Soil/Landform Unit 156

Swamps and waterbodies are prominent along the western boundary of the catchment. Many of these swamps in recent season have been dry and productive.

Area:

13 580 ha

1.02% of CMA region

Across the dissected basalt plains of the Western Plains are numerous swamps and closed depressions that host a wide variety of flora and fauna. These swamps have been derived on

Quaternary

basalt,

alluvial

clay, sand and gravels and tend to be associated within two regions of the Western Plains. The reasoning for this is not entirely understood, but it would appear there is a high correlation of swamps with certain basalt flows. Most of the land has been cleared where these swamps were, or have been developed with drainage to remove excess surface water. Remnant vegetation classes on these plains include plains Sedgy Wetland, Stony Rises Herb-rich Woodland and Aquatic Herbland / Plains Sedgy Wetland Mosaic. Land use is mainly restricted to grazing owing to the waterlogged state of soils in most years, however cropping is quite productive when annual rainfall is below average. Soils include the grey cracking clays on the lava plains and black cracking clays associated with swamps and depressions of the stoney rises. While waterlogging is the major limitation, soil

compaction

may also be a limitation for production without adequately controlled traffic.

The cracking clays provide valuable soil moisture and nutrients that have resulted in good harvests over the last few seasons.
	These soils are prone to compaction and waterlogging if managed poorly

Component	1	2	3
Proportion of soil-landform unit	30%	40%	30%
CLIMATE Rainfall (mm)	Annual: 640
Temperature (^oC)	Minimum 8, Maximum 19
Precipitation less than potential evapotranspiration	October-March
GEOLOGY Age and lithology	Quaternary basalt, clay, sand and gravel; minor Neogene marine sand
Geomorphology	6.1.5 Alluvium, terraces, floodplains, lakes, swamps and lunettes of the Volcanic Western Plains
LANDUSE	Uncleared: Nature conservation; water supply Cleared: Cropping (cereal); sheep and beef cattle grazing
TOPOGRAPHY Landscape	Swamps and depressions
Elevation range (m)	66-302
Local relief (m)	0-10
Drainage pattern	Deranged
Drainage density (km/km²)	2.3
Landform	Alluvial plain
Landform element	Depressions	Swamp	Undulating plain
Slope and range (%)	1 (0-2)	1 (0-2)	2 (1-4)
Slope shape	Straight	Straight	Convex
NATIVE VEGETATION Ecological Vegetation Class	Plains Sedgy Wetland (0.7%), Stony Rises Herb-rich Woodland (0.5%), Aquatic Herbland / Plains Sedgy Wetland Mosaic (0.3%)
SOIL Parent material	Basalt derived alluvium; clay, silt and sand	Basalt derived alluvium; clay, silt and sand	Basalt derived alluvium; clay, silt and sand
Description (Corangamite Soil Group)	Grey and black clays (31)	Grey and black clays (31)	Grey and black clays (31)
Soil type sites	CLRA48, CLRA15, SFS2	CLRA48, CLRA15, SFS2	CLRA48, CLRA15, SFS2
Surface texture	Light clay	Light clay	Light clay
Permeability	Low	Very low	Low
Depth (m)	>2	>2	>2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Uniform expansive clays; high to very high water holding capacity and nutrient holding capacity depending on depth. Sodic subsoils, surface soils may be self-mulching. Low site drainage. Susceptibility to waterlogging.	Uniform expansive clays; high to very high water holding capacity and nutrient holding capacity depending on depth. Sodic subsoils, surface soils may be self-mulching. Low site drainage. Susceptibility to waterlogging.	Uniform expansive clays; high to very high water holding capacity and nutrient holding capacity depending on depth. Sodic subsoils, surface soils may be self-mulching. Low site drainage. Susceptibility to waterlogging.

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