estimating and validating wheat leaf water content with three modis spectral indexes: a case study in ningxia plain, china

water content plays an important role in the process of plant photosynthesis and biomass accumulation. many methods have been developed to retrieve canopy leaf water content from remote sensing data. however, the validity of these methods has not been verified, which limits their applications. this study estimates the leaf water content (lwc) of winter wheat with three most widely used indexes: normalized difference water index (ndwi), simple ratio (sr), and shortwave infrared perpendicular water stress index (spsi), as well as modis short wave and near infrared data, and then compares remote sensing estimates of vegetation water content with field-measured values measured in concurrent dates. the results indicate that the three indexes are significantly correlated with the lwc of winter wheat at the 0.01 significance level. they all have good accuracy with higher than 90%. the indexes derived from modis bands 6 and 2 were better than those from bands 7 and 2 for measuring wheat leaf water content, and the correlations of the former two (ndwi and sr) were stronger than that of spsi.