Salinity hazard in the Northern Territory has been assessed (Tickell 1994a, 1994b, 1997) by combining information on various physical parameters that contribute toward the likelihood of dryland salinity. These parameters were then combined in a simple additive model on a geographic information system to map zones of relative hazard.
The most obvious feature of the Northern Territory salinity hazard map is the absence of any areas classified as high hazard. Approximately 6% of the total area has a moderate hazard, 34% is classed as low hazard and 60% as very low.
The salinity hazard of the humid north and the south of the Northern Territory show distinctly different patterns: the humid zone is classified as mainly low and moderate hazard, whereas the arid zone is predominantly very low hazard; lesser areas of low hazard are restricted to the ranges.
Five indicators used in the hazard assessment were: groundwater salinity, vegetation, median annual rainfall, aquifer yield and the presence or absence of laterite. All were given equal weightings. Each indicator was divided into a range of values and assigned a numerical rating, with the most influential having the highest rating value. A salinity hazard index of a particular area was then computed by adding the rating for each of the five indicators.
The following findings are based on Tickell 1994.
- Overall salinity hazard for the Northern Territory is relatively low.
- The greatest potential for dryland salinity is in the inland semiarid areas (particularly on the Sturt Plateau) where conditions are marginally favourable and it would be expected to develop in isolated patches. Other susceptible areas are scattered mainly across the northern part of the Territory.
- If large areas of the Northern Territory were cleared for dryland agriculture, it is unlikely that dryland salinity would become the major problem that it is in southern and eastern Australia. This is because in higher rainfall areas, where deep rooted vegetation is abundant, salt storages in the ground are small.
- In the more arid areas, where salt storages are often large, deep rooted vegetation is either sparse or absent. Thus, clearing native vegetation in these areas would be unlikely to alter the water balance sufficiently to raise watertables to dangerously high levels.
- Groundwater monitoring of approximately 50 sites has shown no overall rising trends (Tickell pers. comm.)
Table of Contents for the Australian Dryland Salinity Assessment 2000
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