It would seem that the presence of chloride sufficient to restrict crop water extraction could only increase the chance of deep drainage
under zero tillage.
Here, P is rainfall, and S is the surplus lost as surface runoff and/ or deep drainage
, on day n.
Assuming transient state conditions, deep drainage
was calculated as:
The soil tends to produce both high runoff and high deep drainage
under annual cropping, due to the low water-holding capacity of the Kandosol.
is one portion of the water balance that is being examined closely as part of improving water use efficiency in irrigation agriculture (Radford et al.
50 m, and represents a significant capacity to both store water during wet periods, but also to lose that water via deep drainage
before utilisation by a crop root system.
Summer-dominant rainfall areas such as the QMDB have been considered to have a lower risk of deep drainage
than the winter-dominant rainfall zones of southern Australia, because a greater proportion of annual rainfall coincides with high potential evaporation (SalCon 1997; Walker et al.
Use of water balance models is expanding rapidly, in estimation of biomass and crop yields where runoff estimation maybe less important, and in runoff and deep drainage
estimation where runoff estimation is important.
A key driver for the conversion of a high salinity hazard to a salinity risk is an increase in deep drainage
(potential groundwater recharge) with change in land use from native vegetation to cropping or grazing (Scanlon et al.
There have been a number of studies of deep drainage
under native vegetation in the low rainfall areas of southern Australia (e.
Conversion of 5 points, construction of a new stump track with 160 m length, track renewal on about 1 600 m, built deep drainage
on about 600 m length.
Irrigated agriculture in Australia, and the cotton industry in particular, have become increasingly aware of water losses due to deep drainage
(DD, expressed as nun/ha where 100mm/ha = l ML/ha) in furrow-irrigated Vertosols (Silburn et al.