Calculating Spatiotemporal Distribution of Evapotranspiration of Winter Wheat Using the Landsat-8 imageries

Abstract

【Objective】 Evapotranspiration is not only an important hydrological process but also a key parameter in irrigation management. Understanding its spatiotemporal variation at regional or catchment scales is essential to improving water resource management and sustaining agricultural production. This paper aims to present a method using air-born imageries to estimate variation in evapotranspiration of winter wheat field. 【Method】 The region we studied is Liangyuan District at Shangqiu City, Henan Province. From the Landsat-8 imageries, we extracted the planting areas of winter wheat using the supervision classification method combined with the threshold method. The evapotranspiration was estimate by the surface energy balance system (SEBS) model, from which we analyzed the spatiotemporal variation in the evapotranspiration. 【Result】 Compared with ground-truth data, the overall accuracy of the extracted winter-wheat planting areas was 88.0%, with its associated Kappa coefficient being 0.75. Winter wheat accounted for 66.85% of the cropland land and 43.96% of the total land in the studied region. The evapotranspiration varied seasonally, with the seasonal average decreasing from summer to winter. The evapotranspiration varied as the crop grew, with crop demand for water increasing during the sowing, tillering, jointing, and heading stages, while decreasing during the harvesting stage. Overall, the magnitude of the evapotranspiration at different stages is ranked in the following descending order: heading stage > jointing stage > harvest stage > sowing stage > tillering stage. 【Conclusion】 The Landsat 8 imagery can be used to estimate daily evapotranspiration from winter wheat field at regional and catchment scales, helping improve irrigation and water resource management.

Keywords

• landsat-8
• sebs
• evapotranspiration
• winter wheat