Australia is one of the driest countries on Earth, and Perth is one of the driest cities in the world.
In this guide, we provide a case study on Perth’s water scarcity problems, and how they have addressed them (solutions)
Other dry countries and cities might be able to get ideas for their water scarcity issues.
Summary – Perth Water Scarcity Problems & Solutions
- Perth faced many of the same challenges as Cape Town (who experienced a recent water shortage) as a city – a rapidly growing population, a dry climate, the possible effects of climate change, decreasing rainfall and being drought prone, decrease of stream flows and flows into dams, a reliance on dams, and other factors.
- But, Perth was in a position to invest long term in options like large desalination plants and groundwater replenishment [whereas Cape Town didn’t … they relied on their dams]
- Perth’s drinking water supplies are now secure, but non potable water supply levels are decreasing
- Several sources say that Perth’s long term approach should strongly lean towards treating and re-using the waste water that is dumped from the city into the ocean and other locations, and that more desalination plants are not necessarily the right answer (desalination plants come with their own drawbacks)
- Ultimately, what will be the best water scarcity solutions for a city in both the short and long term depends on local characteristics of the city (geology/geography, and hydrology), finances, and the social, economic, and environmental impact of the different water supply options
- Diversifying water sources, and less reliance on rainfall or natural/climate based factors for water supply is a good approach for all cities for the future, as it diversifies risk and makes a city less vulnerable to climate change and global warming
- Region and state officials and water managers from places like California have visited Perth to get ideas for their own water scarcity issues
First – Define What Type Of Water Is Scarce
Water supplies can be divided into potable (drinking) water, and non potable (non drinking) water.
These types of water can be sourced from different water sources, and these different water sources can be more scarce than another.
In Perth’s case:
- Drinking water is not running out for Perth, but non potable water is
Factors Contributing To Water Scarcity For Perth
The following factors contribute to Perth’s water scarcity issues:
- A Growing Population – a growing population can mean more of a demand for water over the long term. Perth’s population grew by more than a third from roughly 2004 to 2014 (bbc.com). We say ‘over the long term’ because year to year demand can actually decrease sometimes depending on things like water restrictions and water policy, with demand for water down by 8% [in 2013] compared with 2003 in Perth.
- Despite a rising population, water consumption has fallen from 191,000 litres to 131,000 litres per capita per year over the past decade in [Perth]. In comparison, for example, San Diego’s consumption is an estimated 249,000 litres per capita per year. (theguardian.com)
- Climate Change May Be Contributing To Dry Perth Climate – climate change and global warming may be major reasons making Perth’s climate drier, with declining rainfall and increased likelihood of droughts being a side effect of climate change
- Decreasing Rainfall/Precipitation Levels – average rainfall levels have decreased in the past few decades (bbc.com)
- Perth’s annual rainfall has been declining by about 3mm per year on average (theconversation.com)
- Decreasing Rain Into Water Supply Sources – decreasing rainfall means less rain is flowing into dams and other water supply sources … about one sixth of the water is currently flowing into dams compared to the past (bbc.com)
- Water flow from rainfall into Perth’s dams has slumped by 80% since the 1970s (theguardian.com)
- [Perth’s] rainfall has declined almost 20 per cent since the 1970s, and the amount of water flowing into the city’s dams has fallen from an average of 300 billion litres a year to just 25 billion litres. (abc.net.au)
- Rising Evaporation Rates – rising evaporation rates (which increase consumption and reduce water yields). The overall effect is that soils and vegetation are often dry, meaning that rainfall will be lost to evapotranspiration rather than running off into rivers and dams, or recharging underground aquifers (theconversation.com)
- Previous Supplies Of Freshwater Did Not Have Sufficient Capacity – [In 2013] Perth’s dams received just 72.4bn litres of water – far less than the 300bn currently demanded by Perth’s two million-strong population (theguardian.com)
- Annual Mean Temperature Anomaly Has Increased – by 1℃ in southwest Western Australia in the past 40 years (theconversation.com)
- Groundwater Levels In Perth Are Decreasing, & Aquifer/Groundwater Recharge Rates Are Unknown – Perth’s hydrology means that they can use their local natural sands and aquifers to store excess run-off from roads and roads. But, there’s been less excess water from winter rains. Unlike dam inflows, we don’t yet know the full scale of the reduction in natural groundwater recharge rates. About 70% of local road runoff and half of roof runoff already recharges the shallow unconfined aquifer, because it is the cheapest way to dispose of excess water in areas with sandy soils. As well as reducing discharge costs, this practice helps to ensure that bores do not run dry in summer. Perth also has large main drains that are designed to lower groundwater levels in swampy areas and prevent inundation. Some of these waters could be redirected into the aquifer where there is a suitable site [to help in recharging groundwater aquifers] (theconversation.com)
Where Does Majority Of Perth’s Water Supply Now Come From?
