IMPACT OF CLIMATE CHANGE ON RAINFALL IN JAMUNESWARI RIVER BASIN (BANGLADESH)

Abstract

Bangladesh is prone to different types of floods with different magnitudes because of its unique geographical location and topography. Teesta river sub-basin in the North-western part of Bangladesh is more vulnerable to flood if compared to other parts. In this context ten rainfall stations from Jamuneswari catchment were considered to downscale the impact of climate change on rainfall. During rainfall data during 1966 to 2008 of all the ten stations were obtained from Bangladesh Water Development Board. Length of wet and dry series, mean monthly rainfall and annual rainfalls along with their variances were used for validatingLARS weather generator.. LARS-WG uses the semi empirical distribution for generating the synthetic data series. The Kolomogorov-Smirnov (KS)- test was used to test whether the synthetic data and the observed data follow the same distribution within 95% confidence level or not. Various random number seed values were used to fmd the correct population for all the stations for wet and dry series mean monthly series. Selection of random seed goes in heuristic manner using KS test. After several trials, the random seed value was finalised to generate the synthetic data belonging to the same distribution and population. The work was taken forward to generate the daily rainfall for climate scenarios A1B, A2 and B 1 as given in IPCC report. LARS WG supports analysis with 15 GCMs. The analysis was carried out using all scenarios and all GCMs for periods were 2011-2030 (centered at 2020), 2046-2065 (centered at 2055) and 2080-2099 (centered at 2090). The analysis of the data shows that the uncertainty in the prediction increases with the increase in the timescale. It is also .found that the variability in the predictions is smaller in annual values followed by seasonal and monthly analysis. The ensemble of annual rainfall for various scenario and GCMs shows increased annual rainfall at all the station with a maximum at iii ABSTRACT Mahipur (5%). Ensemble of seasonal and monthly analysis show that most of the GCM are in agreement for changes in monsoon season (JJA). The changes vary within the range of 5 to 10%. ry