4.9. Geology and Soils

The Lower Murrumbidgee occurs within a broader region known as the Murray Basin, a saucer-shaped region consisting of bedrock that has been filled with fluvial and marine sediments. The western part of the of the basin is known as the Mallee and the eastern part is known as the Riverine Plain. The majority of the Lower Murrumbidgee occurs within the Riverine Plain. Soil in this region occurs in three distinct layers, known as the Renmark, Calivil and Shepparton formations. These formations consist of sand, silt, and clay, and contain a number of groundwater aquifers.

Soil type varies greatly throughout the Lower Catchment:
• Solonised brown soils – prone to wind erosion – occur west and south-east of Balranald.
• Grey silty clay loams occur along ancestral stream and floodplain complexes in the Lowbidgee district and along the Murrumbidgee River.
• Grey, brown and red clays occur on the beds and floodplains of the Murrumbidgee River and associated creek systems.
• Red-brown earths occupy a large part of the eastern Riverine Plain, covering at least half of the Lower Murrumbidgee. These are moderately fertile and hold water well but are prone to erosion.
• Red earths occupy a small area in the north-east of the Lower Catchment. Nutrient-poor and prone to windsheeting and gullying.

References and Resources
• For more information, see CAP (1998), sections 8.1.9 and 8.1.10.

• NSW Government - Department of Natural Resources. Undated. New South Wales Natural Resource Atlas.