Attribution analysis of future seasonal runoff variations and quantitative assessment of uncertainty sources in the source area of the Lancang River, China

Climate change and human activities jointly affect the hydrological cycle of rivers. Quantifying the contributions of climate change and human activities to future runoff changes and assessing the impact of uncertainty sources on future runoff changes are crucial for water resource management. Taking the source area of the Lancang River (SALR) as the research area, this study constructed a framework that integrated a global climate model (GCM), shared socioeconomic pathway (SSP), hydrological model (HM), seasonal Budyko model, and variance analysis (VAAN). This framework was adopted to explore the contributions of climate change and human activities to the future seasonal runoff changes in the SALR, and to quantify the influence degree of uncertainty sources on the attribution results of future seasonal runoff changes. The main conclusions were as follows: (1) The mutation year of runoff depth in SALR was 2008. (2) Both the ABCD and DWBM hydrological models can accurately simulate runoff variation processes in SALR. (3) Human activities are the dominant factor influencing the future runoff changes in the spring, summer and autumn of SALR, contributing 5.63–18.96, 3.10–16.18, and 4.26–16.51 mm, respectively, to runoff increases under different SSP scenarios, respectively; while climate change is the dominant factor influencing the future winter runoff changes of SALR, contributing 2.30–8.79 mm to runoff increases. (4) The interactions among HM, GCM, and SSP are the dominant factors influencing the uncertainty of the attribution analysis results of future runoff changes, accounting for over 68.64% of the total variance (within the ensemble framework comprising 2 HMs, 3 GCMs, and 3 SSPs).