Padma Multipurpose Bridge Project

location specific data was available for Mawa location. But under the CLASSIC Project (IWFM andCEGIS, 2008) grid discharge were simulated at different fine grid locations using the following GSMand RCM Models, from where the Mawa location was included. CCCma’s GCM, CGCM2 CCSR/NIES’s GCM, CCSR/NIES AGCM GFDL’s GCM, R30 Hadley Centre’s GCM, HadCM3 Hadley Centre’s RCM, PRECIS Hadley Centre’s RCM, HadRM220. Mean monthly flow situation derived from the above-mentioned models for Padma Bridge locationis analyzed. It was found that minimum flow may be observed during the month of April (7,478 cumec,derived from HadRM2 for Year 2030), which was 7.8% lower than the base (year 1990) year meanflow. On the upper side, maximum flow was observed during the month of September (70,690 cumec,derived from PRECIS model for Year 2050) which was 5.35% more than that of base year mean flowfor September 4 .5.4.2.2 High Flows21. Maximum mean daily to seasonal flow was observed from GFDL model (Year 2030) inputscenarios. Mean daily maximum discharge was found as 82,260 cumec, which varied within the rangeof 76,220 to 82,000 cumec over the weekly to seasonal time periods. Large flood peak was observedfrom the HadCM3 input model. Peak discharge was observed as 151,100 cumec which was around58% higher than the base period discharge. Non-exceedance probability of the peak discharge wasfound as 90.42% 5 .22. Combining the net effect of sea level rise and increased precipitation at Mawa, for 1 in 10 yearreturn period event (RP-90), the observed and predicted water level due to sea level rise and increasein rainfall was found as 6.81 mPWD and 7.44 m PWD respectively.5.4.2.3 Low Flow23. Mean daily minimum discharge was found as 7,366 cumec, which varied within the range of7,377 to 7,719 cumec over the weekly to seasonal time periods. Extreme low flow peak was observedfrom the same input model where the peak low flow was observed as 7,345 cumec, which was around3.4% lower than the base period discharge. Non-exceedance probability of the extreme low flow wasfound as 98.71% 6 .5.4.2.4 Salinity Intrusion24. Sea level rise and reduced dry season river discharges will result in increased salinity in theMeghna estuary and in the lower reaches of the Meghna River. It was shown by WARPO (2005) thata maximum sea level rise of 1.0m sea level rise by 2100 would result in the 5 ppt isohaline “front”moving roughly 60 km upriver, or to a point about 70 km below the bridge. Thus the risk of salinityintrusion in the Padma Bridge site may be considered insignificant enough to exclude fromenvironmental impact assessment.5.5 Identification of Mitigation/Adaptive Measures5.5.1 GHG Management Plan25. Based on the estimates of GHG emissions from the Project compared to the overall global GHGemissions (50 billion tons of CO 2 equivalents per year, 2004 estimates 7 ) is insignificant and hencedoes not warrant further analysis and any mitigation measures.4 Same as previous5 Same as previous6 Same as previous7 IPCC Fourth Assessment Report: Climate Change 2007: Mitigation of Climate Change5-7