- Perth now relies chiefly on groundwater and desalination rather than dams
- Although both are much more expensive than dam water, desalination and groundwater replenishment look set to secure Perth’s drinking supply, because seawater is virtually unlimited, and wastewater availability increases in line with the city’s growth
- As of 2018, desalination provides almost half of Perth’s water needs while the other half comes from ground water
How Perth Is Solving Their Water Scarcity Problems
Non Potable Water Supplies (non drinking water)
- Injecting Wastewater Into Groundwater Aquifers (Known as Groundwater Replenishment) – this is a method of recycling wastewater, where the waste water pass through sandy soil for filtering first (or gets treated separately), and then gets mixed with groundwater in aquifers, before clean water is extracted for drinking and irrigation. This has been a decade long trial for Perth that has turned out to be successful
- … treated wastewater is added to these aquifers where it blends with the groundwater and is extracted later for water supplies (theconversation.com)
- [the] treated wastewater … injected into underground supplies [has also been] re-used as drinking water (abc.net.au)
- Separate Wastewater Treatment Plants – an advanced water recycling plant can be expanded to produce 28bn litres of water each year when required … Groundwater replenishment could supply up to 20% of Perth’s drinking water needs by 2060 (theguardian.com)
Potable/Drink Water Supplies
- Desalination Plants – Large water desalination plants using sea water from the Indian Ocean via. Perth can get up to half it’s drinking water from these [two] desalination plants (bbc.com)
- These plants use reverse osmosis seawater desalination technology and provide nearly half of the city’s water supplies (theconversation.com)
- As of 2018, these plants have been able to provide one-trillion-litres of water (abc.net.au)
General Water Supply Solutions
- Awareness, & Cultural/Social View Of Water – Perth citizens see water as a scarce, valuable resource that is not to be wasted. This means they are theoretically less likely to waste it than if cultural and social norms didn’t place a high value on water.
- Openness to Drinking Recycled Water – citizens have to be open to drinking recycled water … this is easier to do if citizens view water as a valuable resource.
- Water Restrictions – for households (particularly for gardens, lawns and sprinklers) and per person.
- Backyard Bores – some citizens in Perth have backyard bores … more than a quarter have them for watering their gardens.
- Recycling (Treating & Re-using) Wastewater – instead of dumping it or releasing it into the ocean. If we can filter/clean it, and re-use it sustainably – this opens up much more available water for water supply.
- Using Natural Environment For Water Supply Processing – such as natural sands for filtering, and groundwater aquifers as storage locations.
- Become Less Reliant On Rainfall – rainfall is usually relied upon to top up groundwater and above surface water sources like lakes, rivers etc. Becoming less reliant on rainfall takes natural water replenishment means a city can shield itself from the effects of climate change more effectively.
- Diversify Water Supply Sources – relying on 2, 3 or more water supply sources is just smart from a percentages standpoint. If one water supply is diminishing, there are other options. It also helps if these water supply sources depend on both natural and man made production and replenishment for more diversification – because you are then not reliant on the climate for water supply.
- Monitor Per Capita Water Usage – this is an indicator of how effectively water is being used. Knowing both potable and non potable water per capita water usage can help cities more effectively track their water management.
- Water Saving Training, Schemes & Fines – provide businesses with free training, help in data-gathering, and a certification scheme that allows them to promote themselves as water-conscious companies. Businesses and organisations that don’t meet requirements risk fines and will be ineligible for the recognition scheme. A total of 330 businesses have reportedly saved enough water to fill the equivalent of 20,000 Olympic-sized swimming pools since the Water Corporation started this project in 2007
- Water Saving Technology – organisations have made use of acoustic listening equipment to locate pipe leaks, helping to reducing water use by 10%, & other organisations have cut their water use by 25% by reducing the flow of their taps and installing dual-flush toilets, among other things. Perth’s largest theme park, Adventure World, checks water levels and pressure using real-time monitoring. If a leak is detected, maintenance to resolve the problem can be quickly deployed. Around 30m litres of water have been saved in the past two years this way. The theme park has also installed two new filters, at A$100,000 (£46,700) a piece, saving 30,000 litres of water a day in peak season (will take 5 years to pay itself off). (theguardian.com)
- Emphasise the importance of corporate social responsibility – for businesses and organisations to save water or use it efficiently.
Long Term Questions & Concerns With Perth’s Current Water Scarcity Solutions
The above solutions and approaches Perth has chosen to address their water scarcity problems aren’t perfect. They come with long term pros and cons to consider …
- Can be expensive to build and operate – desalination plants, depending on the size, can cost billions to build, and can be very expensive to operate.
- [plants] remain costly to maintain, even if they do not supply desalinated water [and they are only on standy by mode]
- Are energy intensive – this is especially a problem when running on fossil fuel combustion.
