Dryland salinity in south-western Australia: its origins, remedies, and future research directions

Abstract

Replacement of deep-rooted, perennial native vegetation with shallow-rooted, annual agricultural plants has resulted in increased recharge causing shallow saline water tables leading to dryland salinity and loss of agricultural production. Restoring the vegetation by regeneration or replanting lowers water levels locally but field evidence and computer modelling suggests this needs to be widespread for regional effects, which conflicts with the future of conventional agriculture. Alley farming allows agriculture to be continued in the bays between the rows, but needs as much perennial, preferably deep-rooted, vegetation as possible in the bays to achieve the required recharge reductions. Where the asset to be preserved is valuable and a means of safe saline effluent disposal exists, pumps and drains will be part of any salinity management system, but where these conditions are not met they will be of limited use on an economic basis. To limit the spread of dryland salinity substantial change in farming systems is required and farmers need assurance that the recommended strategies will have the desired effect. Computer modelling is the only timely way to do this. An operationally simple 1-dimensional model already exists, and a 2-dimensional one is under development and testing. Three-dimensional modelling is also probably required to support strategic, intensive interventions. computer modelling, revegetation, engineering, perennial.

Quantifying the catchment salt balance: An important component of salinity assessments

“…The objective of this study was to quantify the salinity fluxes in the 152-km 2 Sandspruit catchment.…”

“…[9][10][11] According to De Clercq et al 11 , changes in land use over the last century or more, from extensive pastoral use to intensive cropping, have triggered the same process of salt mobilisation and decantation that is so widespread in Australia. 2,5,12,13 The Sandspruit catchment, a tributary of the Berg River, has particularly been impacted by dryland salinity. 11 According to Flügel 9 the total salt output from the Sandspruit catchment in 1986 was 8052 t, of which a third may be accounted for by atmospheric deposition.…”

“…Climatic controls are largely a function of proximity to the coast. 2 Human-induced or secondary salinisation may either be a function of the direct addition of saline water to the landscape and/or water resources, e.g. through industrial effluent and/or saline irrigation water, or it may be a result of a change in the water balance (quantity and dynamics) of a catchment causing the mobilisation of stored salts (dryland/non-irrigated salinity).…”

“…Ultimately, however, the salt balance provides an indication of the severity of the salinity problem in an area. The objective of this study was to quantify the salinity fluxes in the 152-km 2 Sandspruit catchment, including the quantification…”

Environmental change: prospects for conservation and agriculture in a southwest Australia biodiversity hotspot

“…For larger rivers, with headwaters in the drier northern parts of the region, additional planting of native vegetation in the upper catchment can further lower groundwater levels and reduce salinity (Clarke et al 2002, Bari et al 2004. Although revegetation will also reduce flow, ecologically it is more important to return rivers to freshwater systems.…”