5 th International Conference on Water & Flood Management (ICWFM-2015) 547 ASSESSMENT OF CHANGE IN FUTURE WATER RESOURCES OF BRAHMAPUTRA BASIN APPLYING SWAT MODEL USING MULTI- MEMBER ENSEMBLE CLIMATE DATA Supria Paul 1* , AKM Saiful Islam 2 , Mohammad Alfi Hasan 3 and Md. Mostifizur Rahman 4 1 Institute of Water and Flood Management, Bangladesh University of Engineering and Technology, Dhaka-1000, Bangladesh, e-mail: paulwre710@gmail.com 2 Institute of Water and Flood Management, BangladeshUniversity of Engineering and Technology, Dhaka-1000, Bangladesh, e-mail: akmsaifulislam@iwfm.buet.ac.bd 3 Institute of Water and Flood Management, BangladeshUniversity of Engineering and Technology, Dhaka-1000, Bangladesh, e-mail: mdalfihasan19@gmail.com 4 Institute of Water and Flood Management, BangladeshUniversity of Engineering and Technology, Dhaka-1000, Bangladesh, e-mail: mostafizsust@gmail.com ABSTRACT Bangladesh is a delta formed by sedimentation from the Ganges, the Brahmaputra and the Meghna rivers and its distributaries and tributaries. Among these three major rivers, the Brahmaputra carries the highest (about 67%)annual flow to Bangladesh from China, India and Bhutan. In order to assess the water availability and predict floods in Bangladesh, it is necessary to establish a hydrologic model over the Brahmaputra basin. In this study, a physical based model SWAT has been set up over the Brahmaputra basin. The model has been calibrated and validated using the observed daily flow data at Bahadurabad from 1998 to 2007. Rainfall data from three gridded global standard data products, namely, TRMM, APHRDOTIE and GPCP, have been used to simulate the model.It has been found that TRMM data are more accurate than APHRODITE and GPCP. After calibrationg the model,SWAT has been simulated for dry,wet and extreme ensembles of PRECIS model for 2020s,2050s and 2080s. It has been found that the percentange of monsoon flow will increase to4-15% and the pre-monsoon flow will increase to25-92% at the end century. Keywords:Brahmaputra, Climate model, flow, GBM basin, Satellites data, SWAT 1. INTRODUCTION The Ganges-Brahmaputra-Meghna (GBM) river system plays an important role in China, Bhutan, India, Nepal and Bangladesh. The GBM basin is the third largest freshwater outlet to the world’s ocean (Chowdhury et al., 2004). The Brahmaputra river contributes the 67% of the total annual water flow of Bangladesh (Immerzeel, 2008). The peak discharge of the Ganges slows down the drainage of the Brahmaputra river through the Baruria transit. This helps to increase the areal extent, depth and duration of flood in the Brahmaputra basin because the Brahmaputra water cannot be drained out quickly (Mirza, 2011). This river basin is the main source of water in Bangladesh. Assessment of stream flows through this river can play a vital role for the water management of the country. However, estimation of water scarcity or water availability depends