The geography of the Goolwa to Wellington LAP Area

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.

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.

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 are an important attribute of the Goolwa to Wellington LAP area with the most prominant freshwater feature being Lake Alexandrina. The River Murray is the major river flowing into the lake, and enters the Northern end of the Lake near Wellington. When full, the Lake covers an area of 64,900 Hectares with an average depth of 2.8 metres. The Lake discharges into the Coorong and out the mouth of the River Murray near the town of Goolwa. Lake Alexandrina also recieves significant inflows from several Eastern Mount Lofty Ranges watercourses which flow through the Goolwa to Wellington LAP area to terminate on the Eastern and Northern margins of the Lake. These are the:

Prior to European settlement, the streams of the region had a gentle cross bed profile and were thickly vegetated with moderate channel definition. Land clearance, stock and introduced plant species together with changed flow rates have altered stream flow dynamics causing erosion and threatening built structures.

Lake Alexandrina and Albert along with the Coorong, form the Coorong and Lower Lakes Ramsar Wetlands of International Significance

The native vegetation of the area is largely governed by topography and climatic influences. The Mount Lofty Ranges support Mesmate Stingy Bark (Eucalyptus obliqua) and Brown Stringy Bark (Eucalyptus baxteri) woodlands in the higher rainfall locations of the ranges. These are typically comprised of a shrubby mid and understorey with some grassy areas. Occurring through the Finniss River and Tookayerta Creek Catchments are the Environmental Protection and Biodiversity Conservation (EPBC) Act listed Fleurieu Peninsula Swamps. These are permanent aquatic ecosystems whose vegetation community is only found on the Fleurieu Peninsula of South Australia.

As you head east from the ranges to the Eastern Mount Lofty Ranges foothills, the rainfall becomes more moderate and Stringy Bark forests give way to Blue gum (Eucalyptus leucoxylon), Pink Gum (Eucalyptus fasiculosa), Peppermint Box (Eucalyptus odorata) and Mallee Box (Eucalyptus porosa) grassy woodlands. These are often characterised by the presence of the local Sheoak (Allocasuarina verticillata) and have limited canopy structure. A key characteristic of these vegetation communities is the dominance of a grassy understorey, often hosting a myriad of lilies and orchids.

As you move further East onto the plains, the native vegetation becomes predominantly mallee vegetation communities. There are several types of mallee trees occurring in the local area including the Ridge Fruited Mallee (Eucalyptus incrassata), Red Mallee (Eucalyptus socialis) White Mallee (Eucalyptus gracilis), and the Slender leaf mallee (Eucalyptus leptophylla).

The vegetation fringing lakes Alexandrina and Albert is made up of several wetland vegetation communities and types including Swamp paperbark (Melaleuca halmaturorum), samphire (Halosarcia species), lignum (Muehlenbeckia florulenta), Typha (Typha domingensis), Juncus (several species), Schoenoplectus (several species), phragmities (Phragmites australis), and Gahnia (Gahnia filum). The occurrence and density of these vegetation communities and types is largely determined by degree and frequency of inundation, and quality of soil and water. In recent years some areas have declined significantly in health as a result of the receding water levels. In turn however, some plants such as phragmities have colonised new areas.

In the Mount Lofty Ranges, grazing along with recent rapid vineyard expansion are the main forms of land use. Up until the 1990’s, dairy production was the main land use however this has recently become a less significant land use is the area. Vegetable production, horses, remnant and revegetation, conservation parks and forests occupy large areas with rural living and limited cropping completing the scene.

On the plains, cropping and grazing is the dominant land use, although some land holdings are used for dairy, vines and vegetable production. Historically the main area for vineyards has been from south-east of Strathalbyn through Langhorne Creek to Milang. The scale of vineyard operations has expanded significantly in this 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, area averages more than $130 million of primary production per annum. The most significant commodities in that total are grapes, cereal crops, vegetables, livestock, wool, hay, and milk.

The total population of the Lakes and adjoining Ranges areas and towns is approximately 50,000 (ABS 2004). Population levels are increasing as many of the hills towns are now within commuting distance of Adelaide with the construction of the south-eastern freeway.

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 in relation to real estate prices. 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 across the area.

The traditional owners, the Ngarrindjeri, lands extend from Cape Jervis inland to Murray Bridge and south to Kingston including Lakes Alexandrina, Albert and the Coorong. Eighteen lakinyeri (clans) make up the Tendi and this is presided over by a Rupelle.

Before European settlement the Lakes and Coorong area supported many thousand Ngarrindjeri, in fact it was the most densely populated area of southern Australia. The Ngarrindjeri lands were made up of an ideal mix of river, freshwater lakes and seacoast. Each of the lakinyeri had custody of specific areas within the wider Ngarrindjeri nation.

Traditionally the Ngarrindjeri had a wide variety of food sources to choose from. (It has been estimated that they utilised almost 140 varieties including mammals, birds, fish, reptiles and plants.) They also dried meat, stored seeds, made seed cakes all for later use. As well, in the freshwater Lakes if they caught more fish than they could utilise at the time the excess were kept in impoundments for later use.

They had, in some areas, permanent “villages” comprised of dwellings that could house many people. People travelled within each lakinyeri’s area, residing during summer in camps near the water and during winter in camps inland.