Quantitative relationships among potential evapotranspiration, surface water, and vegetation in an urban area (Baghdad)

Potential evapotranspiration (PET) is the amount of water that evaporates from land, surface water and plant transpiration. Based on monthly surface water and vegetation cover areas derived from Sentinel-2 imagery and precipitation records from Baghdad station for the two years 2018 and 2019, the quantitative relationships such as PET versus water area, PET versus vegetation area and PET versus precipitation were investigated. Using Origin 9.2 program, a new multiple regression model was derived to estimate the monthly mean PET in dry and wet months. To improve the accuracy of the model, monthly errors, bias and mean absolute error were calculated to approximate reasonable estimates of PET. Based on this statistical analysis, the best value of about -1 mm/day should be added to the proposed model as a correction term.