Soil/Landform Unit - Douglas lakes and lunettes

Looking south down the Douglas Depression with Lake Copper Colour (kidney shaped lake to left), North Lake, Central Lake and White Lake the major lakes further south

Area: 5759 ha

0.25% of CMA region

Within the Douglas Depression are a number of lakes and

lunettes

that vary from saline to freshwater in nature. As part of the salt lake depression of the North Western Dunefields and Plains, the soils of the lakes and lunettes include seasonally wet soils that are

sodic

yellow and grey texture contrast (

Hydrosols

) in lakes and grey to brown cracking clay soils (

Vertosols

) on plains and lunettes. The soils are very susceptible to seasonal inundation and waterlogging. Cracking clay soils have friable surfaces that can be vulnerable to

compaction

at critical moisture contents. Land use on these playa plain complexes is dryland cropping and grazing, while nature conservation is also a major use owing to high salinity levels and seasonally wet states. There are a number of woodland vegetation communities including Heathy Woodland, Low Rises Woodland, Lignum Swampy Woodland, Plains Woodland and Salt Paperbark Woodland. Other vegetation communities include Ridged Plains Mallee, Samphire Shrubland, Red Gum Wetland, Plains Savannah, Saline Lake Mosaic and Inland Saltmarsh.

Looking north up the Douglas Depression towards Mt Arapiles
	Saline lake within the Douglas Depression

Component	1	2
Proportion of soil-landform unit	70%	30%
CLIMATE Rainfall (mm)	Annual: 460

Temperature (^oC)	Minimum 8, Maximum 21
Precipitation less than potential evapotranspiration	October–April
GEOLOGY Age and lithology	Quaternary paludal silt and clay; Quaternary fluvial silt, sand and minor gravel (Shepparton Formation); Quaternary aeolian dune sand (Lowan Sand)

Geomorphology	5.3.3 Salt lake depression of the North West Dunefields and Plains
LANDUSE	Uncleared areas: nature conservation; water supply Cleared areas: sheep grazing; water supply

TOPOGRAPHY Landscape	Lake and lunettes

Elevation range (m)	104–174
Local relief (m)	0–1
Drainage pattern	Centripetal–dendrtic
Drainage density (km/km²)	1.3
Landform	Lake and lunettes
Landform element	Playa/lunette complex including water bodies	Gently undulating plain
Slope and range (%)	4 (1-7)	5 (2-9)
Slope shape	Concave	Straight to convex
NATIVE VEGETATION Ecological Vegetation Class	Plains Woodland (14.1%), Plains Savannah (13.2%), Salt Paperbark Woodland/Samphire Shrubland Mosaic (13.1%), Ridged Plains Mallee (12.3%), Other (43.5%)

SOIL Parent material	Swamp deposits (sand, silt and clay), evaporites and aeolianites, aeolian dune sand and clay	Marine sand and silt, fluvial silt, sand and minor gravel

Description (Corangamite Soil Group)	Seasonally wet soils: sodic yellow and grey texture contrast soils (33)	Grey and brown cracking clay soils (37)
Soil type sites	NA171, NA141, NA178	LS3, LSWW9, LSWW5
Surface texture	Sand	Medium clay
Permeability	Slow	Slow
Depth (m)	> 2	> 2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS Critical land features, processes, forms	Susceptible to seasonal inundation, waterlogging and ultimately soil salinity. Upper soils susceptible to sheet erosion and wind erosion when exposed.	Susceptible to inundation and waterlogging in lower areas. Surface soils friable and only slightly susceptible to wind erosion. Soils susceptible to compaction at critical moisture contents.

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