Spatiotemporal Dynamics of Longterm Actual Evapotranspiration in Afghanistan

Afghanistan contains an irrigated area of approximately 3 million ha, with the remainder consisting of rainfed regions. Agriculture, as the primary consumer of water resources, contributes significantly to the national GDP. The irrigated area undergoes variation from year to year, depending on the availability of water. To understand the variations in actual water consumption by the agriculture sector, it is vital to assess the long-term spatiotemporal variations in actual evapotranspiration (AET) across the country. This study assesses the long-term variation in AET (1983-2023) and its implications for water resource management under changing climate. Utilizing the Global Land Evaporation Amsterdam Model (GLEAM) v4.1 dataset, this study investigates long-term AET trends and their relationship with precipitation. Employing statistical methods such as the Mann-Kendall trend test and Spearman's correlation, the study determines the relationship between AET and precipitation over time. The findings emphasize critical seasonal and spatial patterns, with regions such as the eastern and northeast parts of Afghanistan, AET has increased significantly over time, while in the southern and southwest regions, AET has declined, exacerbated by recurrent droughts. Furthermore, a decline in AET was observed in October in the Northern River Basin and in August in the Harrirod-Murghab River Basin, while an increase was noted in March and May in the Panj-Amu River Basin. Correlation analyses revealed intricate interactions between precipitation and AET, influenced by factors such as groundwater extraction and soil moisture dynamics. A positive correlation was identified between AET and precipitation in northeastern and central regions, while a negative correlation was observed in southwestern and southern areas. These findings provide a foundation for the development of sustainable water management strategies tailored to Afghanistan's distinct hydrological and climatic conditions, offering broader applications for arid and semi-arid regions facing similar challenges.