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Prediction of Salinity Intrusion Due to Sea Level Rise and Reduced Upstream Flow in the Gbm Delta

Author(s): Rabeya Akter; Sumaiya Sumaiya; Mashrekur Rahman; Tanveer Ahmed; Mohiuddin Sakib; Anisul Haque; Md. Munsur Rahman

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Keywords: Salinity intrusion; GBM delta; Salinity variation; Salinity modeling

Abstract: Sea level rise owing to global climate change and change of upstream river flow is expected to change salinity levels in the rivers of deltaic Bangladesh. Landward push of estuarine salinity front is both detrimental to the delicate ecosystem of Bangladesh, as well as threatening to its ecological sustainability. Recent salinity data in the Ganges-Brahmaputra-Meghna (GBM) delta shows a consistent increase of salinity in the rivers and estuaries of the region. In this paper, both present-day condition and future scenarios of salinities in the rivers&estuaries of the GBM delta are computed by applying the Delft 3D model. Measured salinity data at some specific locations are used to calibrate and validate the model. Future scenarios of salinity is computed by generating‘scenarios’for future upstream discharge and downstream sea level conditions including impact of sea level rise. Upstream discharge scenarios are constructed from a basin scale hydrological model, and the downstream sea level scenarios are constructed from an ocean model. The scenario results indicate that the maximum salinity in the western part of the region, where ecologically sensitive Sundarban is located, will exceed 25 ppt; which is considerably higher than recommended levels for many Sundarban-dependent species. However, unlike present-day condition, eastern and central estuarine system faced alarming salinity intrusion, 6-7 ppt increase in mid-century and 13-14 ppt increase in end of the century.

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Year: 2016

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