Identification of the Saline Free Zone in Southwest Region of Bangladesh by Limiting Salinity Level (< 1ppt) with Improved Flow Scenarios Using Mathematical Modeling

The coastal area of the Ganges delta in Bangladesh is characterized by tides and salinity from the Bay of Bengal. Salinities in the Bangladesh coast are dependent on the annual rainfall, evaporation, freshwater flows discharging from upstream and the impact of climate change. Average salinity concentrations at the coast are higher in the dry season than in the monsoon, due to reduction in freshwater flow from the upstream. The higher salinity levels have adverse impacts on agriculture, aquaculture, domestic and industrial water use and so on. Hence, the simulation of the calibrated salinity model is carried out in this study to investigate the baseline condition of salinity and assessment of hydrodynamic condition which will reduce the salinity level at downstream portion of Southwest region of Bangladesh. Historical data and field measurements on salinity, water flow, water level and numerical modeling technique are applied to develop the hydrodynamic scenarios (mainly based on upstream discharge condition), which are simulated with the calibrated and validated hydrodynamic and salinity model. The scenario with increase in upstream flow through Ganges connected rivers is simulated to identify the saline free zone at the most south end zone. The simulation of the calibrated salinity model is carried out by limiting salinity level (< 1ppt) with improved flow scenarios by mathematical modeling technique. The saline free zone with different flow scenarios is assessed by MIKE One-Dimensional (MIKE 11) and MIKE Two-Dimensional (MIKE 21FM) Modelling system