Attribution analysis of runoff change based on Budyko-type model with time-varying parameters for the Lhasa River Basin, Qinghai–Tibet Plateau

The Lhasa River Basin (LRB), Qinghai–Tibet Plateau (QTP), China This study investigates the application of three Budyko-type models with time-varying parameter and further explore the attribution of runoff change in the QTP. Three Budyko models with time-varying parameters estimated by linear, quadratic, sine and linear stepwise regression equations have been applied and compared their adaptability. According to the comparison results, the sensitivity decomposition analysis has been utilized based on the best-fitted Budyko model to separate the impacts of climate change and human activities on runoff during the 1988–2015 period. This study is aiming at exploring the pattern of the regional hydrological cycle and improving our understanding of the driver mechanism of runoff change in the alpine mountain area. The time-varying Budyko-type models significantly improve the performance of runoff simulation compared to constant Budyko-type models, while the Choudhury–Yang model performs best, and the sine equations of simulated parameter ω best reflects the time variation pattern of parameters, which declares that ω have certain periodic characteristics. The result of runoff attribution shows that precipitation is the main factor increasing runoff before 2003 and human activity variables mainly lead to the decreasing trend of runoff after 2003, while PDO and PNA affect the runoff-generated process through the relationships with the environmental variables in the LRB.