State of the Environment Report 2007
Western Australia's environment, economic productivity and the community's lifestyle and health all depend upon the availability of good quality fresh water. To provide these services, water needs to be extracted from waterways and groundwater aquifers. Careful management and use of water resources is necessary to ensure that ecosystems are sustained while delivering economic and social benefits.
The water supply sector aims to provide public and private users with a reliable water supply, both in quantity and quality, while safeguarding the needs of the environment. The sector is responsible for managing, protecting and allocating the use of surface water and groundwater resources in a sustainable manner for the benefit of current and future generations. This sector refers to water that is directly used for consumptive or productive purposes. While it does not extend to sewerage disposal, mine dewatering or agricultural surface drainage, it is recognised that these forms of water can be treated and reintroduced to the water supply chain for productive purposes.
As the State's population has grown so has demand for water, bringing with it the responsibility to manage this resource sustainably. The past decade has seen a continuation of reduced rainfall and increased population growth in the South West. These trends have placed unprecedented management pressures on the State's water resources. It has become clear that water managers must address the shift to a drier and warmer South West climate, rather than regard it as short-term drought. This requires the water sector to become more strategic in the way water resources are developed, protected, used and reused.
The State Sustainability Strategy outlines a vision for our natural resources by ensuring that they are '... conserved, protected, managed and used sustainably for the common good' (Government of Western Australia, 2003a, p. 108). The State Water Plan (Government of Western Australia, 2007c) has a vision of 'Our precious water resources are managed and developed in a sustainable manner to maintain and enhance our natural environment, cultural and spiritual values, our quality of life and the economic development of the State', and is supported by objectives that include:
This headline indicator represents an average of how sustainably WA's surface water and groundwater resources are being managed. In 1997, 36% (or 16 out of 44) of surface water management areas had at least one unit that was at, or exceeded, its allocation limit (most up to date information available). In 2006, 32% (or 12 out of 38) of groundwater management areas had at least one unit that was approaching or had exceeded its allocation limit.
This headline indicator summarises the water use efficiency of WA households. Sixty-four percent of the State's 116 water supply schemes met the State Water Strategy water use target of less than 155 kL a person per year in 2005-06. Although this target level was developed for Perth households, the target can be applied across the State as an interim measure.
This headline indicator summarises the household water use efficiency of Perth, the main area of drinking water consumption in the State. Consumption of scheme water in the Perth metropolitan area for 2005-06 was 151.4 kL per person. The target adopted in the State Water Strategy of less than 155 kL per person in a given year has been met since 2001-02. Annual water consumption per capita has decreased considerably in recent years, which may be attributed to intensive awareness campaigns and moderate sprinkler restrictions.
An estimated 2340 gigalitres (GL) of water was used in WA in 2005 (Government of Western Australia, 2007c), representing an increase of over 300% since 1980 (Figure TS8.1) and is still increasing. The State's population growth is one of the major drivers influencing water consumption. Climate change is also beginning to affect water supplies in the South West and increase water demand. Until the 1960s most of the State's drinking water came from surface water sources (rivers and creeks). Since the mid-1980s, groundwater has become the State's major water supply source. In 2005, this represented about 70% of total water use (Figure TS8.1).
![Figure TS8.1: Historical water use for Western Australia. [Courtesy of Department of the Premier and Cabinet]](/site/files/images/Figure-TS8.1_Large.jpg)
The Perth region has the highest water use in the State. Historic records from the Water Corporation show that water use per capita has generally increased since the 1940s until peaking in 1975 at 233 kL per person (Figure TS8.2). Consecutive dry years in the mid- to late-1970s prompted severe restrictions that dramatically reduced water consumption. Through the 1980s and 1990s, yearly water use ranged between 160-180 kL per person. This was further reduced in recent years to about 150-160 kL per person per year under the influence of the State Water Strategy.
![Figure TS8.2: Per capita water demand for households in the Perth Integrated Water Supply System. [Courtesy of Department of the Premier and Cabinet]](/site/files/images/Figure-TS8.2_Large.jpg)
About three-quarters of the State's water resources are used by the private sector, primarily for agriculture, mining, industry and services (Figure TS8.3). The largest water users are from the irrigated agriculture (40%) and mining (24%) sectors. In comparison, households use only 18%. Nearly two-thirds of total surface water extracted from waterways is used by irrigated agriculture (65%). The major users of groundwater are mining (35%) and irrigated agriculture (25%).
