Case study 9 - Mining aquifers - Alice Springs Water Resource Strategy 2006-2015

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Background and geographic area

Alice Springs is a regional centre with a residential population of about 28,000. Most of the population lives within the Alice Springs Municipal Area.

The Alice Springs Water Resource Strategy covers a region of 8,200 square kilometres and includes a small number of communities and cattle stations (see Figure 1). Almost all of the water supplies in the strategy region are drawn from groundwater, either from alluvial sediments or from aquifers in the northern part of the Amadeus Basin. The Alice Springs Water Resource Strategy outlines the application of the principles outlined in the NWI Policy Guidelines for Water Planning and Management with regards to mining aquifers.

The map shows the Alice Springs Water Resource Strategy region

Figure 1: The Alice Springs Water Resource Strategy region

Objectives

The Alice Springs Water Resource Strategy was declared in September 2007 after more than two years of development and extensive community consultation. Seven key principles were developed by the community-based steering committee to guide the long-term implementation of the strategy. These were that:

  • the strategy should consider the needs of future generations through a conservative approach to water allocation
  • the strategy should encourage the advancement of best practice in water efficiency and the development of high value, creative and innovative uses for water
  • the strategy should deliver solutions to water management issues that are developed through a triple bottom line approach to balance economic, social and environmental needs
  • the strategy should be developed and managed through equitable community participation that maximises local determination
  • the strategy should be adaptive, encouraging reflective learning, improved knowledge and utilising accumulated experience
  • the strategy should maximise economic and social benefits of water extraction for the Alice Springs region and the Northern Territory
  • the strategy should be administered through efficient processes.

Application of a risk–based approach to management

Under section 22B of the Northern Territory's Water Act 1992, water allocation plans must allocate water within estimated sustainable yield to beneficial uses. Beneficial uses are defined in section 4(3) of the Act to include water for agriculture, aquaculture, public water supply, the environment, cultural uses, industry and for rural stock and domestic use.

Allocations to each of the beneficial use categories in the strategy are based on a working definition of 'sustainable yield' that is known as 'maximum allowable yield' this is the yield that protects environmental systems and preserves an acceptable amount of water for future generations so that no more than 5 per cent of flow shall be diverted at any time in any part of a river; total extraction from alluvial aquifers shall be based on estimated average recharge; and total extraction from the Amadeus Basin aquifers for a period of no less than 320 years shall not exceed 80 per cent of the total aquifer storage at the start of extraction.

The allocation of a majority of the groundwater in the Amadeus Basin aquifers to public water supply allows for increasing demand. Using the demand scenario adopted in the strategy, extraction for public water supply will need to be capped at 10,731 megalitres per year, which is the level of demand expected to be reached in 2017. Existing entitlements issued to the public authority responsible for water supply will necessarily be curtailed to maintain consistency with the strategy. As well as this amount allocated for public water supply, a component for both stock and domestic and other licensed use (such as agricultural use) has been allowed for. Other factors influencing the amount of groundwater available for extraction include changes in estimates of available storage as more hydrogeological evidence becomes available, improved extraction methods, water reuse and blending techniques, and reallocation of the amount available for horticulture at Rocky Hill. The planning policy for groundwater extraction from the Amadeus Basin aquifers is derived from the default policy for the Arid Zone of the Northern Territory. This policy states that total extraction over a period of no less than 100 years will not exceed 80 per cent of the total aquifer storage at the start of extraction.

As a result of the intensive consultation used to develop this strategy (ASWRS 2005, Community Consultation Report, NRETAS) , a more conservative approach than the default position was considered appropriate for Alice Springs. Therefore the policy is that, within the Alice Springs Water Resource Strategy region, current and future water extraction from the combined volume of Amadeus Basin aquifers must not exceed 80 per cent depletion of total available aquifer storage over a period of no less than 320 years or no more than 25% total storage over 100 years. This rate is equivalent to the maximum allowable yield and is used as the initial planning tool in developing this first strategy for Alice Springs (it defines extraction over the 10-year life of the strategy).

The maximum allowable yield adopted by this strategy (145,025 megalitres over 10 years) can be interpreted as depleting the total available aquifer storage by no more than 80 per cent over 320 years. However, it should be noted that the lifespan of the better quality water (less than 500 milligrams per litre of total dissolved solids) will be approximately half of that (160 years). Therefore it is desirable that good quality drinking water should be reserved for public water supply.

