A multi-scenario ensemble streamflow forecast method for Amu Darya River Basin under considering climate and land-use changes

Abstract Land-use and climate changes have the significant impacts on hydrological processes for river basin. In this study, a multi-scenario ensemble streamflow forecast (MESF) method is developed for analyzing the streamflow variation under considering climate and land-use changes, through incorporating CA-Markov model, global climate model (GCM) and Soil and Water Assessment Tool (SWAT) model within a general framework. The MESF method has advantages in (i) it can simultaneously assess the impacts of land-use and climate changes on streamflow; (ii) it can obtain the possible trend and range of future streamflow changes by analyzing multiple scenarios and ensemble forecast results; (iii) by analyzing the streamflow process under extreme scenarios, it can examine the effects of specific factors on streamflow. The MESF method is applied to the upper reaches of the Amu Darya River Basin in Central Asia where land-use and climate changes impacts research is urgently needed. Totally 72 scenarios under different land-use patterns, GCMs and Representative Concentration Pathways (RCPs), are analyzed. Ensemble forecast results reveal that (i) during 2021-2050, the average annual precipitation and the average annual temperature would both increase, and the mean annual streamflow would decrease; (ii) compared to land-use effects, climate change has more obvious effects on the streamflow (with contribution of 78.8% ∼ 98.7%); (iii) among all factors of land-use change, glacier melting triggered by climate warming is the most prominent factor; (iv) the peak flow within a year would have a tendency to shift from summer to spring in the future.