Water Scarcity Case Study Of Perth, Western Australia: What We Can Learn

Perth as a city has one of the driest climates in the world.

In this guide, we’ve put together a case study of Perth’s water scarcity problems, and what they have done to address them.

Other dry countries and cities in the world might be able to learn something about how to address their own water scarcity and water quantity related issues.

 

Summary – Perth Water Scarcity Problems & Solutions

Factors That Might Impact Water Scarcity In Perth

Factors may include but aren’t limited to:

– Low natural rainfall levels in some regions

– The potential side effects of a changing climate, such as declining rainfall, increased likelihood of droughts, increased annual mean temperature, and other climate related changes

– Declining flow into water supply sources like dams

– Rising evaporation rates

– Existing water supply storage capacity not being sufficient

– There’s less excess water running off into storage aquifers, and the reduction in aquifer recharge rates are unknown at this point in time

 

A City’s Population Size, & Water Consumption

A growing population in a city can result in increased water consumption

However, some data suggests that Perth’s water consumption decreased on a per capita basis, despite a growing population

 

The Current Status Of Perth’s Water Supplies

Some reporting indicate that Perth’s potable water (drinking water) supply is currently secure, but the non potable water supply is less secure and becoming more scarce

 

Where Does The Majority Of Perth’s Water Supply Currently Come From?

Currently, Perth relies mostly on ground water (and ground water replenishment schemes where waste water is filtered and injected into aquifers), and desalination, rather than their dams

We outline some of the potential drawbacks and limitations to these water supply methods/options in the guide below

Another option Perth is investing in is advanced water recycling plants (where waste water is treated and re-used)

 

Considering Waste Water Recycling As Part Of A Sustainable Water Supply Strategy

Some experts identify waste water recycling as perhaps the best long term solution for sustainable water supplies (even over desalination) because of it’s potential, and also because of how much waste water, storm water, and run off water we currently lose or waste

 

Other Potential Solutions To Form Part Of A Sustainable Water Supply Strategy

Other potential solutions that might contribute to sustainably managed water supplies might be:

– Increased cultural and social awareness of the value of fresh water

– Increased acceptance and openness in drinking recycled water

– Strategic water restrictions

– More effective water policy

– Backyard bores

– Using the natural environment for filtering and water storage

– Diversifying water supply sources and becoming less reliant on rainfall and natural climate related water supply factors

– Monitoring annual per capita water usage numbers

– Water conservation and efficiency training for businesses

– Considering initiatives and penalties for corporate water use

– Water saving and water leak detection technology for public water supply pipes

– Upgrading water supply pipes

– Bing aware of conflicts of interests relating to political parties and public water supply

– Balancing urban and rural water needs

 

Water restrictions and water policy can help decrease demand for water in the short term or long term.

Perth has actually decreased it’s water consumption (per capita per year) over decade long time periods, despite an increasing population

 

Different Cities & Towns Will Need Individual Water Supply Strategies

Ultimately, what will be the best strategy for a city to address water scarcity 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.

Each city will need a different strategy depending on their own local situation

Diversifying water sources, and less reliance on rainfall or natural/climate based factors for water supply might be a good approach for all cities for the future.

This diversifies risk and makes a city less vulnerable to a changing climate.

Their water sources become more independent of the variable nature of the natural water cycle and climate.

Region and state officials, and water managers from places like California, have visited Perth to get ideas for addressing their own water scarcity issues.

So, exchanging potential solutions and strategies for sustainable water supply management, and looking at what other cities and towns are doing to have success, may be beneficial for decision makers.

 

Comparing Perth & Cape Town’s Water Scarcity Issues – Similarities & Differences

Perth faced some of the same challenges as Cape Town (who experienced a recent water shortage) as a city:

– A rapidly growing population

– A dry climate

– Possible side effects of a changing climate

– Decreasing rainfall

– Being drought prone

– Decrease of stream flows and water flows into dams

– A reliance on dams

– Plus, other challenges

 

However, unlike Perth, Cape Town stayed reliant on their dams to provide a public water supply 

Perth diversified to ground water and desalination plants to diversify their water supply sources and augment supply capacity

To increase per person water capacity, Cape Town was reported to be looking into building several small scale desalination plants

Looking to diversify their water supply sources in the future, becoming less reliant of water sources that are dependent on natural rainfall and the natural climate, and increasing their per person water capacity, might all be good solutions to consider as part of Cape Town’s water supply strategy.

