Climate
The climate is strongly influenced by topography and the ameliorating affects of the ocean.
Rainfall ranges from 900mm in the hills along the western edge of the ranges and tapers off to about 500mm on the eastern flanks of the Mount Lofty Ranges. Rainfall on the plains to the east drops to 300mm at the Murray River. The northern side of Lake Alexandrina is in the rain shadow of the Mount Lofty Ranges.
The climate is typically Mediterranean characterised by cool wet winters and hot dry summers. Average maximum daily temperatures range from 15C in winter to 25-27C in summer, although the weather is more moderate in the hills and near the coast. Frosts are common throughout the hills in the winter and early spring. Frosts are rare at the coast but occur on the plains.
Topography
The most pronounced features of the LAP area are the hills, plains, lakes and coastline.
The hills are over 350m above sea level to the west of the LAP and rise to 517m at Mount Barker in the north. The hills have steep slopes and broad flat valleys. The valleys typically have shallow to moderately deep acid-neutral, loamy sands to clay loams (with clay subsoils over basement rock) or acid-neutral sands over clay sub-soils.
The eastern plains slope from the base of the hills to the River Murray, Lakes Alexandrina and Albert and the sea. The eastern plains drop from 75-100m to sea level and are quite flat over most of the area. Their surface is made up of wind blown sand deposits.
Soils on the plains are generally sand or loams over clay becoming calcareous at depth, red to dark soils with clay at depth, or calcareous soils with shallow carbonate layers. South-east to north-west trending dunes of white, red or brown sand, overlay parts of the eastern plains. They are often low in fertility and non-wetting in nature. There are areas of deep loams and clay surface soils associated with the Angas-Bremer River systems near Langhorne Creek.
The area between Boggy Lake and Wellington is very low lying with portions inundated by the 1956 River Murray flood. Shallow water tables and the area’s soils contribute to it’s natural salinity with much of this area serving as a regional groundwater discharge area.
The lakeshores and Hindmarsh and Mundoo Islands form the third major feature of the topography. The shorelines are often high in silt and clay content and are integral to the region’s environmental importance, attracting a wide range of local and migratory aquatic birds.
The Sir Richard Peninsula on the western side of the Murray Mouth, like Younghusband Peninsula on the eastern side of the Murray Mouth, is an extensive coastal sand dune formation.
Hydrology
The nature of the major geological units dictates the availability and nature of groundwater supplies. In the hills aquifers in fractured rock formations have variable yields and quantities, depending on soils and rock type and the degree of fracturing, topography and climate.
Around Mount Compass sandy glacial deposits contain a considerable volume of water. The exact relationship between recharge, water use for irrigation and surface water flows in this area is unknown.
On the plains, the Mannum Formation in the Murray Group Limestone serves as an aquifer and has provided water of good quality and yield for the Langhorne Creek area where it has been used to irrigate vines, fruit trees, lucerne and vegetables.
A weak confining group generally caps the Murray Group, although it is ineffective to the south closer to Lake Alexandrina. The confined aquifer recharges along the escarpment and riverbeds, keeping salinities low, whilst further away from recharge areas salinities can be quite high. An overlying unconfined aquifer is generally saline with variable salinity levels.
Surface waters
Surface waters are an important attribute of the LAP area and are a feature of the landscape. The main catchments which all drain towards and into Lake Alexandrina are:
- Bremer River
- Barker River
- Angas River
- Finniss River
- Tooperang and Tookyerta Creeks
- Currency Creek
- Sandergrove Creek
Prior to European settlement, the streams of the region had a gentle cross bed profile and were thickly vegetated with no real defined channel. Land clearance, stock and introduced plant species together with changed flow rates have altered stream flow dynamics causing erosion and threatening built structures.
The LAP area included a large section of Lake Alexandrina, which forms part of the Coorong and Lower Lakes Ramsar Wetlands of International Significance.
Rural commodities and production
In the hills, grazing and dairy production along with recent rapid vineyard expansion are the main forms of land use. Vegetable production, horses, remnant and revegetation, parks and forests occupy large areas with rural living and limited cropping completing the scene.
On the plains, cropping is the dominant land use, although significant holdings are used for dairy , vines and vegetable production. Historically the main area for vineyards has been from south-east Strathalbyn through Langhorne Creek to Milang. The scale of vineyard operations has expanded significantly in the LAP area over the past 15 years. Intensive livestock industries such as piggeries and hatcheries occur too. Grazing is the predominant land use on Hindmarsh and Mundoo Islands.
Overall the LAP area averages more than $100 million of primary production per annum. The most significant commodities in that total are grapes, cereal crops, vegetables, livestock, wool, pasture for crops and hay and milk.
Mining operations occur in parts of the LAP area. Sand mining and limited moss rock removal occur in the hills. Salt and lime or gypsum are mined on the plains
Socio-economic factors
The total population of the LAP is approximately 40,000 (ABS 2004). Population levels are increasing as many of the hills town are now within commuting distance of Adelaide with the building of the south-eastern freeway.
The main towns are Strathalbyn, Mount Barker, Goolwa, Mount Compass, Nairne, Meadows, Callington, Kanmantoo, Macclesfield, Littlehampton, Milang, Langhorne Creek, port Elliot, Wellington, Ashbourne and Harrogate.
Growth has put increased pressure on land for housing, raising land prices and making it more difficult for agricultural enterprises to expand or justify the relatively low returns.
There has been an increase in road use, use of recreational facilities and a consequent increase in pollution and demands on waste and effluent disposal.
Events
