Prediction of future runoff in the Lancang River Basin based on CMIP6 under climate change

The Lancang River Basin (LRB), functioning as a pivotal transboundary hydrological system, has persistently maintained its runoff variability as a focal point of hydro-political concern among downstream riparian states This study identified five best-performing models (FBMs) from the 32 Coupled Model Intercomparison Project Phase 6 (CMIP6) models, prioritizing their precipitation and temperature simulation performance. Utilizing multi-model ensemble (MME) outputs from FBMs, we projected future precipitation and temperature changes under four future scenarios (SSP1–2.6, SSP2–4.5, SSP3–7.0, SSP5–8.5). These climate projections served as critical forcing data for hydrological modeling, enabling systematic analyses of interannual variability and seasonal runoff patterns across distinct future periods. Furthermore, the study quantitatively disentangled the relative contributions of precipitation and temperature to runoff changes. The results indicated that the FBMs demonstrate significantly enhanced simulation capabilities following systematic bias correction procedures. The MME projections reveal predominant increasing trends in both precipitation and temperature across the basin. Under four scenarios, future runoff is projected to increase at rates of 3.4 mm/10a, 1.7 mm/10a, 1.8 mm/10a e, and 2.5 mm/10a, respectively. Multiyear mean runoff estimates indicate increases relative to the base period (1995–2014) of 20.5 %-23.4 % for the near-term (2025–2040), 21.1 %-25.7 % for the mid-term (2041–2060), and 22.7 %-25.4 % for the long-term (2081–2099). Seasonally, spring runoff exhibits the most pronounced increases (+60.8 %), followed by winter (+54.6 %), with more moderate growth in autumn (+15 %) and summer (+12.3 %). The discussion revealed that during the period from 1961 to 2020, precipitation contributed to a 28.9 mm decrease in runoff, while temperature variations induced a marginal 0.5 mm increase. • Five best-performing models for the Lancang River Basin were identified from the 32 CMIP6 models. • Both projected future precipitation and temperature demonstrate increasing trends. • Future runoff is projected to increase, with the most pronounced growth occurring in spring, followed by winter. • Precipitation changes resulted in a 28.9 mm decrease in runoff within the Lancang River Basin, while temperature variations contributed to a 0.5 mm increase.