Evaluation of WAPOR Evapotranspiration Product for Citrus Orchard in South Mediterranean Region

Increasing water scarcity in the Mediterranean region is enhanced by deficiencies in irrigation management and climate changes. Accurate determination of crop water consumption would be useful to improve irrigation water efficiency and productivity. The measurements of crop water requirements are based on observations, which are expensive, and the data analysis is challenging. Developed tools like water productivity through open access of remotely sensed derived data (WaPOR), providing free and fine-scale information, might help to improve irrigation water management. However, evaluation of this tool in local conditions is essential for complex agricultural systems. This study aims to evaluate the actual evapotranspiration (ETa) estimated by the WaPOR tool using local ETa observations of eddy covariance (EC) for a citrus orchard in the Cap Bon region north east of Tunisia. The drip-irrigated navel orange orchard covers 0.4 ha which is planted in 1998 at a density of 500 trees/ha. The study is conducted for 4 years (2014–2018). The dataset used is quite rich and characterized by the variability of climatic and hydric conditions, including periods of drought and floods. The obtained ETa using WaPOR is at a spatial resolution of 100 m. The monthly ETa values are extracted from one pixel covering the eddy covariance station. The monthly averaged ETa EC ranges from a minimum of 52 mm to a maximum of 126.7 mm, while values estimated by WAPOR range between 38 and 122 mm. The result of the comparison of both methods shows a close value during summer. WaPOR can be considered as a promising approach to spatialize evapotranspiration for citrus orchards.