 

What Type Of Water Is Scarce In Perth?

Water supplies can be divided into two main categories:

– Potable (drinking) water,

– And, Non potable (non drinking) water

These categories of water can be sourced from different freshwater supply sources, with some being more scarce than others.

 

theconversation.com indicates that ‘[In Perth’s case …] Drinking water is not running out for Perth, but non potable water is’

 

theconversation.com: ‘… drinking water supplies [in] Perth are reasonably secure [but] non-drinking water supplies need to be augmented …’

 

Factors Contributing To Water Scarcity For Perth

The following factors may contribute to Perth’s water scarcity issues:

A Changing Climate – I.e. The Climate Becoming Drier 

Australia as a country is already the driest continent in the world apart from Antarctica, but, Perth’s climate (as a State) is getting drier according to some reports.

Potential side effects of a drying climate might be declining rainfall, and increased likelihood of droughts.

We outline some of these effects individually below.

 

Annual Mean Temperature Anomaly Has Increased

Temperature has the ability to impact different aspects of the natural water cycle, and ultimately water supplies.

 

[Annual mean temperature anomaly has increased] 1℃ in southwest Western Australia in the past 40 years (theconversation.com)

 

Decreasing Rainfall/Precipitation Levels

On the yearly scale:

Perth’s annual rainfall has been declining by about 3mm per year on average (theconversation.com)

 

And, also on the decade, or multi decade scale:

Average rainfall levels have decreased in the past few decades (bbc.com)

[Perth’s] rainfall has declined almost 20 per cent since the 1970s … (abc.net.au)

 

Decreased rainfall means less water is naturally available to flow into water supply sources.

bbc.com mentions something similar to this: ‘Decreasing rainfall means less rain is flowing into dams and other water supply sources …’

 

Decreasing Rain Flowing Into Water Supply Sources

Decreased rain flowing into water sources can be due to less total rain, but also other factors (such as higher rates of evaporation as one example)

 

Some of the estimates of how much less water is flowing into Perth’s water sources compared to the past are:

[Only about …] 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)

… the amount of water flowing into [Perth’s] dams has fallen from an average of 300 billion litres a year to just 25 billion litres (abc.net.au)

 

theconversation.com indicates what the main causes of reduced inflows might be:

… inflows to water reservoirs are decreasing as a result of decreased rainfall and [decreased] river inflows

 

Rising Evaporation Rates

As we mentioned above, evaporation rates rising can be one of the factors that lead to less water flowing into water supply sources.

 

The overall effect [of rising evaporation rates 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

A city needs to have enough water supply capacity to meet the total consumption of the city.

There’s various factors that impact the consumption of the city, with population size being just one example, and consumption rates by the various industries and sectors being another example.

 

[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)

 

There’s Less Excess Water Running Off Into Some Storage Aquifers, & Reduction In Aquifer/Groundwater Recharge Rates Are Unknown

Aquifers are one supply source for freshwater.

However, less water running off into aquifers (caused by some of the factors outlined above), and slow aquifer recharge rates, mean that less water is available in the aquifers to withdraw.

 

According to theconversation.com:

Perth’s hydrology means that they can use their local natural sands and aquifers to store excess run-off from roads and roads.

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.

But, there’s been less excess water from winter rains.

Unlike dam inflows, … the full scale of the reduction in natural groundwater recharge rates [in currently unknown]

 

Perth’s Population Size vs It’s Water Consumption

A Growing Population 

A growing population can lead to increased water consumption.

However, in Perth’s case, water consumption rate (on a per capita basis) appears to have fallen despite a growing population.

Water restrictions and other water policy changes can impact per capita water consumption totals.  

It’s important to distinguish between long term water consumption trends, year to year trends, when analysing water consumption data.

 

Perth’s population grew by more than a third from roughly 2004 to 2014 (bbc.com)

 

From theguardian.com:

However, despite a rising population, Perth’s water demand was down by 8% [in 2013] compared with 2003. Water consumption has fallen from 191,000 litres to 131,000 litres per capita per year over the past decade in [Perth].

