Rivers - Assessment of River Condition - Northern Territory
Northern Territory River Assessment
Assessment Results
The Northern Territory covers 1,346,200 km2, has a coastline of 6,200 km, and comprises 17.5 percent of the total area of Australia. The Territory has two distinct climatic seasons - the wet season from November to March when Darwin has an average annual rainfall of 1500 mm, and the dry season when rainfall is only 25 mm. Topographic features of the Northern Territory include: the high rocky Arnhem Land Plateau; the Tanami Desert which extends into Western Australia; and the Simpson Desert which extends into Queensland and South Australia.
The biological assessment of Western Australian rivers showed approximately 88% of the river length assessed in the Northern Territory was in reference condition. However, only 11% of the total river length had been assessed. The environmental assessment found that 77% of the assessed river length was largely unmodified, and the rest in moderately modified condition. This degradation was attributed to catchment disturbance and changes to the physical habitat.
Fifty seven percent of the river length assessed had disturbed catchments, with degradation largely attributable to land use activities. There has been no significant change to the hydrological regime of the assessed river length in the Northern Territory.
Riverine physical habitat has been altered in 37% of the river length assessed in the Northern Territory. Changes to the riparian vegetation (41% modified) contributed the most to altered physical habitat though it should be noted that the bedload condition was not determined in the Northern Territory.
A water quality index was not determined in the Northern Territory.
Comparison of the Biota Index and the Environment Index
Ideally, scores for the two main indices would be similar for each basin. In general, the Biota Index does not demonstrate the same degree of degradation as the Environment Index. Reasons for this may include:
- macroinvertebrates may be insensitive to some environmental changes, including large-scale changes (e.g. changes in connectivity and catchment disturbance), and to changes in some riverine habitat components (e.g. changes in salinity). Other biota, such as streamside and aquatic plants, algae, fish or water birds, in addition to invertebrates would give a more comprehensive assessment of the cumulative effects of environmental change.
- there may be lags between environmental degradation and biotic condition (e.g. nutrient or sediment loads to streams); or
- an environmental component that would explain a biotic response was not measured (e.g. a toxicant).
Environment Index scores compared to Biota Index scores for all basins.
Further Information
- A key point of contact for river management in the Northern Territory is the Department of Lands, Planning and Environment. Information on the NT Waterwatch program can be found at www.lpe.nt.gov.au/care/waterwatch/default.htm
- Exit to more information on the AUSRIVAS for an introduction, models, taxonomy and downloads.
- Assessment of River Condition: and audit of the ecological condition of Australian rivers (by R. Norris, I. Prosser, B. Young, P. Liston, N. Bauer, N. Davies, F. Dyer, S. Linke, and M. Thoms)(PDF 4418 KB)
- View the Audit's Australian Catchment, River and Estuary Assessment 2002
- View the Audit's Australian Agriculture Assessment 2001
- Link to Data Library to download data and metadata
- Link to the Map Maker to make a map using this information.
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