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

Land-use and climate changes have 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 advantages of MESF are as follows: (i) it can simultaneously assess the impacts of land-use and climate changes on streamflow; (ii) it can obtain the possible trend and the range of future streamflows through ensemble forecast under multiple scenarios; (iii) based on analysis of streamflow processes under extreme scenarios, it can examine the effects of key factors on streamflow. The MESF method is applied to the upper reaches of the Amu Darya River Basin in Central Asia. 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, but the mean annual streamflow would decrease; (ii) compared to the impact of land-use change, 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 in one year would have a tendency to shift from summer to spring due to the rising temperature and the speeding up snow melt.