Computer modelling of the effect of revegetation strategies on salinity in the western wheatbelt of Western Australia 2. The interaction between revegetation strategies and major fault zones

This is the second of 2 papers to describe computer modelling of the effect of revegetation strategies on land and stream salinity in the wheatbelt of Western Australia and deals with the impact that the higher hydraulic conductivity within major fault zones has on the effectiveness of revegetation treatments. Increasing the hydraulic conductivity by factors of 5 or 10 increases saline seepage by about 140% or 160%, respectively, for most treatments. For a treatment to have the same effect with the fault as without it requires an increase of 50% in the number of tree rows. This has major consequences for the management of water resources, as ignoring faults seriously underestimates the problem. Increasing the hydraulic conductivity has only a fairly small effect on the area of salinised land, an increase of up to 4% of the cleared area. However, tree-row spacing may need to be reduced by two-thirds to have the same effect as would be expected without the fault. Thus, although the change in salt land area is relatively small, the fault still has a big impact on the density of treatments necessary to get the same effect, which has some consequences for land managers.