The Victoria River District (VRD) is located about 500 km south
of Darwin in the north west of the Northern Territory.
The District is defined by a combination of environmental, legal
and social boundaries and is about 125,000 km2 in area,
which is almost twice the size of Tasmania. The VRD stretches from
the Joseph Bonaparte Gulf in the north to the Tanami Desert in the
south and from the Western Australian border to the Sturt
Plateau/Victoria River watershed in the east. Its environment is a
mix of grassy plains, rolling savannas, rocky spinifex country and
spectacular mesas and plateaux.
The VRD-Sturt region, like most of the tropical savannas, has a
tropical climate with hot, wet humid summers and sunny, warm, dry
winters (Bureau of Meteorology 1989). Situated south of the
Darwin-Kakadu area, only a small fraction of its north-western
boundary adjoins the Joseph Bonaparte Gulf and so this region comes
under very little coastal climatic influence.
Summer conditions are generally hot with average maximum
temperatures reaching 36oC. This region tends to be less
humid and less cloudy (Colls & Whitaker 1990) than the coastal
savanna regions. Thunderstorm activity, associated with north-west
monsoons, may occur on an average of 60 days but less frequently
— down to 20 days — towards the south.
Annual rainfall totals range from less than 600 mm in the south
to around twice that in the north (Bureau of Meteorology 1989).
Widespread heavy falls occur with the passage of tropical cyclones
which have more frequent effect in the north than the inland
southern regions (Gentilli 1972). Rainfall is moderately variable
from year to year and floods may result from particularly heavy or
persistent rain across the region's extensive river catchments.
Even though humidity, which averages between 30–70 per cent
in January and 20–60 per cent in July, is marginally lower
than more northerly coastal regions the higher temperatures
throughout the year produce more than 200 climate days of
discomfort (Colls & Whitaker 1990).
The dry winter is more prolonged than the wet season and is
dominated by the south-east trade winds. These winds pass across
nearly half the Australian continent to reach this region and so
lose much of their original moisture (Tapper & Hurry 1993).
This means that relative humidity is low, very little rain falls
and skies are clear. Temperatures are warm but wider-ranging than
in the summer or areas cloer to the coast with an average
minimum of about 12oC and no chances of frost. The
possibility of droughts occurring increases from moderate to high
in a southerly direction (Colls & Whitaker 1990).