Using SAR Data to Detect Wheat Irrigation Supply in an Irrigated Semi-arid Area

The objective of this study was to use SAR (sensitivity of Synthetic Aperture Radar) data to detect the supply of irrigation water during the anthesis and grain-filling phenological stages of wheat in the irrigated Tadla perimeter of Morocco. Backscattering coefficients were derived from four ERS-1 (European Remote-Sensing Satellite-1) images acquired between 31 March and 12 April 2011 and were compared with the irrigation water invoices database. The analysis showed that there were significant changes in backscattering values caused by irrigation, with average values ranging between 0.11 and 3.11 dB. A reference level of 0.52 dB was established for differentiating between (recently; up to 4 days) irrigated and non-irrigated plots. We also set an interval of 5 days for the acquisition of SAR images in order to ensure continuous monitoring of the irrigated wheat plots over time. The study showed that radar data contain important information for the assessment of irrigation supplies during the cropping season, which could help regional decision-support systems to monitor and control irrigation supplies over large areas.