Our future in : Securing Gnangara groundwater and adapting to climate change

May 2018

Page 1 Securing Gnangara groundwater and adapting to climate change

Over the years, south-west has become hotter and drier due to climate change. It’s common knowledge that this means less inflow to dams, but it also means less recharge to groundwater. Being located on one of Australia’s best groundwater resources has allowed Perth to become a modern, vibrant and green city that provides a lifestyle we all enjoy. Now, with reduced rainfall and significant use, the groundwater system has shifted out of balance and our once healthy system is under strain.

The Gnangara groundwater system is a basin of water-holding sands and gravels interspersed with clays. It underlies Perth between the hills and the coast and the area from the Swan River to Gingin Brook. We abstract this water and use it for parks, ovals, gardens, agriculture and drinking water. It also supports the health of our natural environment.

Our community, local governments and the Water Corporation have taken steps to respond to a drying climate by being more efficient and seeking alternative supplies. However, more is needed if we are to rebalance the system as a whole.

The Department of Water and Environmental Regulation as the state government responsible for managing the state’s water resources is now working with water users to prepare the next Gnangara groundwater allocation plan.

This brochure shows that by working together and rethinking how we interact with water, we can secure our groundwater in a drying climate to help create a liveable, sustainable, productive and resilient Perth for the long term. We can achieve this by reducing groundwater use, replenishing (or ‘recharging’) the and introducing other sources such as recycled water.

Page 2 Rebalancing the system means we can continue to have groundwater for communities, industry and the environment in a drying climate.

Securing Gnangara groundwater and In balance Out of balance Rebalanced adapting to climate change

Rainfall 600 mm Rainfall Abstraction Abstraction Rainfall Abstraction

1970s 2030

Restoring the balance: Gnangara groundwater 1970s 2030

Gnangara plan area map

Page 3 Our most precious resource Stretching over 2200 square kilometres under the Swan coastal plain, the Gnangara system is Perth’s lowest cost and largest source of good quality water. It is a crucial component of Perth’s drinking water supply (Integrated Water Supply Scheme, operated by the Water Corporation). The Gnangara system provides almost half of all the water used in the Perth metropolitan area each year. It supplies water for agriculture, parks, ovals and gardens, and water for Perth’s scheme supply - distributed by the Water Corporation. Gnangara groundwater also supports environmental features such as lakes, wetlands and deep rooted vegetation. Pine plantation Banksia trees Beenyup Swan Rural wastewater Valley In the Gnangara system, deeper water is Horticulture treatment up to 35 000 years old and the geological plant structure is much older (up to 175 million Wetlands years old). The system is made of many Urban layers of sand, sediment and clay. Pores between the sand hold water, which mostly comes from winter rainfall making its way Ocean Super cial down through the soil to recharge the Saltwater interface aquifers. The system contains three main aquifers.

Groundwater is a shared resource. The shallow Superficial aquifer, known as the , is mostly Saltwater interface used by local governments, schools, industry, farmers and households that take (offshore) water from bores. Some is used for Perth’s Con ning layer scheme supply which also sources water from dams, desalinisation and recycling. The deeper Leederville and Yarragadee aquifers are mostly used for scheme water supply.

The Jandakot groundwater system, south of the Swan River, is a similar but smaller Groundwater ow system that is also used by local water Saltwater interface users and for scheme water supply. (offshore) Darling Fault

Page 4 Pine plantation Banksia trees Beenyup Swan Rural wastewater Valley Horticulture treatment plant Wetlands Urban

Ocean Super cial aquifer Saltwater interface

Leederville aquifer Saltwater interface (offshore) Con ning layer

Yarragadee aquifer

Saltwater interface Groundwater ow (offshore) Darling Fault

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The Gnangara groundwater system has three main aquifers and supports Perth’s water supplies, wetlands and vegetation How is Gnangara groundwater used?

Gnangara groundwater supports households, businesses, parks and gardens, through about 2600 water licences to take groundwater and 70 000 domestic bores.

Perth’s scheme water Domestic garden bores Gnangara groundwater provides at least We estimate 70 000 individual households 110 billion litres or 110 gigalitres (GL) a year for take about 36 GL a year through domestic Perth’s scheme water supplied by the Water bores to irrigate gardens and for use by Corporation (enough water to meet the needs livestock (exempt from water licensing). of over 800 000 people).

Horticulture and viticulture Pine plantations Horticulturalists and farmers take more than Pine plantations intercept rainfall and reduce 60 GL of groundwater a year to irrigate or prevent recharge to groundwater. locally grown vegetables and fruit.

