The region includes metropolitan Adelaide and its adjacent countryside, and broadly corresponds with the Australian Bureau of Statistics' Statistical Divisions of Adelaide and Outer Adelaide. In 1981, the region had 79% of the State's population, with 69% - 882,520 people - in urban Adelaide. Despite its urban emphasis, the region produced 20% of the value of South Australian farm output in 1981. The output was more diverse than in any other region. Only 30% of it was the traditional mix of wheat, barley, and sheep for meat and wool. The poultry industry accounted for 13% and dairying another 9%. The other commodities included vines, fruit, vegetables, potatoes, meat cattle, pigs and hay.
Cities have strong effects on their surrounding countrysides. They encourage diverse and intensive rural production; make heavy demands for stone, sand and clay; and require the collection and storage of water and the disposal of wastes. City people use their countrysides for some of their sports and recreations. Many enjoy visiting the remnants of native vegetation and wilderness. Others like to live in the country and travel to work in the city.
With its varied terrain and rock types, its moderate to high rainfall and its lengthy waterfrontages of sea-coast, lake and river, the Adelaide Region can satisfy a wide range of human needs within a compact area. But not all of those needs are compatible. Conflicts between competing land-uses and between farmers, developers and conservationists can be intense.
The region has three broad topographical divisions: the western plains and basins, the Mount Lofty Ranges, and the Murray Plains in the east. A traveller from the sea-coast to the River Murray sees strong changes of landscape, as indicated in the false-colour imagery of the satellite picture of the central part of the region. Annual average rainfall ranges from 350mm on the extreme north-west and on the Murray Plains, to between 1000 mm and 1200 mm on the highest parts of the Ranges.
North of the city, broad plains of pasture and farmland are traversed by the Light and Gawler rivers. Around Two Wells, Gawler and Virginia underground water is pumped to provide spray irrigation for significant areas of market gardening.
Southward, the coastal plain narrows until the hills meet the sea in low cliffs. Most of the triangular area of the Adelaide Plains is occupied by the metropolitan area. Its eastward growth has been constructed by the decision to limit urban development on and beyond the abrupt face of the Mount Lofty Ranges, but suburbs extend north-east to Elizabeth and Smithfield and south-west into the Noarlunga Basin. The Willunga Basin, south of the River Onkaparinga, is essentially rural, containing the important red wine producing vineyards of McLaren Vale. Most of Australia's almonds grow on the alluvial fans at the foot of the Willunga Scarp.
The Mount Lofty Ranges form the core of the region. They consist of intensely folded and faulted sedimentary and igneous rocks of Cambrian and Precambrian age. Some of the major topographic breaks on the west and east of the Ranges represent north-south trending faults. Southward, in the Fleurieu Peninsula, the Ranges form an undulating plateau with spectacular coastal cliffs. In the north the broad Barossa Valley cuts across the line of the Ranges. Summit heights of about 500 metres are typical, with Mount Lofty the highest at 727 metres. Relief, rainfall and soil vary greatly and are reflected in the very diverse land-uses. There are conservation parks and forest reserves. Outside them, the remaining native vegetation consists of scattered eucalypts standing in sheep and dairy pastures, and patches of dense eucalypts on steep slopes and poor soils. The Woods and Forests Department has planted some 10,000 hectares of pine forest at Mount Crawford, Kuitpo and Second Valley, and there are 1200 hectares of pine around the metropolitan reservoirs.
The central portion of the Ranges, known as the Adelaide Hills, supports a combination of land-uses which is rare for the fringes of an Australian city. Competing and sometimes incompatible activities include water harvesting and storage for farm and city; dairying; sheep grazing; apple, pear and cherry orchards; vegetable and potato growing; horse breeding; and quarrying. Recent urban-based 'overspill' activities include dog-boarding kennels, horse-riding schools and stables, plant nurseries, hobby farms and rural retreats.
The water harvesting function of the Adelaide Hills makes the region unique in Australia. Other large cities have been able to draw most of their water-supplies from forested catchments which were of such low agricultural potential that they were reserved for the water-supply authorities a century ago. In the Mount Lofty Ranges, where most of the land was alienated to farmers in the early years of settlement, the catchments are now the homes of some 20,000 people and tens of thousands of sheep, cattle, pigs and horses. In an attempt to arrest deterioration in the quality of water flowing into the Hills reservoirs, more stringent controls have been applied since the mid-1970s on land subdivision and the citing of intensive animal-producing facilities, such as piggeries, feed lots and poultry farms.
The eastern fringe of the Adelaide Region is much drier and the landscape generally more open than in the Ranges. The transition from a timbered landscape with lush pastures and numerous farm dams to starker hills and plains is often abrupt. It is seen quite dramatically in the eastward descent from Mount Marker on the South Eastern Freeway, and between Tungkillo and Palmer on the road from Adelaide to Mannum. Yet the diversity which marks the entire Adelaide Region is still present. There are citrus orchards at Mypolonga, dairying along the River Murray flats, vineyards on the lower Bremer River at Langhorne Creek, and mixed grain and livestock farming on the Angas Plains near Strathalbyn and between Mannum and Sedan. Surviving patches of the mallee scrub, which a century ago covered most of the Murray Pains, are preserved in small conservation parks south of Monarto. Intensive planting on the former 'new town' site of Monarto has recently restored a vigorous tree cover to a bare countryside.
Outside urban Adelaide the largest settlements are Gawler (population 9433), Murray Bridge (8664), Victor Harbor (4522) and Mount Barker (4190). These towns have a component of daily commuters who work in the metropolitan area, but they are also important local service centres. Along the south coast, between Rosetta Head and Goolwa, urban development is now almost continuous. Victor Harbor had long been the fashionable summer resort for Adelaide residents. With mass car ownership the coast has become popular with day-trippers, second-home owners and caravaners. Many people now retire there. The eastern coast of the Fleurieu Peninsula from Sellicks Beach to Cape Jervis is increasingly popular for day trips and short holidays.
The long history of the Adelaide Region has left a generous heritage of small country towns, many with buildings of considerable charm. Lobethal and Hahndorf were established in the 1840s by German immigrants who set up 'street village' settlements with long narrow holdings extending back from the street frontages. Such villages were common in the east German homeland, but rare in Australia. Hahndorf promotes its German heritage and its traditional events, such as the mid-summer Schuetzenfest, attract tens of thousands of visitors. Lobethal, somewhat less accessible, is noted for its Onkaparinga Woollen Mills which developed from a small weaving concern established in an old brewery in 1872.
Strathalbyn (population 1756) and Willunga (667), at the eastern and western flanks of the South Mount Lofty Ranges, are towns with notable stone buildings. Strathalbyn was settled by Scottish immigrants in 1839. Willunga, surveyed in the 1840s, was originally a centre for slate quarrying but is today the centre of the almond industry.