Dealing with salinity in Wheatbelt Valleys - Department of Water

Commander, Schoknecht, Verboom and Caccetta
WHEATBELT VALLEY SOILS
General distribution of Soils
The Northern and Southern Zones of Ancient
Drainage (Figure 9), as defined by the soil-landscape
mapping conducted by the Western Australian
Department of Agriculture, are characterised by a
gently undulating plateau, wide divides, long gentle
hillslopes, and broad valley floors 2 – 10 km wide
which have been in-filled by alluvium and colluvium.
Drainage is into chains of salt lakes on valley floors
which are a remnant of an ancient drainage system
that flows only in very wet years. The valley floors
have very low gradients, often 1:500 or less. The
western boundary of the zone is the Meckering Line
(Mulcahy 1967, Moore 1998).
Figure 9: Soil-landscape zones of South Western Australia
– 12 –
The Northern zone of Ancient Drainage is, in
essence, characterised by yellow sandy earths on
interfluves (Figure 10a) and red calcareous clays and
loams in the valleys (Figure 10b). By contrast, the
Southern zone of Ancient Drainage contains more
Sandy Duplexes (Figure 10c).
The valley floors of the zones of ancient drainage
have been simplified and divided into three broad
landscape categories, idealised in Figure 11. The
general distribution of each landscape category is
discussed and described in terms of the Soil Groups
of Western Australia (Schoknecht 1999) and the
original soil series described in the several soillandscape
and soil mapping publications covering the
Wheatbelt.