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Abstract
An accurate estimate of the evapotranspiration (ET) and crop water productivity (WP) at the regional scale plays a significant role in managing water-saving irrigation in the dry region. Three sites in the Gezira scheme representing research field (Gezira Research Station, GRS), farmers' fields with participatory water management approach (Abdelhakam block) and ordinary farmers' fields (Madina block) were selected to estimate spatial ET, crop yield and WP of wheat using remote sensing data coupled with ground observations. The methodology is based on surface energy balance to estimate sensible and latent heat fluxes by combining remotely sensed data from Landsat 7 ETM+ and Moderate Resolution Imaging Spectroradiometer (MODIS) with common meteorological data. A comparison between Surface Energy Balance Algorithm for Land (SEBAL) estimated ET and ET calculated based on reference evapotranspiration (ETo)-crop coefficient (k c) approach over the growing season exhibited a good agreement. The average SEBAL-based ET of wheat for the entire season at GRS was 396 mm. SEBAL estimated k c were 0.46, 1.07 and 0.3 at the initial, mid season and late season stages, respectively, whereas the k c values determined from water depletion measurements were 0.5, 1.15 and 0.5, respectively. The average crop yield at GRS, Abdelhakam block and Madina block were 2.4, 1.9 and 1.4 t ha−1, respectively. The mean values of WP for the three locations were 0.52 (coefficient of variation, CV = 0.31), 0.50 (CV = 0.33) and 0.43 (CV = 0.45) kg m−3, respectively. Achieving a coefficient of variation (CV = 0.15), water savings at the three locations could reach 21%, 42% and 53%, respectively.
Acknowledgements
The authors are highly grateful to the Japan Society for the Promotion of Science (JSPS) for supporting this research. The authors also wish to thank the anonymous reviewers for their valuable comments and suggestions.