Factors affecting dryland salinity in two wheat belt catchments in Western Australia

Abstract

We investigated why the Wallatin Creek Catchment in the Western Australian wheatbelt had an appreciable area of secondary salinity whereas the adjoining North Baandee Catchment had almost none. The Wallatin Creek Catchment, which is long and narrow, had a shallow regolith over granite bedrock. Although this catchment had less salt stored in the regolith than the wider North Baandee Catchment, the groundwaters came close to the ground surface because the regolith was thin and the valley cross-section narrow. Management practices which increase recharge (e.g. using level banks to control runoff), are likely to result in increased salinity in the short term in the Wallatin Creek Catchment. We also investigated whether retaining areas of remnant vegetation had reduced the amount of secondary salinity in a sub-catchment of the Wallatin Creek Catchment. At comparable positions in the landscape, groundwater levels were up to 7 m lower under the remnant vegetation. The vegetation appears to have delayed, if not prevented, the development of salinity in nearby and downslope areas.