|The most commonly used explanation for the development of dryland salinity relates to deep-rooted, perennial, native vegetation being replaced with shallow rooted, introduced vegetation - ie. annual crops. Consequent reduction in evapotranspiration and water interception allows more water to move through the soil profile to the groundwater (ie. recharge). This results in a rise in water levels, and stored salt is mobilised to the surface, via capillary rise, forming a salt crust.
Development of dryland salinity model - before and after clearing:
Picture of the Stavely Hills taken in 1865, with the eastern section of the Grampians showing in the distance. Source: Ken Brain.
|"Clearing of native vegetation has exposed discharging springs and saturated soils to the mechanical damage by grazing. Subsequently the permeability and soil stability of the discharge zones has been decreased by erosion and the mobilisation and subsequent precipitation of Fe and Sulphur rich compounds. Chemical processes impedes the ability of the seep to discharge, forcing discharging water from the fractured rock spring to discharge around the seep. Clearing has created an environment where a cycle of chemical reactions further enlarge the discharge zones and accelerate erosion." (Fawcett, J., et al,1999)
Discharge area in eastern Dundas Tablelands
Close up of discharge area (photo: CLPR)