Effects of coniferous plantation thinning on annual interception evaporation: Model verification

For evaluating the effect of coniferous plantation thinning on water resources, our previous study (Komatsu et al., 2007c) developed a model for predicting changes in annual evapotranspiration caused by coniferous plantation thinning. This model is comprised of transpiration and interception evaporation parts. The model needs to be verified from three viewpoints, stability of transpiration amounts with thinning, decrease in interception evaporation amounts with thinning, and applicability of the model to catchment scale. This study mainly focused on verification of the interception evaporation part. Based on seven datasets of interception evaporation derived from earlier publications, we compared model prediction results with the observed results. Model prediction results agreed fairly well with the observed results, indicating validity of the interception evaporation part of the model. Based on one dataset for verifying applicability of the model to catchment scale, model prediction results agreed fairly well with the observed results, implying applicability of the model to catchment scale. We should note that validity of the transpiration part of the model was not examined. Applicability of the model to catchment scale was not fully examined due to lack of observation data. Thus, we raised observation data that should be required for further model verification and presented guidelines for future observation studies.