GROUNDWATER ABSTRACTION IN THE ROPER REGION - NORTHERN TERRITORY
Developing the North – groundwater and agriculture
S MacFarlane, C Fairfield
Publication Date (Web): 8 August 2017
When assessing the sustainability of water resources in the Roper region Tindall Limestone Aquifer (TLA), it is essential to balance the integrity of the environment, while maximising the potential of the available water resource. The TLA is one of the NT’s best-quality, highest-yielding, groundwater resources (DLRM, 2016). The current NT Government (NTG) is committed to continuing its water allocation planning to ensure on-going management of such resources (NTG – Draft Water Allocation Plan, 2011).
Legislation and planning regulations must reflect local use to mitigate wastage, and inappropriate use, of water. Water resources should be allocated among competing demands to meet socio-economic and cultural aspirations, minimise pollution, support ecosystems, and sustain industry including that producing food, protein, and energy. Water is allocated to end-uses based on current, and historic, information relating to the local availability of water: such data form the basis for water extraction licences.
In the NT, water planning is in its infancy. Water Allocation Planning for the TLA Mataranka began in 2008, with no WAP yet declared: to date, 19 groundwater licences appear on the Groundwater Extraction Licence register for the TLA Mataranka. Water licences give the NTG an independent mechanism with which to reduce water allocations as a result of reduced annual aquifer recharge.
Historical records of the Roper region TLA are sparse: the most current, comprehensive modelling report on the Roper River Catchment is the Gulf Water Study (Knapton, 2009). This karstic aquifer undergoes chemical weathering resulting in more permeable, cavernous, strata, to a depth of 150 m. Recent bore-drilling in the region has allowed a more accurate assessment of its water resources (Fig. 1).
Figure 1: The Roper River catchment and groundwater basins (Knapton, 2009)
Borehole standing water levels were used to identify geological formations and their permeability. With visual on-site inspection and an aerial survey (Fig. 2), borehole SWL data can confirm wetland/swamp areas: the prominent vegetation types are typical of paperbark and eucalypt woodland with palms (typically Livistona rigida). Here, a once-thriving environment has become waterlogged, resulting in a loss of vegetative cover.
Figure 2: Aerial photographs taken from 14° 58´ S, 133° 12´ E (c.15 km from Mataranka)
The intensification of agricultural production in Northern Australia provides opportunities for economic development. The National Water Commission conclude that only 5% of the 20% available water in the region was allocated (the 80:20 guideline used in the absence of a declared WAP, allows for 80% of aquifer water being left to the environment and 20% abstracted: WAP areas account for 160,005 km2, or 11.3%, of the NT) (NTG, 2011). As of October, 2016, there was an increase in the amount of water allocated in the TLA, although the increase in consumption has been minimal. Recent developments in the Mataranka area highlight the abundance of water available for abstraction from the TLA.
Borehole yields reached 130 l s-1, exceeding all prior modelled yield projections in the Mataranka region.
Water resources should be allocated equitably among competing demands to sustain the agricultural industry, produce more food, be energy efficient, minimise pollution, support ecosystems, and meet social and cultural aspirations.
A coupled understanding of the ground and surface water regimes in the TLA should be the focus of future research.
Data from borehole testing, accredited Bureau of Meteorology weather stations, river gauging stations, and soil testing can help to understand the TLA.
Further investigation of the annual recharge of the TLA is essential, with a focus on recharge via sinkholes.
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