Title: A mixed-level factorial inference approach for ensemble long-term hydrological projections over the Jing River Basin

Journal: Journal of Hydrometeorology

DOI: https://doi.org/10.1175/JHM-D-21-0158.1

Abstract: Long-term hydrological projections can vary substantially depending on the combination of meteorological forcing dataset, hydrologic model, emissions scenario, and natural climate variability. Identifying dominant sources of model spread in an ensemble of hydrologic projections is critically important for developing reliable hydrological projections in support of flooding risk assessment and water resources management; however, it is not well understood due to the multifactor and multi-scale complexities involved in the long-term hydrological projections. Therefore, a stepwise clustered Bayesian (SCB) ensemble method will be first developed to improve the performance of long-term hydrological projections. Meanwhile, a mixed-level factorial inference (MLFI) approach is employed to estimate multiple uncertainties in hydrological projections over the Jing River Basin (JRB). MLFI is able to reveal the main and interactive effects of the anthropogenic emission and model choices on the SCB ensemble projections. The results suggest that the daily maximum temperature under RCP8.5 in the 2050s and 2080s is expected to respectively increase by 3.2 °C and 5.2 °C, which are much higher than the increases under RCP4.5. The maximum increase of the CARM-projected changes in streamflow for the 2050s and 2080s under RCP4.5 is 0.30 and 0.59 × 10³ m³/s in November, respectively. In addition, in a multimodel GCM-RCM-HM ensemble, hydroclimate is found to be most sensitive to the choice of GCM. Moreover, it is revealed that the percentage of contribution of anthropogenic emissions to the changes in monthly precipitation is relatively smaller, but it makes a more significant contribution to the total variance of changes in potential evapotranspiration and streamflow.