, 2004). We then quantified the sensitivity of the hydrological variables such as total water yield, soil water content, ET, streamflow, and groundwater recharge to a group of various climate change scenarios including changes in CO2 concentration, temperature, and precipitation. We assessed the long-term patterns in the hydrological variables with Phase 3 of the Coupled Model Intercomparison Project (CMIP3) downscaled precipitation and downscaled Integrated Model to Assess the Global Environment (IMAGE) land use change scenarios for the 21st century under the A1B and A2 scenarios (Nakicenovic and Swart, 2000). In brief, the A1B storyline assumes a future world of very rapid economic Proteases inhibitor growth, low population

growth, and rapid introduction of new and more efficient technology with the development balanced across fossil fuel and non-fossil fuel energy sources. In contrast, the A2 storyline assumes a very heterogeneous world where population growth is high, economic development is primarily regionally oriented, and per capita economic growth and technological change are more fragmented and slower than in A1B. The Brahmaputra is a transboundary river and the world’s

fourth largest in terms of the average discharge at the mouth, with Selleckchem SAHA HDAC a flow of ∼20,000 m3 s−1 (Jian et al., 2009) (Fig. 1). Originating in the glaciated Kailas range of southern Tibet at 5300 m amsl (above mean sea level), the Brahmaputra traverses 1625 km in China and 918 km in India, before flowing 337 km through Bangladesh and discharging into the Bay of Bengal (Singh et al., 2004). The total drainage catchment of the river is 519,500 km2 (82°–98° East, and 23°–32° North), of which 50.5% is in China, 33.6% is in India, 8.1% is in Bangladesh and 7.8% is in Bhutan (Immerzeel, 2008). The Tibetan Plateau divides the basin into two distinct climatic zones: (1) the mountain climate, characterized as cold and dry, dominates the northern part of the basin; and (2) the tropical Chlormezanone monsoon climate that dominates the southern part is characterized as warm and humid, and receives high amounts of widespread precipitation, mainly under the influence of the Indian summer monsoon

(Singh et al., 2004). The Brahmaputra basin is physiographically diverse and ecologically rich in natural and crop-related biodiversity. The basin is divided into three distinct physiographic zones: (1) the Tibetan Plateau that covers 44.4% of the basin area with elevations above 3500 m amsl, (2) the Himalayan belt that covers 28.6% of the basin area with elevations ranging between 100 and 3500 m amsl, and (3) the lowland floodplains that cover 27% of the basin area with elevations below 100 m amsl (Gain et al., 2011). Average temperature and precipitation in the basin vary by these physiographic zones. Typically, December and January are the coldest months, and the period from May to August includes the warmest months of the year.