Perth’s consumption can be compared to San Diego’s consumption, [which] is an estimated 249,000 litres per capita per year 

 

San Diego has a population of 1.41 million compared to Perth’s 1.985 million, according to different online data.

 

Where Does The Majority Of Perth’s Water Supply Currently Come From?

Where Does Majority Of Perth’s Water Supply Come From?

Mostly desalination and ground water.

 

According to theconversation.com: ‘Perth now relies chiefly on groundwater and desalination rather than dams’

 

As of 2018, desalination provides almost half of Perth’s water needs while the other half comes from ground water (abc.net.au)

 

Why Do These Water Supply Sources Make Sense As Options Going Into The Future?

According to theconversation.com:

Although both [groundwater and desalination] 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

 

Where Other Australian Cities Get Their Water Supplies From

This resource is useful as it shows water supply of Australia’s major cities by water supply source (theconversation.com)

Perth’s major water supply sources are desalinated and ground water, with surface water and recycled water third and fourth.

Another city, Adelaide, gets additional water supply via transfer from another state’s water source (also known as transboundary water transfers).

So, we can see that different States in Australia get their water supply from different sources.

 

How Perth Is Addressing 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 passes through sandy soil for filtering first (or gets treated separately), and then gets mixed with groundwater in aquifers, before clean water is extracted for specific uses such as 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

These are wastewater treatment plants separate to the groundwater replenishment method.

 

From theguardian.com:

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 

 

Potable Water/Drinking Water Supplies

Desalination Plants

Some of the reports on how much water these desalination plants provide for Perth are:

 

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)

 

Other General Water Supply Solutions

Awareness, & Cultural/Social View Of Water

Perth citizens are being made aware that water is 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 on a per person basis. 

 

Backyard Bores

Some citizens in Perth have backyard bores … more than a quarter have them for watering their gardens.

These bores provide another water water source other than what’s supplied publicly.

 

Recycling Wastewater (& Re-using It)

Instead of dumping/discharging treated wast water into the ocean, it can be filtered to increase the quality of the water, and re-used.

 

Using The Natural Environment For Water Supply Processing

Such as natural sands for filtering and improving water quality, 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 and other natural sources of freshwater means a city can protect itself from variability in the natural water cycle and a changing climate.

 

Diversify Water Supply Sources

Relying on 2, 3 or more water supply sources makes a city’s water supplies less vulnerable to one point of failure.

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 there’s not a reliance 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 & Potential Penalties

Provide businesses with water management training, and the tools for data-gathering.

A certification scheme that allows them to promote themselves as water-conscious companies may also help.

Businesses and organisations that don’t meet requirements risk fines and will be ineligible for the recognition scheme.

According to some reports, 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

According to theguardian.com:

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)

 

Emphasise the importance of corporate social responsibility

For businesses and organisations to save water or use it efficiently.

 

Other water savings measures

– Using drains and ditches to channel water run-off into water storage areas

– Conserving water use particularly during summer – where it can be more of an issue

– Water restrictions on washing cars, using water on gardens, sprinklers

– Applying user pays water rates

– Metering of ground water users, like farmers and businesses, and monitoring for unproductive water use

– A problem that needs to be addressed is where water is in short supply, and water security tends to equal electoral security.

There is a conflict of interest here.

So, we need to remove the political conflict of interest from water supply … independence and guarantee of tenure are ways to do this for certain water supply positions and organisations

– Even though cities might solve some of their water scarcity issues long term, towns and rural areas need adequate support from state and national government too.

So, water supply solutions aimed at these areas is important – we can’t just neglect important towns and farming or rural regions within a state or province

 

Long Term Questions & Concerns With Perth’s Current Water Scarcity Solutions

There can be drawbacks and limitations to some of the solutions and water strategies listed in this guide.

Some of the potential concerns or drawbacks for desalination plants, recycling and re-using waste water, and other things implemented by Perth might include:

 

Desalination Plants

Some of the potential drawbacks of desalination plants might be that they:

 

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 standby by mode]

 

Can be energy intensive

On a per unit of fresh water generated basis

 

Can emit air pollutants and greenhouse gases 

This might especially be true if they use fossil fuels as an energy source.

Wind and solar energy may be cleaner – 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)

 

May cause increases in water rates/prices

Use of desalination plants may increase water bills for households because of the cost to run them, and the energy they use.

