Dealing with salinity in Wheatbelt Valleys - Department of Water

Although the waterlogged area under the present
regime with the presence of the reserve will be 29%
of the total area of the sub-catchment including the
reserve, if the area of the reserve is excluded from
consideration, the waterlogged area would be more
than 60%. While surface and groundwater discharge
from this sub-catchment is very low compared to the
other sub-catchments due to the presence of the
reserve, similar rises of water levels occurred in the
cleared areas of the catchment. As these areas are in
the lower parts of the landscape and in higher risk
areas, the percentage area that will be waterlogged is
much higher compared to the other catchments.
This clearly illustrates the fact that although planting
part of a catchment to trees will reduce surface and
groundwater discharge, yet the process of
salinisation in the other parts of the catchment will
continue largely unabated.
Morrell, Hatton and Curry
The results of FLOWTUBE modelling for
Flowtube#3 and Flowtube#4 showed similar
patterns of water level rise to Flowtube#1 and #2.
FLOWTUBE modelling was combined with HARSD
techniques to calculate the areas where water level
will be within 1–2 m from the surface under the
different management options (Table 1). The results
show that under present recharge regimes, 45–50%
of catchment areas will be waterlogged
(groundwater 1-2 m from the surface) after 40 years.
Reducing the recharge rates to 20 mm, the affected
areas will be 27% in single stream catchments, 37%
in multiple catchments and 40% in nine minor
catchments that are adjacent to the lake system. On
the other hand, reducing the recharge rate to 10
mm, the waterlogged area will be 17% in single
stream catchments, 26% in multiple streams and
32% in minor catchments.
Table 1: Percentage of land becoming waterlogged (groundwater 1–2 m from the surface)
after 40 years under recharge scenarios of 10, 20, 40 and 60 mm yr –1
Scenario Flowtube #1 Flowtube #2 Flowtube #3 Flowtube #4
10 mm 17 21 (46) 26 32
20 mm 27 26 (57) 37 40
40 mm 45 29 (64) 50 49
60 mm 55 30 (66) 55 53
Uniform 40 mm – 57 – –
(a) no recharge was applied on the reserve area for recharge scenarios 10–60mm;
(b) for a uniform recharge of 40 mm the reserve was cleared. Values between brackets are
percentage of waterlogged area in the sub-catchment excluding the area of the reserve
Figure 7: Lake Chinocup Land Monitor Map of Salinity 1997
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