Gawler Uplands (Environmental Region 7.1)
This region consists of ten environmental associations. It is characterized by upland summits representing several old land surfaces, and extends from the Gawler Ranges eastward to include the plateau escarpments which form prominent land marks near Port Augusta. The Gawler Ranges represent an upland originating from an old land surface, the relics of which are visible as a bevelled summit plane sloping gently to the north. The predominent landforms are low flat-topped to broadly rounded hills, and gentle footslopes extending without a break into alluvial plains. Shallow loamy soils with much rock outcrop occur on the crests and upper slopes, with deeper red duplex soils on the plains. The vegetation on crests and upper slopes is usually sparse, consisting of spinifex and ephemeral grasses and herbs which provide good cover only after rain. The lower slopes carry woody vegetation, mainly low open black oak or myall woodland alternating with open mallee in the west. Saltbush vegetation is found on the plains, usually with a scatter of myall, bullockbush and false sandalwood; mallee box fringes several stream channels. The area between the Gawler Ranges and the eastern plateaux is formed by undulating plains with deep red calcreous earths, often covered with red aeolian sand, Small hilly areas are developed on sandstone in the north. Low open woodland of myall, or false sandalwood on deep soils, with an understory of bluebush and saltbush covered most of the plains. Mulgas occur on sandier soils. On the plateaux in the east shallow loams with frequent rock outcrops carry saltbush vegetation with low open black oak woodland on some escarpments. The footslopes which mainly represent pediments, are covered with colluvium which gives rise to red duplex soils. These are locally overlain by aeolian sand. Bluebush and saltbush species dominate the vegetation, but a sparse overstory of myall is usually present, giving way to mulga on sandier soils. Because of the contrast in landforms there is considerable variety in scenery within the region. Middleground panoramic views predominate on the plains. Hills, plateaux, and locally, ridges form backdrops for these views. Because the vegetation cover is sparse and rock outcrops are common on the slopes and crests the colour of these more distant landscape elements is strongly influenced by the red and purplish hues of soils and rocks. This is a significant characteristic of local foreground, perspective and enclosed views in the Gawler Ranges. Hill tops and ridges provide background panoramic views, which often include areas beyond their region. The climate is mild to hit in summer and cool to cold in winter with low and unreliable rainfall and high evaporation throughout the year. Mean annual rainfall ranges from 200 mm in the north-east to 300 mm in the south-west. Temperatures show considerable diurnal and seasonal variation. Mean monthly evaporation is very high in summer and exceeds the 90th percentile of monthly rainfall for every month. Mean annual evaporation varies from 2200 mm in the south-east to 2600 mm in the north.