 

From theconversation.com:

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 

 

May damage the environment

With their discharge and waste by-products

 

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

i.e. they can give people a false sense that desalination plants are a long term solution for unlimited fresh water

This is not the case … desalination plants are not an unlimited sustainable source of water [at least with the technology that is available right now] for various reasons.

 

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

Recycling waste water and ground water replenishment may not be available everywhere 

These options can be location dependent, or, only available to cities with the expertise or money to finance them

For a city or town to use the sand filtering and groundwater replenishment method, they need sandy soil in the area that can naturally filter the wastewater, and aquifers that can store the water too.

Other cities could build dedicated wastewater recycling plants or treatment 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

Read more about the potential pros and cons of waste water recycling in this guide

 

Backyard Boreholes

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

 

In General

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.

The social, environmental and economic impact also have to be considered.

 

Treating, Recycling & Filtrating Water As Part Of A Long Term Strategy To Manage Water Scarcity

Several reports indicate these options might be some of the best options for managing water scarcity long term in Perth:

– Treating water at water treatment plants (waste-water, storm water, etc), and re-using it

Recycling water at water recycling plants, and re-using it

– Taking the treated wastewater that is currently dumped into the ocean (and wasted), and instead filtering it through Perth’s natural yellow sands. These sands help improve the quality of treated wastewater, and the water can be stored in the aquifers below the sand (essentially recharging the aquifers) until ready for use as non-potable water, irrigation, and for protecting wetlands and green spaces instead:

These options might be more sustainable or effective than desalination.

 

From abc.net.au:

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

 

From theconversation.com:

About 140 billion litres of treated wastewater are discharged into the ocean every year in the Perth-Peel region [and] A further 7 billion litres are infiltrated into the sands as a means of disposal where there isn’t an option for ocean outfall.

Investigations have … shown that the quality of treated wastewater [that is usually discharged into the ocean] can be greatly improved when infiltrated through the yellow sands into the limestone aquifer in the western part of Perth.

[The water] is suitable for [both] … public and private irrigation … after a few weeks’ residence within the aquifer.

Recent investigations of [the] land disposal sites have shown them to be effective in protecting wetlands from drying [and] … green spaces, which are needed needed to provide much-needed cooling … as Perth gets even hotter and drier … and [also] to safeguard … trees

 

According to theconversation.com, there might be additional sources of water that Perth could redirect into their existing storage aquifer that they currently aren’t utilising:

Perth’s hydrology means that they can use their local natural sands and aquifers to store excess run-off from roads and roads.

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]

 

Comparing Perth & Cape Town Water Scarcity Issues – Similarities & Differences

Perth and Cape Town have had both had to deal with water scarcity in different ways.

Some reports indicate their decision makers and water management authorities have dealt with the issue in different ways.

Some of the similarities and differences between these cities’ water issues might be:

 

Similarities

From abc.net.au:

[Perth faces] very similar climatic conditions to Cape Town 

Perth, much like Cape Town, was once almost entirely reliant on its dams

 

There’s … been significant population growth [in both Perth and Cape Town over the last few years to decades, and more population growth is expected] (theconversation.com)

 

Differences

From abc.net.au:

[Perth has] been in a position to make long-term decisions to deal with climate change [and Cape Town hasn’t]

[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

 

From theconversation.com:

Perth is half the size of Cape Town in terms of population …

Perth has progressively sourced more and more of its supply from desalination and from groundwater extraction, [while] Cape Town has not done this [yet]

 

Whilst Cape Town didn’t seriously invest in desalination prior to their last notable water crisis issue, some reports indicate they are now attempting to set up a number of small desalination plants to increase their water capacity/water supply per person

 

 

Sources

1. https://www.bbc.com/news/world-asia-27225396

2. https://theconversation.com/drought-proofing-perth-the-long-view-of-western-australian-water-36349

3. https://www.abc.net.au/news/2018-06-21/how-perth-dodged-its-own-water-crisis-like-day-zero-in-cape-town/9891472

4. https://www.theguardian.com/sustainable-business/2015/oct/06/perth-western-australia-drought-climate-change-water

5. https://theconversation.com/cape-town-is-almost-out-of-water-could-australian-cities-suffer-the-same-fate-90933

6. https://theconversation.com/is-perth-really-running-out-of-water-well-yes-and-no-90857

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