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It should not be surprising that with a landscape as variable as that in Australia that management for salinity should also vary. While increased recharge due to the change from native vegetation to current agronomic practices is the cause of secondary salinity, its reversal is more complicated. Management options Management options generally fall into three broad categories. Choosing the most appropriate category depends on the type of groundwater flow system. 1. Biological recharge reduction This will generally involve more perennial leaf cover across broad areas of the landscape. Its effectiveness will depend on the level of recharge reduction required to control trends, how quickly the groundwater flow system responds to the reduced recharge as well as social and economic factors such as profitability, skills, etc. These first two biophysical factors are intrinsically linked to the type of groundwater flow system; generally with upland local groundwater flow systems being more viable to this type of option. If a 50% recharge reduction is seen to be effective, this may be feasible through a change in the current enterprise e.g. phase farming, opportunity cropping, alley farming etc. On the other hand, if a 90% recharge reduction is needed, this implies a very major change of land use. * See: A revolution in land use: emerging land use systems for managing recharge by R. Stirzaker et al., 2000. Effectiveness of current farming systems in the control of dryland salinity by G. Walker et al., 1999. Available from CSIRO Publications If the response time is 200 years, important assets such as urban areas, ecosystems and water resources may need to be protected in the meantime. 2. Engineering options to control groundwater discharge These options usually consist of surface water drainage, sub-surface drainage and groundwater pumping. Viability depends on the conductivity or transmissivity of the deposits (i.e. dependent on the groundwater flow systems), costs of maintenance and options for the disposal water. 3. Living with salt Increasing levels of salt in some areas is inevitable and hence there is a need to adapt to this more saline environment. * See: NDSP OPUS database of dryland salinity projects NDSP TOOLS for managing dryland salinity |
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