Central Asia Chu River East Asia SWAT Schrenk spruce (Picea schrenkiana Fisch. et Mey.) Tianshan Mountains Weihe River annual streamflow annual water yield boreal forest canopy filtering climate change climate variability climate warming closed canopy cumulative effects extreme weather events flood flow regimes forest disturbance forest disturbances forest floor forest hydrology frequency analysis fruit tree planting gap-edge canopy groundwater level headwater stream high flow high flows