![Figure TS8.3: Total water use by Western Australian user group, 1999–2000. [Data source: Department of Water.]](/site/files/images/Figure-TS8.3_Large.jpg)
Water is a valuable resource and efforts to recycle and reuse water (in appropriate circumstances) are being encouraged. The State Water Strategy set a target of 20% of treated wastewater to be recycled by 2012 (Government of Western Australia, 2003b). On average, about 12% of the State's treated wastewater is currently recycled. Regional communities currently reuse about 40% of all municipal wastewater due to limited supplies of freshwater and the high cost of alternative supplies. In Perth, only 5% of treated wastewater is being recycled (see 'Human settlements').
The new Department of Water is responsible for determining the sustainability of water resources. This involves determining how much water can be taken for consumptive use without significant risk to ecological systems. Ecological water requirements are determined from scientific investigations and modelling. Environmental water provisions take into account the ecological, social and economic context. This information is used to derive the sustainable yield and set the allocation limit for consumptive use (Department of Water, 2006).
In 2006, about 30% of groundwater management areas and groundwater management units were close to full allocation or over-allocated (Table TS8.1). Of all management areas and management units, 13% and 11% respectively were over-allocated (exceeded their allocation limit and deemed to be unsustainable), (Table TS8.1). Groundwater management plans, some of which incorporate preliminary environmental water provisions, exist for 21% of heavily allocated groundwater areas (see 'Altered water regimes').
Current information for surface water allocation is not available and presents difficulties in managing the resource sustainably. In 1997, about 36% of surface water management areas in the State had at least one management unit that was at full allocation or over-allocated. At the smaller management unit scale, one-quarter of those units were at or exceeding the estimated sustainable yield (Table TS8.2). Surface water management plans, containing detailed environmental water provisions, exist for 12% of heavily allocated surface water areas, namely the Harvey River and the Ord River (see 'Altered water regimes').
Surface water in the South West is allocated to public and private users to various extents (Figure TS8.4). Under most pressure are surface water resources in the Harvey River Basin, which is nearing 100% of the allocation limit, and surface water resources in the Swan Coastal and Murray basins, which have reached more than 80% of sustainable yield. The use of surface waters in other parts of the South West is comparatively small and remains largely unmanaged, and there is significant additional water demand in the Collie and Denmark basins.
![Figure TS8.4: Surface water allocation status in the South West. [Courtesy of Department of Water. Cited in McFarlane (2005). Note: The size of the circles represents the relative volume of the surface water resources. Only allocations >1% of the estimate sustainable yield displayed in the pie charts.]](/site/files/images/Figure-TS8.4_Large.jpg)
![Figure TS8.5: Groundwater allocation status in the South West. [Courtesy of Department of Water. Cited in McFarlane (2005). Note: The size of the circles represents the relative volume of the groundwater resources. Only allocations >1% of the estimate sustainable yield displayed in the pie charts.]](/site/files/images/Figure-TS8.5_Large.jpg)
With the exception of the Perth North Basin, groundwater in the South West is mostly allocated to private users (Figure TS8.5). Groundwater use is highest for the Perth North, Perth South, Bunbury and Busselton-Capel basins, with allocations typically exceeding 50% of sustainable yield. Groundwater in the Perth North Basin (including the Gnangara Mound) is under the most pressure, exceeding 100% sustainable yield, and environmental damage has been documented on the Gnangara and Jandakot mounds. Other groundwater basins in the South West remain largely unallocated, although there is significant additional groundwater demand in the Bunbury, Busselton-Capel and Augusta basins.
Some areas of the South West utilise a large proportion of their allocated limits (Figure TS8.6). While the majority of groundwater areas along the coast remain within allocation limits, there is evidence of over allocation in many areas. In the Gingin, Perth North, Busselton-Capel and Collie basins, up to 10% of management units are over-allocated.