Public open space Gnangara groundwater is Perth’s lowest cost water source and the economic Local councils, schools and sporting clubs take benefits have been estimated at a total about 45 GL a year to irrigate parks, sports net present value of$6.7 billion1, which is ovals and other public open spaces. equivalent to about $400 million a year.

Commercial purposes Local businesses and other commercial industries take over 10 GL a year to irrigate grounds or to use in production of goods and services, such as construction.

200 How much water is used from Legend 180 the Gnangara groundwater Domestic garden bores Local, self supply system? 160 Public supply (Water Corporation) 140 In 2016–17, about 287 GL was allocated from the Gnangara system – enough water to fill 120 Optus Stadium 287 times or 114 800 Olympic swimming pools. 100

Over 40 per cent of this went into the Water 80

Corporation’s Integrated Water Supply Scheme, Superficial Billion litres per year and about 45 per cent was used for local parks 60 and grounds, horticulture and businesses. 40 About 13 per cent was taken by householders for gardens using domestic bores. 20 Yarragadee Leederville 0 Aquifer

Page 6 What else does Gnangara groundwater support?

Without groundwater we wouldn’t have the lakes, wetlands, green parks, bush and trees that make Perth such an enjoyable place to live.

Protects water quality Helps create our sense of place Leaving enough water in the ground helps Lakes, wetlands, vegetation and cave systems reduce impacts between water users. It also that depend on groundwater help support rare protects water quality by preventing saltwater species, create our ‘sense of place’, link closely from moving into the aquifer from the sea with cultural values and make our communities and river, and by not exposing acid-forming soils. cooler and more attractive places in which to live.

Supports lakes and wetlands Many people have made significant investments so they can live near and enjoy Our natural lakes and iconic wetlands on the wetlands, bushland and trees. The presence Gnangara Mound depend on groundwater of wetlands adds to home values by about to survive. $4 billion across Perth, and native vegetation on the Gnangara Mound is valued at $100 million1. Supports vegetation Some of the bushland and large trees in our communities and parks tap into groundwater 1 Marsden Jacob Associates 2012, Assessing to survive our hot, dry summers. the value of groundwater, Waterlines report, National Water Commission, Canberra

Provides storage capacity The storage capacity of aquifers is utilised through managed aquifer recharge to store water for later use and this can boost water levels.

Page 7 A system out of balance

Rainfall, streamflow and recharge to High groundwater use and lower rainfall have groundwater have been declining across resulted in declining groundwater levels and south-west Western Australia since the drying of wetlands and vegetation. 1970’s. Most of our rain falls in winter and this is when groundwater is recharged, so when In 2016–17 water levels at 16 out of 30 there is less winter rain there is less recharge representative wetland and vegetation sites to groundwater. were lower than the criteria levels set by the Minister for the Environment to protect When we developed the 2009 Gnangara the groundwater system and dependent groundwater allocation plan, average annual ecosystems. rainfall was 729 mm ( rainfall site 1975–2008). Since then we’ve had two of A system out of balance also puts water the driest years on record: 483 mm in 2010 quality at risk in some locations. Enough and 578 mm in 2015. Between now and 2030, groundwater needs to flow out to the river we expect an average of between 650 mm and coast to prevent saltwater intrusion into and 700 mm with dry years occurring aquifers. Saline water has already moved inland more often. in the Superficial aquifer in some places. If we act together to rebalance the system, we The rapid reduction in rainfall and can adjust to changes in rainfall, increase water security and reduce adverse impacts on water recharge has been faster than users and the environment. reductions to groundwater use and has shifted the groundwater system out of balance.

2006 2015

Rebalancing the groundwater system would help recover wetlands that have dried up because of declining groundwater levels, such as Loch McNess, near .

Page 8 What can we do to secure our groundwater future?

To maintain groundwater as a viable resource for ongoing use and other public and environmental benefits, we need to Our goal is… stabilise groundwater levels and enable To rebalance the some key areas to recover. Gnangara groundwater There are many ways to do this. To help achieve a better balance, some local system by 2030 to secure our governments and businesses are already investing in water-efficient technology, lowest cost and most accessible investigating managed aquifer recharge water source for Perth and and applying water-sensitive urban design. to support a healthy New urban developments can also be an opportunity to promote alternative, local environment. water supply solutions that are fit-for purpose, especially for public open space.

All water users will need to consider options like these and use water more efficiently to adjust to reduced groundwater availability.

Strategies to rebalance Gnangara groundwater in a drying climate by 2030

Sustainable Water efficiency Alternative sources groundwater and innovation

• Reduce groundwater • Improve water-use • Reduce reliance on abstraction. efficiency to reduce groundwater by using water demand. fit-for-purpose alternatives. • Increase recharge through planned land-use changes. • Enhance urban design to • Increase groundwater reduce demand and increase replenishment and managed • Use science and research recharge. aquifer recharge in the best to find the best solutions locations. for each location.

