NDVIによる蒸発散量推定手法の乾燥地灌漑農業地帯への適用について

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This paper examines the applicability and limitations of NDVI-based evapotranspiration estimation method using satellite imagery, applying at arid and semi-arid irrigated agricultural regions for regional water resources management purposes. NDVI-based ET estimation method has been regarded as a low-accuracy estimation method. However, this study shows that the method can estimate ET with high accuracy, by appropriate operation by understanding the characteristics and performance of the method. In a dry land in western United States, NDVI-based method estimated average field ET of the measure crops of the area; alfalfa, bean, sugar beet, corn, potato and wheat, in very high accuracy (3% error), which shows that NDVI-based method has a great potential of contribution on water resources management. However, the method is not good at estimating "daily" ET from "individual" agricultural field, because NDVI cannot evaluate the soil wetness and the simple NDVI-based ET equation is optimized to average field condition of the region. Accuracy of seasonal ET was high (12% error) even for individual agricultural field.