There are 139 water supply sources in the State that need to be protected to a high standard to provide drinking water (Government of Western Australia 2003a). Protecting water at the beginning of the supply system minimises the risk of contamination and reduces the amount and cost of treatment. Management consistent with the Australian Drinking Water Guidelines (NHMRC & ARMCANZ, 1996; NHMC & NRMMC, 2003) helps ensure that water supplies are protected. An important element of protection is the recognition of public drinking water source areas and the preparation of drinking water source protection plans (Table TS8.3). These plans focus on the characteristics of individual catchments so that suitable land use controls can be established and pollution risks and other issues addressed. As of June 2006, plans had been completed for 41% of water source areas requiring a protection plan. While the number of plans completed is gradually rising, the number of newly developed water supply sources has also increased marginally.
Water conservation means using water more efficiently (see 'Water use in settlements'). The State Water Strategy set a yearly target level of consumption of 155 kL/person for Perth domestic scheme consumers (Government of Western Australia, 2003b). This target has been met since 2001-02 and is largely attributed to rebates on water conservation and efficiency products, awareness campaigns and sprinkler restrictions. Although the target was not designed for regional water supply schemes, their performance against the target shows that 64% of schemes achieved the target in 2005-06 (Table TS8.4).
Industry has also played a leading role in the conservation of potable water supplies by sourcing other alternative water supplies. For example, Alcoa has developed a strategic water conservation program that achieved a 20% reduction in potable water use from 2001 to 2005. Between 1996 and 2001, BP's Kwinana Refinery achieved a 25% reduction in total water use and an 82% reduction in drinking water use. Swan Brewery saved about 60 ML per year of potable water by implementing recycling initiatives and Wesfarmers CSBP had reduced its industrial use of potable water by about 440 ML per year (Chamber of Commerce and Industry, 2002).
Water use in WA has tripled over the last 25 years, and may double again over the next 20 years. This is caused mainly by growth in private supply for irrigated agriculture and mining, and a steady growth in demand for public water supplies as the city of Perth and regional centres continue to grow (Figure TS8.1). The Perth region has already outgrown its readily available water resources (Figure TS8.7) and its continued growth will place water supplies in neighbouring regions under more pressure (e.g. Preston and Peel regions). The biggest growth is expected in the Perth-Moore regions (due to urban use and irrigation), the East Kimberley (due to Ord Stage 2 irrigated agriculture), Preston (due to urban growth and manufacturing industry) and the Goldfields (expansion of gold and nickel mining). Additional demand for water resources will place more pressure on infrastructure and the environment. In some areas water from natural sources may be insufficient to meet demand and alternative supplies may be costly, limiting economic development.
![Figure TS8.7: Projected South West water demand scenarios. [Courtesy of Department of Water. Cited in McFarlane (2005).]](/site/files/images/Figure-TS8.7_Large.jpg)
Inappropriate catchment management may lead to biological or chemical contamination of potable water supplies. Salinisation, eutrophication and erosion are considered significant threats to urban, industrial and agricultural water supplies. For example, more than one-third (36%) of waterways in the South West have become brackish or saline and are no longer fit to be used for drinking water (Government of Western Australia, 2000). A further 16% is of marginal quality. In terms of eutrophication, there is also evidence of some regional water supplies becoming impacted by nitrate plumes originating from horticultural practices (Water Corporation, unpublished). In terms of erosion, Lake Argyle (the State's largest water supply dam on the Ord River) has been heavily impacted by sedimentation, with more than 10% of the dam's capacity being filled by eroded sediment from the catchment over the last three decades (Government of Western Australia, 1998a).
A projected rise in temperature across the State of several degrees Centigrade is likely in this century in line with global projections. This is expected to be accompanied by further significant decrease in rainfall over the South West. The actual outcomes are dependent on global action on limiting greenhouse gas emissions over coming decades and these cannot be predicted. However, it is expected that climate change will place water supplies under significant pressure (Indian Ocean Climate Initiative, 2005b). The South West has already experienced a 10-20% decline in rainfall over the last 30 years, caused by a sudden climate shift in the mid-1970s (Indian Ocean Climate Initiative, 2002 & 2005a). This has subsequently reduced surface runoff of water into dams by an average of 50% (Figure TS8.8; Government of Western Australia, 2007c) and reduced water infiltration to groundwater aquifers. Future changes to climate will have significant implications for the determination of sustainable yields for surface and groundwater resources, the allocation of water resources to consumers, and infrastructure development.
