Water Resources Vulnerability to Climate Change with Special Reference to Inundation

Vulnerability of water resources considered changes in flooding conditions due to combination of increased discharge of river water during monsoon period and sea level rise for the two projection years, 2030 and 2075. MIKE11, a fixed bed hydrodynamic model, was used for the estimation of changes in river water level which was coupled with Geographic Information System (GIS) for the estimation of extent of flooding. The climatic parameters for the baseyear 1990 was obtained from secondary sources and the changes of climatic parameters for the two projection years were obtained from the General Circulation Model (GCM) output. Values of these parameters were taken as input for MIKE11 model runs. Discharge values for 8 upstream boundary stations were calculated from a general relationship between changes in rainfall and runoff. The MIKE11 model also includes other parameters under development scenario that considered embanking the major rivers. Model runs gave water level values for over 4,000 output stations along the rivers all over the country except Chittagong and Chittagong Hill Tracts area. These water levels were interpolated by using GIS techniques to generate water depth spatial database for the study area. Water depth spatial database for each of the projection years was compared with that of the baseyear to find change in water depth. These values were then superimposed on “land type database” to estimate extent of flooding in terms of water depth. A combination of development and climate change scenarios revealed that the Lower Ganges and Surma floodplains would become more vulnerable compared to the rest of the study area. On the other hand, the north-central region would become flood free due to embankment in the major rivers.