Afforestation is one of the most promising methods for the fixing of carbon dioxide. In this research, a target area of unused land, not competitive with food production and with a large area, was selected in the arid land near Leonora in Western Australia. It was necessary to select suitable tree species for afforestation in the target arid area. The objective of this work was to establish a method for the estimation of the amount of water used per net carbon intake. In this study, a method for the estimation of the water use efficiency (WUE) using nutrient tracers is suggested and established. Calcium was the most suitable nutrient for use as a tracer for this estimation method. The sampling strategies for the measurements were decided, and the nutrient concentrations in the tree organs and sap and content of carbon were determined. In particular, a method through which the calcium content in the sap is corrected using the calcium concentration in the organs of a tree was examined. It was confirmed that the WUE value obtained with this method was comparable to those determined by conventional methods. Finally, it is suggested that the present method for WUE determination is characterized by the advantages of short measurement terms and low cost.