Evapotranspiration estimation in Jeddah using FAO and Hargreaves methods

The purpose of this study was to compare two well-known techniques for calculating evapotranspiration (ET₀), which is an important component of the hydrological cycle, particularly in arid and semi-arid areas such as Jeddah, Saudi Arabia. The simplified, temperature-dependent Hargreaves equation and the physically based FAO Penman-Monteith equation (PME) were the main subjects of the study. Reference ET₀ was calculated using daily meteorological data from station 41024 (1997-2011), which included temperature, humidity, and wind speed. PME produced more detailed and typically higher ET₀ values since it took into account a wide range of climatic factors, according to the analysis that compared the estimates from the two methodologies. The Hargreaves approach, which just used temperature, on the other hand, generated estimates that were lower and less variable. This study provides these results in context by contrasting them with earlier studies, such the work done by Al-Subhi (2012) utilizing Dalton's equation. The results illustrate the necessity for reliable ET₀ estimation techniques in water-scarce ecosystems subject to climatic extremes, underscoring the crucial balance between data availability and estimation accuracy.