Northern Territory summary from water balances

For the Northern Territory, water balances have been prepared for six water management areas: the Darwin Water supply area, Goyder, Daly, Mereenie Sandstone, Roper, and Ti Tree. There are also water balances for four interjurisdictional areas that include areas in the Northern Territory; these are Ord River, Lake Eyre, Cooper Creek, and the Great Artesian Basin.

Uluru, Northern Territory, March 2006 Image by Robert Molloy

Key points

  • Rainfall conditions across many of these catchments were below the long term average values in the tropical north and much lower than average in the arid centre (although rainfall here tends to be episodic). Streamflows too were generally about average in the north, while there was generally no streamflow in the centre. In the Northern Territory, the only major surface water storage is the Darwin River Dam in the Darwin water supply area. It had about 25% less water in storage at the end of the 04-05 year than at the start. In the Mereenie Sandstone water management area there was significant mining of the groundwater resource resulting in a decrease in storage of over 9,000 ML.
  • Water use in the Northern Territory is generally from groundwater because in the absence of surface water storages in presents a reliable supply throughout the year. There were no water restrictions in the Northern Territory during 2004-05.
  • Much of the information in the water balances comes from estimates that were modified from NLWRA 2000. The exceptions being the Mereenie Sandstone water management area, which was based on the Alice Springs Draft Water Strategy and the Ti Tree water management area, which was based on the Ti Tree Region Water Resources Strategy 2002. Also for the Darwin water supply area and the Daly, information was sourced from groundwater modelling work currently being undertaken and previous water resource assessment work. Even so the reliability for many items in the water balances was low (i.e. ± 100%) mainly due to the scale of the water balance reporting.
  • Again, due to scale, the information on groundwater inflows and outflows in most catchments is generally of low reliability. In particular, there is little information available on groundwater storage volumes, groundwater use, groundwater-surface water interaction (particularly baseflow volumes) and groundwater discharged to evaporation across the management areas. For specific aquifers within some of the areas there is more reliable information available. This variability in accuracy has resulted in the average reliability index for the NT being ±80%.
  • While the low reliability of information for all items is problematic, it is probably suitable for the low level of use in most water management areas in the Northern Territory. In some areas of increasing development this issue has been recognised and more detailed planning and data collection necessary for the formulation of Water Allocation Plans is being undertaken.
  • Indications from stakeholders suggest that the water balances for the Northern Territory are of limited use because of the low level of pressure on the water resource and the data gaps and lack of data at the management area scale. For the water balance to be useful the scale of the balance needs to be matched to the level and intensity of use of the resource. Generally, the data required by the water balances were not readily available and they required assessment and collation of available data to make the data applicable to the management areas. At this scale also ET and runoff dominated the water balances and these are generally the components with the least level of information and reliability. The relatively low level of water use in these areas makes these components insignificant.

Further discussion of the water balances for Northern Territory is provided in the Water Availability National Perspective report, and the Regional Water Balances report, which are both available on the Publications page.

For individual results of water balance assessments go to Regional Water Resources Assessments

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Last Updated 30/05/2007