![Figure TS8.8: Streamflows to Perth’s public water supply dams since 1911. [Courtesy of Department of the Premier and Cabinet.]](/site/files/images/Figure-TS8.8_Large.jpg)
In 1996, Western Australian government institutions for water services and water resource management were separated in line with national water reform policy. While this may have assisted in removing conflicts of interest between water service providers and resource managers, and improved the efficiency of water service provision, it did not benefit water resource management to the same degree. Previously, WA was a national leader in water resource assessment and management, but these institutional changes diluted and weakened the State Government's water resource management expertise. Part of the reason for the decline was a 33% reduction in funding over the period 1998-2003 for core water resource management operations which include water resource investigation, assessment, planning, licensing and regulation. There is also a severe deficiency of information for private water use (i.e. mining, industry, agriculture and household bore use). A review of State water resource management in 2003 (Auditor General for Western Australia, 2003) identified significant deficiencies in most water resource management functions and some major challenges now facing water management. A new Department of Water has been formed to address these deficiencies.
State Water Strategy and State Water Plan: The State Water Strategy (Government of Western Australia 2003a) was released largely in response to drought conditions. It outlined means of improving water use efficiency, recycling, research and innovation and community understanding of the real value of water. A State Water Plan (Government of Western Australia, 2007c) was recently released to build on the strategy and outlines the policy direction for the sustainable management of water resources, including the development of regional water plans, strategic water issue plans and statutory water management plans.
Water reform: As part of the State Water Strategy, the State Government undertook a review of irrigation activities in WA (Government of Western Australia, 2005). The review made a series of wide ranging recommendations with implications for the way water resources were planned, allocated, managed and monitored. The government also signed the National Water Initiative in 2006, which required further water sector reform. The Blueprint for Water Reform in WA (Government of Western Australia, 2006) provides recommendations for development of statutory water management plans, water access entitlements, metering, water resource management charges, water use efficiency, integration of land and water planning. A Government response document (Government of Western Australia, 2007a) outlines a number of actions to implement water reform.
National Water Initiative: In April 2006 WA became party to this Commonwealth program that recognises the imperative to ensure the health of groundwater and river systems, ensure environmentally sustainable levels of extraction, increase the productivity and efficiency of water use and secure water supply services. It builds on the 1994 National Water Initiative (Council of Australian Governments, 1994) where greater attention was made to ensure adequate environmental water provisions are set when sustainable water allocation limits are assessed. Western Australia has since developed a draft implementation plan (Government of Western Australia, 2007b). The plan will be underpinned by reform of water legislation and will focus on water access entitlements, the planning process for setting allocations, water entitlement trading, metering and water pricing.
Water use efficiency: Water use efficiency measures for public water supplies were developed through the Perth's Water Future Report (Stokes et al., 1995) and then enhanced through the State Water Strategy. Highly successful components were sprinkler restrictions and the suite of Waterwise programs for householders and industry, including the State Government's rebate scheme for efficient household appliances. A total of 5.5 GL per year had been saved through the Waterwise program since 2003 (Kobelke, 2007). It has been extended on-farm with an education and training program for irrigators and farmers, coordinated by the Department of Agriculture. The program has also been extended to plumbers, garden centres, land developers, garden irrigators and schools. There has not been an equivalent education program to improve the water efficiency of private users. CSIRO is undertaking several research programs including the development of models that better utilise technology for water allocation, storage, treatment and reuse in relation to sustainability principles.
Water reuse: Increasingly, wastewater, stormwater and rainwater are being seen as recyclable water alternatives, rather than as disposal problems. Only about 5% of treated wastewater in the Perth city region is being recycled. To increase this figure the Water Corporation is focussing on four key categories of water recycling schemes for Perth: reuse, public open space irrigation, agricultural irrigation and scheme water augmentation. Comparatively, wastewater reuse in regional settlements is much greater.
Water quality protection: Protecting the quality of water resources in public drinking water source areas is important. There are currently some 80 public drinking water sources in the State that lack a protection plan. As the plans can affect what landowners can do on their land, considerable public consultation is required. Once proclaimed, they are used in planning decisions at the State and local government levels.
