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Waterlogging and Salinity
Saline and waterlogged soils, saline creeks and rising water
tables collectively represent one of Australia’s biggest
environmental catastrophes.
Since effective salinity control will generally require a
large investment and may take many years to assess, it is
important to try and understand as much as possible about
the cause(s) of salinity problems.
Dryland and irrigation salinity result from a groundwater
problem. Increasing waterlogging and salinity are just the
symptoms resulting from a hydrological imbalance that may
be occurring at a catchment scale or in a localised area.
In Australian farming areas this imbalance is largely caused
by the clearing of perennial trees and shrubs and their replacement
with annual crops or pastures unable to utilise and absorb
as much rainfall as trees. Water that is not used by the plants
or stored in the soil surface may percolate below the root
zone into the groundwater. The recharge under a pasture or
crop may be 10 to 100 times that which occurred under the
native forest that it replaced.
Once a saline watertable nears the surface, water is evaporated
which increases the salt concentration in the soil profile,
with salt often left on the surface. The combined effect of
waterlogging and increased soil salinity is devastating for
most plants. Agricultural productivity declines and native
vegetation can be destroyed. The result is not only reduced
farm productivity but also damage to infrastructure and loss
of native flora and fauna that depend on it. The problem is
complicated by the effect of soil type, geology, the presence
of barriers to water flow or even underground streams. Because
salinity commonly affects many farmers and businesses in a
particular catchment, government support may be available
to investigate the actual processes causing the problem and
opportunities for controlling the rise and flow of water within
a catchment.
Planting
Trees to Reduce Salinity & Waterlogging
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