Wind Erosion in Western Queensland Australia

Chapter 3 – Modelling Land Erodibility Review3.2.2 Revised Wind Erosion Equation (RWEQ)The Revised Wind Erosion Equation (RWEQ) was designed to predict soil loss due to winderosion at sub-annual time scales. RWEQ combines empirical and process-based modelcomponents that became available following the development of WEQ. While WEQ providesestimates of annual soil loss, RWEQ can be applied to calculate the sediment transport massat specific field lengths, as well as average and maximum soil loss within a field. A majordevelopment in RWEQ was the incorporation of management factors to describe soil surfaceconditions, vegetation state, and soil moisture changes due to irrigation (Fryrear et al., 1998;Fryrear et al., 2000).The general input structure of RWEQ is similar to WEQ; however, the integration of modelcomponents reflects developments in field and wind tunnel studies that allowed for inputconditions to be modelled (Fryrear et al., 1998). The inclusion of a scheme to compute soilsurface conditions reflects these developments. Input variables of RWEQ include ER, the soilerodible fraction computed from soil properties; SCF, a soil crust factor computed from soilclay and organic matter content; WF, a weather factor; field size; COG, the crop type andorientation; and Hills, a factor used to modify wind speeds depending on field slope andheight. The model computes soil loss by the expression:( WF.EF.SCF.K COG)Qmax p= 109.8'.(3.2)where Q maxp is the maximum amount of soil that can be transported downwind in an event.While RWEQ can be run at variable temporal resolutions, the model computes soil loss on anevent basis. The input variables are computed by empirical relationships derived from fieldstudies on agricultural soils, but also still rely on the measurement of field conditions prior tomodel application. The model requires inputs of soil conditions, as well as land type and landuse, tillage/crop information, crop type, type of tillage tool, and amount and date of irrigation(Fryrear et al., 2001). The soil erodibile fraction EF (%DA