The interactions between land, vegetation, and climate are highly complex and there are few demonstrations of the many potential combinations of treatments which could be used to combat dryland salinity. For this reason, computer simulations are used. This is the first of 2 papers that describe the results of computer modelling of revegetation strategies to reduce land and water salinisation in the western wheatbelt of Western Australia. A distributed parameter, physically based, cellular, 2-layer, mathematical model was used to simulate the effect of a variety of treatments. Modelling predicted that if current land use continues, 40% of the cleared area will become saline. Modelling replacement of the annual pasture with a deep-rooted perennial pasture or pristine native vegetation prevented the onset of salinity, but block or alley treatments always left a significant residual saline area and seepage even at the highest density of revegetation modelled. Combining remnant vegetation in pristine condition, 60-m-spaced tree belts and deep-rooted perennial pasture in mainly the upper mid-slope bays between tree belts reduced saline land to 10% of the cleared area and seepage volume to 30% of the untreated case. The second paper describes the impact of faults on treatment effectiveness.