EVALUATION OF FAO’S WATER PRODUCTIVITY PORTAL (WAPOR) YIELD OVER THE BEQAA VALLEY, LEBANON

Abstract

With the increasing pressure of agriculture on water and land, achieving high water productivity is essential. Models such as FAO’s Water Productivity Portal (WaPOR) aim to estimate water productivity by providing yield and evapotranspiration. In this study, the aim was to validate the yield product of WaPOR in the Beqaa Valley, Lebanon. The study was focused in two main fields. Yield of Potato and wheat, planted during 2017-2018, was validated in one field. In addition, the yields of barley, vetch, barley/vetch mixed fields and vetch/oat mixed fields, planted during 2012-2019,were validated in the other field by comparison against farmer reported yields. Statistical Indicators such as percentage relative error (RE), Root Mean Square Error (RMSE),R2 , correlation (r), and bias were used for this validation. Wheat yield showed better results at a resolution of 30 m than that at a 100 m where recorded RE% of 1.14% < 20%, R2 of 0.38, RMSE of 0.71 ton/ha, r of 0.61 and a bias of 0.68 ton/ha versus an RE%|-12.43%| <20%, R2 of 0.38, RMSE of 1.2 ton/ha, r of 0.62, and a bias of 0.73 ton/ha respectively. For the other crops, level consistency could not be tested for since not all crops where equally identified at the different levels. Potato yield was considerably accurate at a 100m resolution with RE% of 19.55%<20%, an R2 of 0.22 and RMSE of 9.31 ton/ha, r of 0.47, and a bias of 2.39 ton/ha. As for barley,vetch,barley/vetch and vetch/oat mixed fields results were considered to be poor with a RE% > 20% for all crops at both levels 2 and 3. This inaccuracy in crop yield estimations was attributed to inaccuracy in farmer reported yields which was detected in both fields, the standardized LUE max, harvest Index and moisture content.