Abstract: As a countermeasure against global warming, large scale afforestation of arid land has been done by fixing atmospheric CO 2 into plants. In arid land, however most of the rainwater is lost by runoff and evaporation. Effective use of rainwater is required for afforestation. Thus, we made an original runoff model to evaluate water distribution in a research area. In this study, we report determination of parameters in the original runoff model with Digital Elevation Model (DEM) to estimate water movement for the selection of afforestation place. From the comparison of actual and numerical results, the two sensitive parameters were decided and the characteristics of runoff water movement were elucidated hydrologically. Moreover, validation on expansion of mesh size for application of this model in large scale area was done. However, numerical results with large size mesh hadn't been approximated to small size mesh, because of roughness information of large size mesh. It was our assignment of future investigation. Keywords: Afforestation, DEM, Mesh size, Runoff, Simulation Introduction For the mitigation of global warming issue, a large scale afforestation of arid land has been promoted to fix atmospheric carbon on land which is not effectively used. Arid land area is huge in the world but the most important problem is lack of water for afforestation because of the small amount of rainfall and occurrence of runoff on soil surface. Most of runoff water is evaporated without using for plants, therefore, it is necessary to use runoff water effectively for arid land afforestation. The authors have demonstrated the improve the land condition for afforestation by introducing artificial technologies The purpose of this study is to estimate the distribution of runoff water by using the original runoff model for selection of the best afforestation places. In this report, two sensitive parameters in the original runoff model were decided to estimate water movement for the selection of afforestation place. Moreover, expansion of mesh size by using our model was validated to calculate in large scale area
