IWRA Proceedings

Introduction
Water availability encompasses the physical reserves of water and also the accessibility, use and sharing of water. Varying socioeconomic and environmental conditions can greatly impact the vulnerability of a water system, with water availability playing a critical role in the future sustainability of a region1. The degree to which a water system is vulnerable is reflected in the (in)adequate provision of water supply in meeting demand within the system; this includes the vulnerability of water resource infrastructure to future climate change, population growth and industrial development6. Quantifying water vulnerability at the appropriate spatial scale provides key information for generating effective adaptation responses and coping mechanisms for impending changes in water resource availability2,4,5. An integrated water vulnerability index has the potential to result in more effective livelihood enhancement through addressing aspects of water scarcity, promoting equal development of livelihood assets, providing information for decision-making and enhancing disaster risk reduction strategies3.

This research integrates and builds upon existing concepts to develop a comprehensive framework and index to assess water vulnerability in one of Australia's most agriculturally productive regions; the Western Australian (WA) Wheatbelt. In this region of WA effective management of water resources is vital for (i) sustaining expanding populations, (ii) enabling livelihood diversification, and (iii) sustaining the economy of water-dependent industries (manufacturing, mining and agriculture). Through developing a water vulnerability index, water supply and demand vulnerabilities can be quantified. This enables identification of likely pressures on the water system, plus subsequent impacts on discrete components of supply and demand, to provide an evidence-base for informing policy to better manage water resources. In a wider context, vulnerabilities within the water system have relevance to future water-energy-food securities. In WA, this is particularly relevant as water assists in sustaining a large proportion of the economy and there is consistent competition for use between water, energy and food sectors. Consequently, this research explores the synergies and trade-offs for managing water supply and demand to enable increased sustainability within the water-energy-food nexus.

Methods
Water resources in the Wheatbelt are predominantly maintained through piped infrastructure (with source reservoirs external to the region) and rain-fed surface water bodies. Aquifers in the region, whilst extensive, are commonly too saline for agriculture and human consumption. Physical supply of water is also threatened by trends in declining precipitation and increasing temperatures. Coupled with a consistently increasing demand from water-dependent industries and population growth, there is a distinct threat to future water security for the region. An integrated water vulnerability index was developed to assess both demand-driven and supply-driven water vulnerability for the region; the index will allow for more informed water resource planning policy and will enhance preparedness through alleviating the impacts of future water accessibility issues. The index enables a quantification of vulnerability using 18 indicators (five supply, nine demand and four growth factors) which represent the region's overall water system. The index was spatially applied using a Geographic Information System (GIS) as an analysis tool, and incorporated multiple socioeconomic and environmental datasets. Water system vulnerability was assessed at quinquennial intervals from 1996 to 2011 at the statistical level area (SLA) administrative unit. Ordinary Least Squares (OLS) (backward stepwise) regression was used to determine which variables had the greatest influence on supply and demand vulnerability. The initial system framework was then conceptually expanded to pave the way for assessing vulnerability across the water-energy-food nexus.

Results and Discussion
Results indicate substantial spatiotemporal change in water vulnerability for the region. Water supply vulnerability is highest in the north-east region of the Wheatbelt where there is a high dependency on precipitation as a single water source. To the west, water supply vulnerability has generally changed relative to expansion of piped infrastructure. Water demand vulnerability is highest to the west where the greatest populations are located, particularly to the central and south-west. Overall, water system vulnerability is greatest in areas where water supply and demand vulnerabilities are respectively highest i.e. supply cannot meet demand for agriculture, industry and household consumption. OLS regression results indicate that water demand variables have a significant impact on overall system vulnerability. In particular, quinquennial growth factors in livestock and industry have a significant impact on water system vulnerability from one time period to the next. Additionally, climate has a significant impact on water system vulnerability, particularly in years where water availability is low due to below-average precipitation and above-average temperatures.

Conclusion
This research has provided a measurable and usable assessment of water vulnerability for the Wheatbelt, which will enable more informed water resources planning and management for the region. The concepts of the water vulnerability index will also be transferable to other water vulnerable regions with similar environmental and socioeconomic pressures. Consistent demand for water from the food sector (agriculture) and the energy sector (petroleum) in WA makes the water-energy-food nexus framework highly applicable to investigate sustainable outcomes for managing water more effectively. The next stage of this research is to expand analysis to incorporate supply and demand vulnerabilities in the food and energy sector to provide a holistic nexus framing for the Wheatbelt. This will allow synergies and trade-offs in water, energy and food vulnerability to be quantified and provide the potential to mitigate for projected changes, such as population growth or climate change. 1. Cohen, A. and Sullivan, C.A. (2010) Water and poverty in rural China: Developing an instrument to assess the multiple dimensions of water and poverty. Ecological Economics 69, 999-1009
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