The Extent and Potential Area of Salt-affected Land in Western Australia Estimated Using Remote Sensing and Digital Terrain Models

Abstract

A number of ways of mapping, monitoring and predicting salt-affected land have been used, all of which have strengths and weaknesses. In WA, methods that have been used include ABS surveys, extrapolating from detailed catchment mapping, groundwater levels coupled with soil-landform maps (NLWRA methodology) and satellite remote sensing and digital terrain models ('Land Monitor' - this paper). The ABS method may underestimate the extent of salinity whereas catchment mapping and the NLWRA method overestimates its extent and hazard. The Land Monitor method estimates that about 821,000 hectares were affected by secondary salinity (greater-than 1996) and this area had increased by about 14,000 ha per annum since 1989. The area with a salinity hazard (ie may develop salinity in future depending upon controlling factors) is estimated to be up to 5.4 million hectares of total land (between 2.8 and 4.4 million hectares of agricultural land). The results indicate that there may be less land at risk and more time to develop innovative plant and engineering solutions than was previously thought. The Land Monitor method has advantages in that it shows where salinity is within catchments and hazard areas at the regional scale are identified more efficiently than in any other method. In addition, the method is repeatable and allows confidence limits to be placed on the estimates.