Desalinisation: the State's first desalinisation plant to be used as a major public water supply was officially opened in April 2007. It produces 45 GL/year at full production, which is currently ~17% of the annual demand from the Integrated Water Supply Scheme; including the Goldfields and agricultural region serviced by the Water Corporation. To reduce environmental impacts, electricity for the plant has been sourced from the Emu Downs Wind Farm.
Managed aquifer recharge: is the infiltration or injection of water into an aquifer for immediate or deferred use. There is a number of research projects currently underway using treated wastewater. In January 2007 the Water Corporation announced plans for a $38 million four-year groundwater replenishment trial in the Leederville aquifer. The Water Corporation would undertake this trial with the intention of implementing a full scale system to deliver 27 GL/y of public drinking water by 2015.
The State's growing population and its mining, industrial and agricultural sectors are dependent on adequate water supplies. While sustainable management and use of the State's water resources is essential, it is becoming increasingly difficult to achieve alongside optimal economic growth. As the community seeks to become more involved in water resources management, it will also become essential that quality information on the State's water resources is readily available. The health of our inland waters depends on adequate water flows and groundwater levels. The building of dams and bores to abstract water can directly impact and erode environmental and social values. It will be critical to determine environmental water provisions for all water resources to prevent this from happening. Water licence holders are seeking to enhance the value of water entitlements through greater security of water allocations (based on a share of the available water) and increased ability to trade them. Adopting more secure water entitlements needs to be balanced with the potential for increased risks to the environment and other users.
New sources of water are needed to meet demand across the State. The key challenge facing water planners is the ongoing impact of changing climatic conditions that may affect the amount of water available from various source options. For example, in response to consecutive dry years in the late 1990s, the State Government accelerated development of its water supplies, including recent construction of Stirling Dam on the Harvey River and the Kwinana seawater desalinisation plant. Other potential water source options including extracting water from the South West Yarragadee groundwater aquifer and transporting water from the Kimberley have been investigated. Without reliable sources of water, consumers face uncertain water supplies.
9.29 Develop and implement regional water strategies and statutory water management plans for priority areas.
9.30 Review water pricing structures to better reflect the true costs of water resource management. These costs should be passed on to all public and private consumers responsible for current consumption levels.
9.31 Promote water recycling and efficiency measures to allow for more to be done with the same volume of water, matching water quality to water use, and rationalisation of source development impacts on water dependent ecosystems.
9.32 Develop an appropriate and effective balance of water source options to maintain security of supply, while minimising environmental impacts in a changing climate.
Carnarvon (population approximately 10 000) stands at the mouth of the Gascoyne River. The town's population and industry are totally dependent on river flow events for water supply. The river's unique hydrology is such that river flow almost instantly recharges groundwater. The groundwater supports a wide range of crops including bananas, citrus fruit, stone fruit and many different vegetables. It also supports native riparian vegetation, mainly river red gums and coolabah trees, along the lower Gascoyne River.
Water management areas (Basin A) in the lower Gascoyne River support mostly horticulture. Water management areas further upstream (basins B to L) support the Water Corporation's well field, which supplies scheme water to households and industries in the town. When the Gascoyne River stops flowing and river recharge to groundwater ceases, groundwater in Basin A can still be pumped for irrigation. However, excessive pumping may produce prolonged periods of drawdown that can cause salt water to move into freshwater areas, making the water unsuitable for irrigation, human consumption and riparian vegetation.
Following an 18-month period of no river flow in 1994, maximum groundwater drawdown levels ranged from 3.25 m to 10.30 m below the ground surface. Trees remained healthy during this time. However, excessive exposure to saline groundwater could have lead to death of fringing vegetation along the river. In 2002, the former Water and Rivers Commission (now Department of Water) worked with the Carnarvon community to produce a strategy that ensured optimised water use, provided drought security and enabled key environmental goals to be met. Several agreed management actions were:
It is expected that these management actions will ensure a greater reliability of water supply during times of no river flow and prolonged drought, and protect the native vegetation along the lower Gascoyne River. Groundwater use in this area has proven to be very efficient. Carnarvon's productivity to usage ratio is one of the highest in the State (around $4000/ML) compared to other areas (around $2000/ML).
