An integrated assessment of runoff dynamics in the Amu Darya River Basin: Confronting climate change and multiple human activities, 1960–2017.

• Annual runoff change impact factors were analyzed based on the Budyko framework. • The elasticity coefficients of runoff exhibited spatio-temporal changes. • Human activities, particularly reservoirs construction for cropland expansion impacted runoff changes the most. The fragile ecosystem of the desiccated Amu Darya River Basin (ADRB) has experienced profound local hydrological havoc. These changes are associated with temperature, evapotranspiration, precipitation, and human-induced effects. However, previous long-term analyses have inadequately addressed these problems at the basin scale. Therefore, this study applied the elasticity coefficient method coupled with the water balance and Budyko framework, using hydro-meteorological observation data from three stations (Termez, Atamurat, and Kiziljar) to assess the long-term (1960–2017) runoff dynamics within the ADRB. The findings revealed that runoff at the three stations decreased at rates of −0.52 mm/a, −0.80 mm/a, and −0.97 mm/a, respectively, during the study period. Additionally, the relative contribution of climate change to runoff reduction ranged from −14.25% to −5.43%, while that of human activities exceeded 100% at all three stations. In addition, the total population across the basin has doubled within 33 years to approximately 80 million people, coupled with an expansion of cropland areas at a rate of 42.6%, corresponding to a net increase of 2,520,249 ha. Furthermore, the construction of reservoirs that were implemented before cropland expansion activities reduced the amount of water flowing downstream since runoff needs to be stored before being released for irrigation. This demonstrates that long-term runoff reduction was mainly due to human activities, with construction of reservoirs for cropland expansion being the most direct factor. The study findings provide essential information for water resource management in the ADRB. More attention should be paid to the construction and operation of reservoirs, and sustainable cropland development should be implemented for improved ecological environment. [ABSTRACT FROM AUTHOR]