We can achieve this by working together Share information, work together and form partnerships to build capacity and find water solutions.

Page 9 Sustainable groundwater Exciting finds in science

Groundwater will continue to be an important One of the goals of Department of Water part of Perth’s water supplies because it and Environmental Regulation’s $7 million is our lowest cost and most accessible Perth Region Confined Aquifer Capacity water source. project was to see whether we could Reduced abstraction is part of the solution optimise the way we take and use water if we are to adjust to less rainfall by 2030. from the Gnangara system, including new In some locations, even with initiatives such locations to draw water from deep aquifers as increased efficiency, reducing water that have less impact on the system. licence entitlements is one of a number of measures that will be considered. The recently completed four-year study, Groundwater abstraction for scheme supply including research from Curtin University – which was higher as an interim response to and the University of Western Australia, low inflow to dams – was reduced when the adds to our recently updated groundwater Southern Seawater Desalination Plant began model to help our task. production in 2013. The Water Corporation has also been taking less from environmentally The study started with several data sensitive areas and moving abstraction deeper collection programs that covered over to the confined parts of the Leederville and 7000 square kilometres of the Perth region, Yarragadee aquifers. As a result, water levels have started to stabilise in some areas of the using geophysical equipment mounted Gnangara Mound. to planes and helicopters. More detailed investigative work followed, including The Department of Water and Environmental seismic surveys, drilling groundwater Regulation is now working with both the Water Corporation and self-supply water monitoring bores up to 900 metres deep, users to plan future changes, including and processing geophysical data using reductions to abstraction, by 2030. The the Magnus Cray supercomputer at the approach may vary locally depending on Pawsey centre. how much the area is out of balance and what is practical and achievable. Today, the Department of Water and Environmental Regulation and the Land-use change such as urban expansion Water Corporation are using the new and removing some of the pines from the model to assess the best locations for Gnangara Mound will improve recharge to reinjecting recycled water to help recharge groundwater, which will reduce the effects the system. of lower rainfall in some places. Enhancing recharge and protecting public drinking water sources will remain an important consideration of any land use changes.

Science and research play an important role in solving emerging water problems. Department of Water and Environmental Regulation is currently analysing the latest scientific data alongside practical advice from Gnangara water users to work out where, when and how best we can bring use and recharge back into balance. Once we have agreed on a pathway forward, it will be mapped out in the next Gnangara groundwater allocation plan and staged over the next decade.

Page 10

Liveable cities with less water

The City of Wanneroo and the Department of Water and Enviromental Regulation have developed a strategy so that the limited groundwater in the 9000-hectare north-west urban growth corridor in Perth can be shared between public water supply and the irrigation of parks, gardens and recreational areas. The City of Nedlands, in partnership with the Department of Water and Environmental Regulation and the University of Western Australia, has studied water-saving technologies to see which are most cost effective and practical to implement for public open space.

Water Households are helping save groundwater by being more waterwise in their home and efficiency gardens. Waterwise gardens include native and drought-tolerant plants, mulching, and and innovation efficient, well-maintained irrigation systems. One of the great side benefits of these Efficiency and innovation will practices is the simple fact that they be key to making Gnangara groundwater save money. stretch further and be more sustainable as a resource. Waterwise garden bore owners that use water efficiently not only give their garden Reducing demand through efficiency: the right amount of water it needs but they • increases productivity help share groundwater locally. Garden bores in urban and semi-rural areas collectively use • minimises water costs 20 per cent of the Superficial aquifer. Staying within sprinkler rosters and avoiding over-use • avoids or delays the need for new helps reduce impacts on neighbours and the water sources. local area. Many water users have already adjusted Some have become their water use and good examples of this agricultural businesses very efficient through contemporary are occurring across Perth. technologies, irrigation schedules, improved Through the Waterwise Council Program, maintenance and better management. more local councils are becoming more The combination of crop types, crop areas water efficient, improving turf maintenance and the type of irrigation systems used can practices and adopting new irrigation and also boost water efficiency. water monitoring technologies. Leaders in water efficiency and innovation Some developers, schools and businesses are showing that we can all adjust to a are also succeeding through water-sensitive drying climate by rethinking how we use urban design. Good design is essential for water wisely. reducing water use as well as for managing stormwater and enhancing recharge. Page 11 Alternative sources

Over time, introducing alternative water sources will take pressure off Gnangara groundwater and build climate resilience for businesses and the community.

