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EnviroNorth > VRD-Sturt > Landscape and Climate

Landscape and climate

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.

Tropical climate

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

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

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).

Winter

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).