Abstract
In order to perform large scale afforestation of arid land aiming at fixation of the atmospheric carbon dioxide, it is necessary to clarify the water balance and the level of salt accumulation in arid land. In this study, the residence time of the water (water age) on surface soil was related to the salt concentration of the soil. The model which can show the salt distribution and water balance in a large area was developed by using the relation of water age and salt concentration. The optimal afforestation area was estimated by the model. Moreover, effect of the measure to prevent a runoff on the water balance was estimated. This model was verified by the data measured in an experimental arid land in Western Australia. Furthermore, the creek water played an important role for the afforestation.
