid to WaterCorp but to whoever develops the relevant economic development assets that use this water. Assuming 60% of the 176GL can be used this is 106GL at 50cents per kL (see the water pricing assumptions below) is approximately worth $53 million dollars with no additional costs to government. With a gold price of $2,290 per ounce this equates to 23,144 ounces of gold flushed every year out to sea and the reason why WA’s second Golden Mile is actually off Garden Island. If this water was used, we have calculated that the economic, social and environmental benefits are a minimum eight to ten times this cost. So when you’re next travelling to Rotto, look south and imagine a river of liquid gold heading west.


Water Corporation – Performance Compliance Report 2017-2018 - Ministerial Statement 665 2017-2018 - Table 1 – Volume of treated wastewater discharged via SDOOL

Australian Government -

Report to National Water Infrastructure Development Fund : Western Trade Coast Managed Aquifer Recharge of Treated Wastewater for Industrial Water Supply Feasibility Study April 2019

Water Corporation – Performance Compliance Report 2017-2018 - Ministerial Statement 665 2017-2018

Israel recycles 87% of their waste water. Israel Waste Authority 2016

Perth Mint pricing 29 August 2019

bottom of page