Spatiotemporal trends of reference evapotranspiration in Algeria

Reference evapotranspiration (ET0) is a key variable for understanding the water cycle and is essential for managing water resources in arid and semi-arid regions. Employing the high-resolution CRU TS version 4.05 gridded datasets and utilizing a substantial network of 48 meteorological gauging stations, this analysis spans a temporal scope from 1901 to 2018, offering valuable insights into ET0 trends. The results of the Mann-Kendall test show that the majority of stations exhibit a significant upward trend in ET0, with the strongest trends observed in June (Z = 5.58), July (Z = 6.21), and August (Z = 4.42). The magnitude of the trend is found to be faster in the eastern region, with the maximum values observed in May and July. The upward trend in ET0 is significant throughout all seasons and is most notable in summer at southern stations, while in winter, the trend is more prominent at northeastern stations. Annual ET0 trends are highest in the northeastern parts of the South, like Biskra (Z = 8.65), El Oued, and M’sila (Z = 8.54). However, the lowest was observed in Adrar, Tamanrasset, and Ghardaia provinces. Factors such as changes in air temperature, net radiation, wind speed, relative humidity, and land use may influence ET0 levels. These findings provide insights into the changes in water requirements for plants and soil surface evaporation over time, which can have implications for water resource management in Algeria.