Although the climate and land use change scenario impacts yielded relatively low increases of 2% and
Protein Tyrosine Kinase inhibitor 4% in the annual streamflow of the Brahmaputra River, the large variations in seasonal streamflow relative to the baseline were predicted by the SWAT model, confirming that the seasonal variability would increase as a result of changes in climate and land use (Table 6). Streamflow was predicted to decrease by 6% during the pre-monsoon months of February through April, and decrease by 19% and 20% during the early monsoon months of May through July under the A1B and A2 scenarios, respectively. These results agreed with the findings of Immerzeel et al. (2010) for the A1B scenario, but contradicted the findings of Gain et al. (2011), who predicted increased streamflow in all seasons for both A1B and A2 scenarios. The predicted decrease in streamflow during the dry period implied selleck kinase inhibitor that the effects of ET become more pronounced than glacial melt and snowmelt during the dry period. In contrast, compared to the baseline
scenario, streamflow was projected to increase by 14% and 18% during August through October and by 21% and 28% during November through January under the A1B and A2 scenarios, respectively (Table 6). The greatest differences were predicted to occur during the peak monsoon months of July and August. July streamflow was predicted to decrease by 19% (47,113–38,082 m3 s−1) and 20% (47,113–37,490 m3 s−1), and August streamflow was predicted to increase 12% (48,838–54,739 m3 s−1) and 16% (48,838–56,761 m3 s−1) under the A1B and A2 scenarios, respectively, compared to the baseline. These changes agree with the findings of previous research (Immerzeel, 2008) under the A2 scenario. The streamflow between November and
January was predicted to increase from an average of 9913–12,038 m3 s−1, and 12,727 m3 s−1 under the A1B and A2 scenarios, respective increases of 21% and 28% compared to the baseline. The winter streamflow was also predicted to increase in the Brahmaputra basin under the A1B and A2 scenarios (Gain et al., 2011). These relatively large predicted increases during the winter months could possibly be the result of increased snowmelt and more precipitation either in the form of rainfall due to the increase in winter temperature. Similar climate change impacts in winter streamflow were also reported for the upper Mississippi River basin in the United States (Jha et al., 2006). The substantial projected increases in water yield, soil water content, and streamflow as impacts of climate and land use change yielded increased groundwater recharge in the Brahmaputra basin (Fig. 6f). The groundwater recharge was predicted to increase by 47% and 49% annually under the A1B and A2 scenarios, respectively (Table 6).