Analysis of the variation in potential evapotranspiration and surface wet conditions in the Hancang River Basin, China

Evapotranspiration is an important component of the water cycle, and possible trends in evapotranspiration can, among others, influence water management and agricultural production. Potential evapotranspiration (ET(p)) is a measure of the ability of the atmosphere to remove water from the surface through the processes of evaporation and transpiration. It plays an important role in assessing regional dry–wet conditions and variations in meteorological conditions. This study analyzed the change trends of monthly ET(p) and surface dryness and wetness in the Hancang River Basin and, through principal component analysis and correlation analysis, explored the main meteorological factors that affected ET(p) and the interactions between meteorological factors; ET(p) values were estimated using the FAO-56 Penman–Monteith method. The results showed that there was a large gap in ET(p) between different months in the Hancang River Basin, with a trend of first increasing and then decreasing within a year. The highest monthly evapotranspiration was 114.119 mm (July), and the lowest was 42.761 mm (January). The maximum relative humidity index was 0.822 (August), and the minimum was -0.979 (January). The average temperature, precipitation, average relative humidity, and solar radiation are positive factors that affect ET(p), while average air pressure is a negative factor that affects ET(p). This study provides a reference for the wet conditions of small watersheds and for countermeasures to address climate change.