The climate of the Goolwa to Wellington LAP area is strongly influenced by topography and the ameliorating effects of the ocean.

Rainfall ranges from 900mm in the Mount Lofty Ranges along the western edge of the Goolwa to Wellington LAP area and tapers off to 500mm on the eastern flanks of the Ranges. Rainfall on the plains to the east of the ranges declines to approximately 350mm at the Murray River near Wellington.

The northern side of Lakes Alexandrina and Albert is in the rain shadow of the Mount Lofty Ranges and receives in the order of 400mm annual average rainfall. The southern part of Lakes Alexandrina and Albert receive higher rainfall due to the influence of coastal weather patterns.

The weather is usually more moderate in the hills and near the coast, with temperatures frequently 5 to 10 degrees cooler than those in Adelaide. 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 Mount Lofty Ranges to the west of Lake Alexandrina are over 350m above sea level and rise to 517m at Mount Barker. 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 subsoils.

The plains to the east of the ranges and around the lakes 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 elevation above sea level to sea level and are quite flat over most of the area. Their surface is often 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 its 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 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.