This strategy allows for some increase in demand for public water supply and development of the horticulture industry while limiting the extent of usage over the 10-year life of the strategy. It is not anticipated that these allocations will impose unacceptable constraints on either of these declared beneficial uses during the life of this strategy. Beyond the life of this strategy, the stated policy means that total extraction for public water supply cannot exceed the level of demand expected to be reached in 2017. Therefore, in the longer term, innovative methods of groundwater management will be required to provide opportunities for growth without exceeding the maximum allowable yield.

As part of improving groundwater management and improving water efficiency, and pursuant to its obligations under the strategy, the Department of Land Resource Management commissioned the Institute for Sustainable Futures to prepare the third and final report of the Alice Springs Water Efficiency Study1. This final report expands the suite of potential water efficiency and demand management options (first canvassed in the preliminary reports prepared by the Institute in 2003), which could be used in implementation of the strategy. In 2001 the Department of Land Resource Management appointed a full time water conservation officer who has been responsible for administering a Waterwise Schools and Waterwise Rebates program as well as promoting water conservation generally. The Department also hosts a Waterwise website2, encouraging water conservation and water efficiency generally within the community and to pursue the implementation of the findings of the study in the Alice Springs region. This is intended to have flow-on effects in helping the amount of water extracted for public water supply to remain within the cap as currently set out in the strategy.

Information requirements to achieve objectives

The consumptive pool is determined by the physical characteristics of the aquifer, the limits of current pumping technology and the amount of water remaining after environmental, cultural and other public benefit requirements are met. The consumptive pool, including public water supply, agriculture, industry and rural stock and domestic use, is determined within the remaining available water resource.

A water balance prepared at the time of the preparation of the strategy took into account the urban and rural development at that time. Future demand was also considered. The estimates of future demand used throughout the strategy were based on cumulative increase at the high growth forecast rate (1.5 per cent annual increase in water demand). At that rate, the life of the Roe Creek borefield, which currently provides drinking water for Alice Springs, is expected to last many decades. However, because of the drawdown of the Mereenie Aquifer System, the groundwater levels at the Roe Creek borefield will eventually fall to a depth at which it will become no longer economic to pump large amounts of water from that site. A future borefield site has been designated at Rocky Hill, approximately 25 kilometres from the Roe Creek borefield. The Rocky Hill borefield will continue to extract groundwater from the northern part of the Amadeus Basin, particularly from the Mereenie Aquifer System. The Northern Territory Government's current hydrogeological understanding of the aquifers associated with the Roe Creek area is far more advanced than its understanding of Rocky Hill. As a result, the environmental and cultural uses of water near Rocky Hill are yet to be determined, and further studies are required in the strategy work plan to assist in the determination of the extent and mechanisms of the water resource and what current non-consumptive demands exist for it.

Approach taken in dealing with uncertainty

The strategy sets the framework for a shared understanding between the government and the community of the resource, identifying opportunities and debating what may or may not be acceptable in the longer term. It provides an adaptive framework to amend allocations in light of new findings and improved understanding through ongoing research and a review process scheduled every five years. Adaptive management is based on accumulated experience, reflective learning and improved knowledge. For example, there is some possibility that water extraction from the shallower alluvial aquifers within the Alice Springs region could affect groundwater dependent ecosystems that are associated with the Town Basin, Inner Farm Basin, Outer Farm Basin and Wanngardi Basin. The potential for these ecosystems to be affected will be tested in close consultation with the Water Advisory Committee.

Forecasts of future demand for water must take into account projected population growth and the potential growth in water usage. Demand forecasting should also consider the impacts of natural or induced events such as climate change. It is estimated that increased temperatures due to global warming will be more pronounced in Central Australia than in coastal regions. Rainfall is expected to increase, but increased temperatures coupled with the existing variability in rainfall could result in greater evaporation and reduced runoff; this would result in reduced recharge to aquifers. Alternatively, more extreme rainfall events could produce more of the larger surface water flows, resulting in increased groundwater recharge in the strategy region. These climate change effects are not expected to be a major factor within the life of this strategy but should be considered in future revisions.

Approach taken in consulting with stakeholders

A ministerially appointed steering committee oversaw the development of this strategy. Public participation was an important part of the process. Community information, education and opinion have been crucial in creating acceptability and accountability in the search for the triple bottom line protecting environmental and cultural values while providing for existing and emerging industries.

The maximum allowable yield for the Alice Springs Water Resource Strategy region is based on the acceptable level of depletion of storage from the principal aquifers that support Alice Springs relative to economic and social benefit. The maximum allowable yield for the strategy region was determined through a comprehensive process of community engagement, which included several community forums, surveys, public submissions and the participation of a ministerially appointed steering committee of community stakeholders.

More information

More infomation, please visit: National Water Initiative