Combining the Crop Coefficient of Winter Wheat and Summer Maize with a Remotely Sensed Vegetation Index for Estimating Evapotranspiration in the North China Plain

Abstract

Estimates of actual evapotranspiration (ETc) in the wheat and maize fields are essential in effective planning of irrigation water use in the North China Plain. A widely used method for ETc estimation in agriculture is crucially dependent on the determination of crop coefficient curves. Estimating the coefficient coefficients from vegetation index (VI) is useful for regional ETc simulation because the VI can represent the actual crop conditions and capture the spatial variability. In this study, the basal crop coefficient and soil evaporation coefficient were combined with the commonly used VI obtained from satellite sensor based on the observed data from a flux tower. The basal crop coefficient had a fairly good linear relationship with the VI, and the soil evaporation coefficient was well related to the vegetation fraction, which was calculated from the VI. Using the VI-derived crop coefficient curves, ETc can be well simulated by a widely used ETc estimation method. Moreover, simulation of ETc was improved by the VI-derived basal crop coefficient curves. The new relationships between the crop coefficients and VI employed in the dual crop coefficient approach have great potential in the estimation of regional ETc in the region.