The Water Corporation already has two desalination plants, which can provide up to 50 per cent of the metropolitan area’s scheme water needs. Desalination has given us a secure water source for part of Perth’s drinking water supply that doesn’t depend on the rain.

Other ways to boost supplies include:

Groundwater replenishment where large volumes of highly treated recycled water are recharged back into deep aquifers to augment our drinking water. Perth’s first full-scale Groundwater Replenishment Scheme at the Smarter solutions for recycled water Beenyup facility in Craigie has been completed with a capacity to recharge 14 GL of recycled The City of Kalamunda is recycling water into groundwater for storage and winter drainage water, storing it abstraction each year. Planning is underway to double the scheme’s capacity to recharge through managed aquifer recharge, and 28 GL each year. using it to irrigate parks in summer.

Managed aquifer recharge where water In response to reduced groundwater is infiltrated back into an aquifer through availability and local salinity issues, the reinjection bores or ponds, basins and trenches Western Suburbs Regional Organisation for later use or to benefit the environment. of Councils is investigating new ways Well considered location and design will deliver benefits for local water users and the of using recycled water to irrigate environment. parks and public open space either directly from the Subiaco treatment Stormwater harvesting where rainfall runoff plant or by ‘topping up’ the Superficial is captured in tanks or other storages as a aquifer for reuse later. water source that can improve water supply for non-drinking purposes in households or The Department of Water and businesses and parks and gardens. Good urban design can enhance stormwater recharge to Environmental Regulation is also groundwater – a natural form of stormwater partnering with the Department harvesting. of Communities, the City of Swan and developers to consider water Wastewater treatment and reuse where supply options for the Department of wastewater is recycled to be used for irrigation of parks, public gardens and golf Communities’ Brabham subdivision in courses, and potentially other uses such as Perth’s north-east. horticulture and industry.

The best alternative, non-potable supply may vary from place to place, and interested water users will need to carefully assess the range of options available and the costs and benefits of each.

Page 12 Page 13Page 13 Working together Gnangara groundwater: what’s the plan? We at the Department of Water and Environmental Regulation have the state government All water users have a part to play responsibility for managing the state’s water in adapting groundwater use to the resources and how they are used. drying climate. We can all contribute To make sure we have Gnangara groundwater for now and the future, we have begun working on by rethinking how we use, manage the next Gnangara groundwater allocation plan, consulting with the Water Corporation and water and interact with water in our homes users to find practical pathways to bring the and businesses. system back into balance by 2030. This will be a challenge. We will help in any way we can by promoting innovative water projects, Better water outcomes are also more achievable if building capacity in water efficiency, sharing we work together. There are great examples of this research and exploring new water supply options across different industries and some of these have with water users. been touched on throughout this brochure. To help guide the rebalancing, we will set new limits The Waterwise Council Program, developed by the on groundwater availability as part of the next Department of Water and Environmental Regulation allocation plan. This may also include changes to and the Water Corporation, has built a cooperative how we license groundwater. working relationship with local governments resulting in improved water use efficiency within What ‘rebalanced’ looks like will be developed council facilities, public open space and within the through the planning process over the next year. communities. The partners are continuing to improve We will focus on achieving a productive and this program for better groundwater outcomes. sustainable groundwater supply and a healthy environment in the face of an ever-drying climate. The Department of Water and Environmental Regulation is a participant in the Cooperative In developing the plan, we will work with water Research Centre for Water Sensitive Cities, which users to identify how to phase in new solutions and is researching how water management can support minimise impacts on people and businesses. cities to be sustainable, resilient, productive and livable. All of the research is available online, We are also taking a longer view. Our parallel work including a vision for Perth as a water sensitive city. on Perth and Peel Water @ 3.5 million is assessing watersensitivecities.org.au the water demand outlook and considering the water supply strategies to meet water needs, particularly non-potable water needs, for a city growing to 3.5 million people by around 2050.c

Page 14 Page 15 Have your say

If you have questions or comments, would like to be involved in the conversation or receive updates on the next Gnangara groundwater allocation plan, please email [email protected]

We expect to have the new Gnangara groundwater allocation plan ready for public comment by the end of 2018. During the public comment period anyone can make a submission on the plan. All licensees will be notified at the start of the public comment period and it will be advertised in state and local newspapers, on our main website

dwer.wa.gov.au and at gnangara.dwer.wa.gov.au

You can also follow us on:

@DWER_WA

#Gnangaragroundwater

This publication is available at our website dwer.wa.gov.au or for those with special needs it can be made available in alternative formats such as audio, large print, or Braille.

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Phone: 6364 7600

Fax: 6364 7601

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