- Can contribute to climate change – if desalination plants run on fossil fuels and not primarily renewable energy, greenhouse gases are emitted. Wind and solar energy can help with this – but these forms of energy generation can be variable and hard to use as a primary energy source for such an energy intensive process as desalination.
- Western Australian carbon emissions per capita are now the highest in Australia and among the highest in the developed world [and, desalination plants only add to this] (theconversation.com)
- Cause increases water rates/prices – use of desalination plants can increase water bills for households because of the cost to run them and the energy they use.
- The average Perth household’s water bill has tripled since 2005–06 [up to 2015], even though water consumption per capita has dropped substantially over the past decade. This adds to cost of living. (theconversation.com)
- Can damage the environment – The marine environments of Perth’s desalination plants are sensitive to the hypersaline discharge that is produced in the purification process (theconversation.com)
- Can give people a false sense that there will be fresh water available forever – this is not the case … desalination plants are not an unlimited sustainable source of water for various reasons. They still have their drawbacks and concerns for long term use.
Recycling Wastewater By Natural Filtration & Injecting Into Groundwater Aquifers
- This process relies on local factors that may not be available every where or all the time – for a city or town to use this approach, they need sandy soil in the area that can naturally filter the wastewater, and aquifers that can take the waste water too. Other cities could build wastewater recycling plants, but there would be cost and feasibility questions to answer first. The way Perth has replenished the Gnangara groundwater resource seems more of a sustainable approach
- Boreholes bored into groundwater sources can deplete the aquifer they withdraw from – Citizens having backyard boreholes can compromise the water available to the public supply via groundwater and aquifers
- All water supply sources have their own set of factors to consider short term and long term – New water sources for a city depend on when the water source is required (in terms of a timeline – how quickly), and the economics in terms of funding available and how much new water sources cost to create. You also have to consider social, environmental and economic impact overall.
What’s The Best Long Term & Sustainable Approach To Perth’s Water Scarcity Problems? – Can The Current Approach Be Improved Upon?
Several sources say an increased emphasis on treating and re-using/recycling waste water that is currently dumped into the ocean might be a more sustainable and feasible approach compared to the long term use of desalination plants …
Perth professors argue that treating and recycling waste water is a better long term approach than desalinations plants:
- [Perth has a large amount of waste water that goes straight into the ocean]
- [Perth should be sending waste water] into recharge or treatment to produce good water for public open space, even potable water
- The technology is there to treat any water — waste-water, storm water, any kind of water can be treated to perfection
On re-using more waste water instead of dumping it:
- About 140 billion litres of treated wastewater are discharged into the ocean every year in the Perth-Peel region. A further 7 billion litres are infiltrated into the sands as a means of disposal where there isn’t an option for ocean outfall. Recent investigations of these land disposal sites have shown them to be effective in protecting wetlands from drying and providing water for public and private irrigation.
- Investigations have also shown that the quality of treated wastewater can be greatly improved when infiltrated through the yellow sands into the limestone aquifer in the western part of Perth. It is suitable for irrigation after a few weeks’ residence within the aquifer.
- Without these kinds of measures, local governments will struggle to water parks and sports ovals, to protect Perth’s remaining wetlands, and to safeguard the trees that help keep us cool.
- So while drinking water supplies for an affluent city like Perth are reasonably secure, [the] vital non-drinking water supplies need to be augmented using some of the water [Perth] currently discharges into the ocean. As Perth gets even hotter and drier, and green spaces and wetlands are needed to provide much-needed cooling, [Perth] can no longer afford to let any water go to waste.
Perth & Cape Town Have Similar Water Scarcity Causes, But Have Had Different Approaches To Their Situations
- [Perth faces] very similar climatic conditions to Cape Town.
- The difference between Cape Town and Perth is that [Perth has] been in a position to make long-term decisions to deal with climate change
- [In the midst of Cape Town’s water shortage, there was] Strict water restrictions amounting to 50 litres per person per day — Perth residents use an average of 335 litres a day
- Perth, much like Cape Town, was once almost entirely reliant on its dams.
- Perth is half the size of Cape Town in terms of population, but, inflows to water reservoirs are decreasing as a result of decreased rainfall and river inflows
- There’s also been significant population growth [in both Perth and Cape Town over the last few years to decades, and more population growth is expected]
- Perth has progressively sourced more and more of its supply from desalination and from groundwater extraction – [while] Cape Town has not done this
- Cape Town has small water capacity/supply per person from it’s dams
- Brisbane has 2,220,150 ML storage capacity for its 2.2 million residents. That amounts to just over one million litres per resident when storages are full.
- In comparison, Cape Town’s four million residents have a full storage capacity of 900,000 ML. That’s 225,000 litres per resident
- Cape Town is building a number of small desalination plants to deal with this