Water usage in greater Darwin varies widely between the wet and dry seasons. During the dry season, the region typically uses 160 ML per day, while during the wet season this amount reduces to about 80 ML per day. Over half of the water consumed in the greater Darwin region is used in the residential sector (three-quarters of which is used outdoors), followed by non-residential commercial and government sectors. Household outdoor water use can increase as much as 10 times in the dry season. Annual water demand has grown at an average of 2.3 per cent over the 30 year period from 1980 to 2010. Variable annual rainfall and wet seasons frequently lead to annual fluctuations in demand of more than 10 per cent per year.
While most centres in the NT rely on groundwater, Darwin's main water supply is the Darwin River Dam. NT Power and Water Corporation currently extracts around 37 GL a year from the dam, and is licenced to extract 8.4 GL per year from the six production bores in the McMinns and Howard East borefields. However, operational constraints such as the need for routine maintenance mean that extraction from the borefields is usually limited to 6 GL per year, which is about 15 per cent of Darwin's annual supply.
The current Darwin Region Water Supply Strategy549 notes that NT Power and Water Corporation has undertaken water demand assessments based on a range of climate change scenarios, and has adopted a mid-range emissions scenario developed by CSIRO for its water supply planning. Modelling of this scenario suggests that there would be a significant impact on the yields available from the current Manton Dam and Darwin River Dam.
In the short term, NT Power and Water Corporation has designed demand-side actions under the five-year Living Water Smart program, which is aimed at helping the Darwin region reduce water use by 10 GL per year, or about a quarter of the current Darwin region water demand. Additional recycling opportunities are also being explored.
The NT Government has identified a number of priority water infrastructure projects that would secure long-term water supply for Darwin's growth and provide opportunity for growth in irrigated agriculture.
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549. Northern Territory Power and Water Corporation (2013)