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Adapting to climate change for water resource management: Issues for northern Australia

Rural conditions Climate change Water Australia Northern Territory Queensland Western Australia

There are two aims of this work focused across northern Australia (north of the tropic of Capricorn). First is to identify adaptive strategies to deal with climate change in each jurisdiction. Second the work identifies issues for adaptation in water resource management across the region in light of potential impacts and local conditions.

Over half of Australia‘s annual runoff occurs in the north Australian region from November to April. The region is relatively undeveloped and sparsely populated compared to southern Australia. Almost 30% of the land base is owned under Indigenous tenure. Drought and over-allocation of water resources in southern Australia has focused attention on the potential for expanding irrigated agriculture in the north. With an outlook for increased drought in southern Australia the pressure to look north is likely to increase. While rainfall projections in northern Australia are identified as stable to increasing, our research highlights that the outlook for water availability remains uncertain under climate change scenarios across the north.

Work by CSIRO and BOM (2007a) and CSIRO (2009a) predict that to 2030 and 2070, northern Australia is likely to experience hotter temperatures, more intense rainfall and more intense cyclonic events. It must be stated that climate change impacts are likely to vary across the region and impacts may be highly localized. There may be an increased risk of saltwater inundation and erosion in coastal areas. While inland areas may experience more extreme high temperatures, drought, flooding, dust storms and bushfires (CSIRO, 2009a; Green, 2006). Although northern Australia produces over half of Australia‘s runoff, it is considered to be water limited for two main reasons. First there is high evaporation and evapotranspiration for most of the year (CSIRO, 2009a). Second the potential for water storages is constrained (NAWLT, 2009; Petheram et al, 2008). There may be consequences for water resources from climate change (as well as infrastructure) which combined with increased population growth (especially in Darwin, NT) could make water stress more acute, particularly during the dry season. As water stress increases the need for a robust and adaptive framework to manage water becomes more important. Climate models may allow policy makers to anticipate particular events in setting design standards for water infrastructure (Hallegatte, 2009).

Reference has been made in water plans to climate change in each jurisdiction. There is also recognition in climate adaptation strategies that water resources will be impacted by climate change. Adaptation for water resource managers and policy makers is not new. But the effects from climate change may impose new and perhaps unforeseen challenges on water management regimes. This is particularly true across tropical northern Australia, a region already difficult to manage and deliver services to because of its size, remoteness and relatively poor infrastructure base. It is recommended in literature that adaptation for water resources should consider basins in an integrated way and address issues such as flood and drought protection, managing water demand, and maintaining and protecting infrastructure. Water markets are a demand side strategy to adapt to climate change. Markets have enabled irrigators in southern Australia the flexibility to cope with drought and maintain productivity during water shortages. Water markets may enable adaptation to the effects of climate change by allowing re-allocation among users and flexibility to users through trading. Markets can also encourage water use efficiency which is important where climate change reduces water availability. The use of water markets are at a formative stage across the north Australian region, with little to no trading at the time of writing. Despite no trading, northern jurisdictions generally allow water trading to occur in areas subject to a water plan (competition for water tends to be higher in these areas and necessitates a plan).

Water plans seek to identify a sustainable level of consumptive extraction by using best available science and community consultation to support economic, ecological and social outcomes. It is acknowledged across the north that data relating to water resources and climate is limited. This is particularly true for groundwater resources for which there is a strong reliance across much of the north. There is considerable risk for the extraction on groundwater resources on groundwater dependent ecosystems, and on the customary values of Indigenous Australians. The Northern Territory has in place one water allocation plan in the region, the Tindall aquifer plan. Queensland has the Gulf and Mitchell resource operation plans. Western Australia has the Ord River water management plan. The Tindall plan in the NT is the only groundwater plan completed in the region. In Queensland and the NT plans are enshrined in statute and last 10 years (though in the NT the plan is reviewed within 5 years). While in WA the Ord plan is for 3 years.

An important tool for adapting to climate change in water plans is the ability to reduce water allocations to entitlement holders in line with reductions in water availability. This is often done according to the level of security provided to an entitlement holder (high, medium and low security). The economic value of entitlements is linked to its level of security. In the Northern Territory, the Tindall aquifer water allocation plan provides that all water licenses may have their allocation reduced to zero in serious drought (commencing with low then up to high security). In times of critical water shortage the Water Controller in the NT has the power to impose restrictions on stock and domestic use as well. In the Ord there is greater security afforded to users because of the storage capacity in Lake Argyle (101 GL). Allocations in the Ord are determined based on water storage levels in the dam, and restrictions can be imposed on allocations if water reaches  ̳critical levels‘. It is expected that in only 5 years out of every 100 will water reach  ̳critical levels‘ and allocations be reduced. Hence entitlement holders will get their full allocation 95% of the time. Plans are reviewed and new information may be integrated and entitlements amended to reflect any changes in water availability.

Most work on climate change and hydrology research has been focused on metropolitan centres in WA and Queensland. There has been relatively little work across the north to understand the effect of climate change on water resources. Uncertainty and lack of knowledge serve to constrain planning efforts. Adapting to climate change in water resource management requires an integrated approach, coordinating efforts across government and collaborating with stakeholders to be effective- it will be important to to support socio-economic outcomes over the long term. The impacts from climate change will not be distributed equitably and will have implications for Indigenous groups (who are disadvantaged), with consequences for health, wellbeing and livelihoods (Green, 2006). Industry will be affected by the impacts of climate change in northern Australia. For example, the pastoral industry which covers almost 90% of land use could be negatively affected by reduced feed quality and water availability. These impacts can be mitigated by proactive planning, as well as collaborative and stakeholder focused planning activities. Planning will require particular effort to include and engage Indigenous groups, where consultation efforts have in the past fallen short of expectations in water management.

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